Advances in the use of acidic potassium permanganate as a chemiluminescence reagent: a review.

Analytica Chimica Acta 807 (2014) 9–28

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Analytica Chimica Acta journal homepage: www.elsevier.com/locate/aca

Review

Advances in the use of acidic potassium permanganate as a chemiluminescence reagent: A review Jacqui L. Adcock, Neil W. Barnett, Colin J. Barrow, Paul S. Francis ∗ Centre for Chemistry and Biotechnology, Faculty of Science, Engineering and Built Environment, Deakin University, Waurn Ponds, Victoria 3216, Australia

h i g h l i g h t s

g r a p h i c a l

a b s t r a c t

• Analytical applications of acidic potassium permanganate chemiluminescence. • Discussion of emitting species and light-producing reaction pathways. • Influence of enhancers such as polyphosphates, formaldehyde and sulfite. • Clinical, forensic, food science, agricultural and environmental applications.

a r t i c l e

i n f o

Article history: Received 24 September 2013 Received in revised form 2 November 2013 Accepted 8 November 2013 Available online 18 November 2013 Keywords: Review Chemiluminescence Potassium permanganate Flow injection analysis High performance liquid chromatography Emitting species

a b s t r a c t We review the analytical applications of acidic potassium permanganate chemiluminescence published since our previous comprehensive review in mid-2007 to early 2013. This includes a critical evaluation of evidence for the emitting species, the influence of additives such as polyphosphates, formaldehyde, sulfite, thiosulfate, lanthanide complexes and nanoparticles, the development of a generalized reaction mechanism, and the use of this chemistry in pharmaceutical, clinical, forensic, food science, agricultural and environmental applications. © 2013 Elsevier B.V. All rights reserved.

Contents 1. 2.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . New insights into acidic potassium permanganate chemiluminescence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1. The characteristic red emission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2. Singlet oxygen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3. Polyphosphate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4. Generalized reaction mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5. Preliminary partial reduction of the reagent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6. Formaldehyde and related enhancers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

∗ Corresponding author. E-mail addresses: [email protected], [email protected] (P.S. Francis). 0003-2670/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.aca.2013.11.016

10 16 16 17 17 17 17 18

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J.L. Adcock et al. / Analytica Chimica Acta 807 (2014) 9–28

2.7. Fluorescent compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8. The oxidation of sulfite with and without enhancers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.9. Other sulfur compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.10. Lanthanide complexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.11. Nanoparticles and related materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Analytical applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1. Pharmaceutical and clinical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2. Forensic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3. Food and consumer products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4. Agricultural and environmental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Jacqui L. Adcock completed a Bachelor of Forensic Science (Honours) at Deakin University in 2003. Her PhD, received in 2008, included a comprehensive review of permanganate chemiluminescence and a series of experiments that elucidated the key light-producing pathways of permanganate reactions. Jacqui’s postdoctoral research has included the development of new applications of fast comprehensive twodimensional gas chromatography at RMIT University (Australia) and Firmenich (Switzerland), followed by a return to Deakin University as an Australian Research Council Postdoctoral Fellow (Industry) to examine enzymatic synthesis, microencapsulation and biological evaluation of a new class of omega-3 derived functional food ingredients.

Neil W. Barnett received a BAppSc from the Royal Melbourne Institute of Technology in 1978, a PhD from the University of Manchester in 1986 and a DSc from Deakin University in 2005. He is a fellow of both the Royal Society of Chemistry and Royal Australian Chemical Institute and is a member of the Australian Research Council College. As Professor of Analytical Chemistry in the Centre for Chemistry and Biotechnology at Deakin University, Neil leads a group investigating the chemistry and applications of chemiluminescence plus novel multidimensional liquid chromatography. He has published over one hundred and seventy papers in major international

18 18 19 21 21 22 22 23 23 25 26 26

Colin J. Barrow is Chair of Biotechnology and Director of the Centre for Chemistry and Biotechnology at Deakin University. He graduated with a PhD from the University of Canterbury in 1988 and has extensive industry and academic experience. Colin’s research is primarily focused on the processing and production of omega-3 lipids, and the use of nano-biotechnology to produce and utilize peptide and protein materials for a variety of industrial and medical purposes. He has approximately 150 peer-reviewed publications, several patents, has presented at numerous conferences, and is a founding member of the International Society for Nutraceuticals and Functional Foods (ISNFF).

Paul S. Francis received a BSc (Hons) in 1999 and a PhD in 2003 from Deakin University. He currently holds an Australian Research Council Future Fellowship, administered by Deakin University, with La Trobe University (Australia) and the University of Manchester (U.K.) as Host Institutions. Through this fellowship, Paul heads a large collaborative programme of research focussed on the development of new highly sensitive luminescence-based detection systems. He has over 100 publications and has been recognized by honours such as a Victoria Young Tall Poppy Science Award (The Australian Institute of Policy and Science), and the Robert Cattrall Medal (Royal Australian Chemical Institute).

journals.

1. Introduction Although the use of potassium permanganate in chemiluminescence reactions in acidic aqueous solution can be traced back to the early twentieth century investigations of Harvey [1] and Grinberg [2], the reagent was not exploited for analysis until Stauff and Jaeschke’s determination of sulfur dioxide in 1975 [3]. These and other researchers continued to explore the detection of inorganic species, but the predominant use of acidic potassium permanganate as a chemiluminescence reagent has become the detection of organic compounds, beginning with the determination of morphine by Townshend’s group in the mid-1980s [4–7]. In 2001, researchers from our laboratory prepared a review of acidic potassium permanganate as a chemiluminescence reagent, including its historical origins and a chronological account of analytical applications [8]. In 2007 we re-examined this area of research in another comprehensive review [9], with specific foci on reaction conditions, influence of enhancers, relationship between analyte structure and chemiluminescence intensity, and

the determination of pharmaceuticals, biomolecules, antioxidants, illicit drugs, pesticides and pollutants. In both reviews, we evaluated the often-conflicting proposals for the nature of the emitting species in light of contemporary evidence [8,9]. Since our last major review of this area, there have been over 170 new publications concerning the use of permanganate as a chemiluminescence reagent, which have expanded the scope of the reagent and provided new insight into the reaction mechanisms and emitting species. We now present a comprehensive account of both the fundamental understanding and analytical applications of acidic potassium permanganate chemiluminescence published from mid2007 up until early 2013, in journals indexed in the American Chemical Society’s Chemical Abstracts (accessed through SciFinder Scholar). This includes a significant number of Chinese language articles, which for completeness we have included in Tables 1–3. In our discussion, however, we have predominantly focussed on papers appearing in English language journals for reasons of correct interpretation of results. We have omitted discussion of chemiluminescent reactions with permanganate in alkaline

Table 1 Determination of organic compounds with acidic potassium permanganate chemiluminescence. For older applications, see Table 1 in Ref. [9]. Analyte

Enhancer

Instrumentation/comments

Matrix

Limit of detection

Ref.

Acetaminophen

Formaldehyde

Pharmaceutical formulations

1 × 10−10 M

[180]

Acyclovir ␤-Adrenergic agonists

Formaldehyde Sodium polyphosphate, sodium thiosulfate (added to permanganate solution)

FIA. Analyte inhibits the CL reaction of permanganate and formaldehyde FIA FIA (also separated with HPLC). Comparison of CL flow cells

Pharmaceutical formulations Not applied

[16] [157]

Albumin Albumin

Galangin, polyphosphoric acid Enhancement of CL reaction of permanganate with heterocyclic imidazole derivatives Rhodamine B, gold nanorods

0.06 mg L−1 (3 × 10−7 M) 4 × 10−9 M epinephrine 6 × 10−9 M isoprenaline 5 × 10−9 M metaproterenol 3 × 10−10 M salbutamol 1 × 10−10 M fenoterol 0.01 ␮g mL−1 (2 × 10−10 M) BSA 1 × 10−9 M (HSA) 4 × 10−10 M (BSA)

[111]

Pharmaceutical formulations Pharmaceutical formulations

2 × 10−10 M (HSA) 3 × 10−10 M (BSA) 6 × 10−9 g mL−1 (1 × 10−8 M) 300 ng mL−1 (2 × 10−6 M)

Urine

1.3 × 10−9 g mL−1 (4 × 10−9 M)

[121]

Albumin

Formaldehyde

Amoxicillin

3-(3 -Nitrophenyl)-5-(2 sulfonylphenylazo)-rhodanine Sodium polyphosphate, sodium thiosulfate (added to permanganate solution) Formaldehyde, cetyltrimethyl ammonium bromide Polyphosphoric acid Sodium polyphosphate

Amoxicillin

Andrographolide Aniline Antioxidants (screening) Antioxidants (screening)

Sodium polyphosphate

Antioxidants (screening)


Ascorbic acid Ascorbic acid

Formic acid

Ascorbic acid

3-(4 -Nitryl)-5-(2 -sulfonicphenylazo)rhodanine Glyoxal

Ascorbic acid Ascorbic acid Baicalin Benzylpenicillin Bismerthiazol

Batch analysis. Analyte inhibits by binding to nanorods FIA Comparison between SIA and multicommutated flow analysis. Permanganate immobilized in the detection area Flow analysis incorporating MIP column as the detection cell FIA

Serum

−9

[181] [182]

[183] [23]

Not applied

3 × 10

FIA


1 × 10−6 g mL−1 (3 × 10−6 M)

[184]

FIA HPLC (monolithic C18 column; gradient elution) HPLC (C18 column; gradient elution). UV-abs detection and two on-line antioxidant assays (CL and DPPH) HPLC (monolithic C18 column; gradient elution). Comparison with on-line radical-decolorization antioxidant assays

Natural waters Green and black tea

5 × 10−10 M Not stated

[185] [27]

Coffees

Not stated

[151]

Green tea, cranberry juice, thyme extract

[131]

M

[157]

FIA SIA. Permanganate temporarily immobilized on solid support microbeads in the detection zone. Coupled with fluorescence detection of vitamins B2 and B6 FIA

Tablets Multivitamin preparations

5 × 10−8 M epicatechin 8 × 10−8 M rosmarinic acid 1 × 10−7 M quercetin 5 × 10−7 M caffeic acid 4 × 10−7 M gallic acid 5 × 10−7 M rutin 3 × 10−9 g mL−1 (2 × 10−8 M) 9.1 ␮g mL−1 (5 × 10−5 M)

Foods

0.031 mg L−1 (2 × 10−7 M)

[187]

FIA. Analyte inhibits the CL reaction of glyoxal and permanganate FIA

Fruit and vegetables

5 × 10−13 M

[188]

Vitamin C tablets and foods

3 × 10

FIA FIA FIA

Not stateda Pharmaceutical formulations Water

2.5 × 10−8 g mL−1 (6 × 10−8 M) 0.40 mg L−1 (1 × 10−6 M) 8.9 ␮g L−1 (3 × 10−8 M)

−10

M

[186] [117]

[113] [189] [190] [191] 11

CdTe nanocrystals, sodium hexametaphosphate Formaldehyde Fluorescein Formaldehyde, polyphosphoric acid

Synthetic samples Serum


Aminopterin 5-Aminosalicylic acid (mesalazine)

FIA Flow analysis

12

Table 1 (Continued) Analyte

Enhancer

Buminafos Cannabidiol

Captopril, acetylcysteine and methimazole Carbazochrome

Sodium polyphosphate, sodium thiosulfate (added to permanganate solution) Glyoxal

Formadehyde

Catechin Catecholamines

Formaldehyde

Cefotaxime sodium Cefotaxime sodium Chemical oxygen demand

Polyphosphoric acid Glyoxal Glutaraldehyde

Cinnamic acid Clomipramine Colchicine Deltamethrin

Glyoxal Formic acid Formaldehyde CdTe quantum dots, Tween-80

2,4Dichlorophenoxyacetic acid Dihydroquinones

Matrix

Limit of detection

Ref.

Flow-analysis (multicommutation) with on-line photoreactor HPLC (C18 column; gradient elution)

Spiked irrigation waters and a soil

0.005 mg L−1 (1 × 10−9 M)

[166]

Industrial-grade hemp

1 × 10−6 M

[139]

FIA

Pharmaceutical formaulations

[192]

FIA after cation exchange solid-phase extraction FIA. Permanganate entrapped in silica sol–gel column IC (Ionpac CS12 column; aqueous mobile phase)

Pharmaceuticals and spiked urine

3.9 ng mL−1 (2 × 10−8 M) captopril 3.7 ng mL−1 (2 × 10−8 M) acetylcysteine 1.0 ng mL−1 (9 × 10−9 M) methimazole 2 × 10−10 ␮g mL−1 (9 × 10−16 M)

Multicommutated flow analysis system with reactants temporarily immobilized on microbeads in the detection zone FIA FIA Dissolved organic matter was digested by excess acidic permanganate. Remaining oxidant measured by CL reaction with glutaraldehyde in 96-well plate luminometer FIA FIA FIA Glass slides modified by quantum dots and MIP, inserted into 96-well microplate for commercial reader Irradiation of analyte before reaction with permanganate

Pharmaceutical formulations and spiked urine

−8

[193]

Spiked tea and coffee

4 × 10

Spiked human urine

4.7 ␮g L−1 (3 × 10−8 M) epinephrine 5.1 ␮g L−1 (3 × 10−8 M) norepinephrine 0.6 ␮g L−1 (4 × 10−9 M) dopamine 8 × 10−7 M

[64]

Pharmaceutical formulations Pharmaceutical formulations Natural waters and factory wastewater

1.9 ␮g mL−1 (4 × 10−6 M) 3.0 × 10−8 g mL−1 (6 × 10−8 M) 0.1 mg L−1

[194] [195] [22]

Spiked urine Pharmaceutical formulations Pharmaceutical formulations Fruit and vegetables

8 × 10−9 M 0.008 ␮g mL−1 (3 × 10−8 M) 3 × 10−8 M 0.018 ␮g mL−1 (4 × 10−8 M)

[48] [49] [196] [112]

Not stateda

3 mg L−1 (1 × 10−5 M)

[197]

Batch analysis

River waters

[198]

Ground and river water samples Pharmaceutical formulations Pharmaceutical formulations and spiked urine Plasma Pharmaceutical formulations

0.12 mg L−1 (1 × 10−6 M) (bottom of linear range) 3.1 × 10−8 g mL−1 (1 × 10−7 M) 1 mg L−1 (7 × 10−6 M) 1 × 10−8 M 2 × 10−8 M 3 × 10−8 g mL−1 (6 × 10−8 M)

[200] [44]

M

[30]

[118]

[34] [199] [63]

Dinitrobutylphenol Dopamine Dopamine

Se nanoparticles Formaldehyde

Batch analysis FIA FIA

Dopamine Doxorubicin (Adriamycin) DNA

Formaldehyde Formaldehyde

FIA FIA

Carbon dots dotted nanoporous gold signal amplification label Formaldehyde

Sandwich-type DNA hybridization reaction FIA

Serum

9 × 10−19 M

[116]

Eye drops

1 × 10−8 g mL−1 (3 × 10−8 M)

[201]

CdTe nanocrystals, sodium polyphosphate

FIA

Spiked tap water

6 × 10−11 M estradiol 4 × 10−12 M estriol 1 × 10−11 M estrone

[114]

Emedastine difumarate Estrogens


Cefadroxil


Fangchinoline Fenfluramine Fenoterol and tyrosine Ferulic acid Fluorouracil Fluorouracil, adriamycin, hydroxycamptothecin and mitomycin Flunarizine Formaldehyde

Sulfonophenylazo rhodanine derivative Sodium polyphosphate, sodium thiosulfate (added to permanganate solution) Glyoxal Formaldehyde Formaldehyde

Formaldehyde

Formaldehyde Sodium polyphosphate

Glutathione Haematin Heroin

Sodium polyphosphate Formaldehyde Sodium polyphosphate

Hydroxycamptothecin

Formaldehyde

Immunoglobulin G and thiomersal

Galangin, polyphosphoric acid

Indole derivatives

Formaldehyde

Indoleacetic acid


Radix Stephania tetrandra Weight loss capsules

0.078 ␮g mL−1 (1 × 10−7 M) 9.48 × 10−9 g mL−1 (1 × 10−8 M)

[202] [159,160]

Not applied

1 × 10−9 M fenoterol 4 × 10−9 M tyrosine

[29]

FIA FIA FIA

Taita Beauty samples Pharmaceuticals and spiked serum Not applied

1 × 10−8 M 3 × 10−8 g mL−1 (2 × 10−7 M) Not stated

[203] [41] [42]

FIA FIA. Analyte enhances CL reaction of permanganate and ninhydrin FIA. Analyte enhances CL reaction of permanganate and ninhydrin HPLC (C18 column; isocratic elution). Application to glutathione disulfide by thiol blocking and disulfide bond reduction FIA FIA SIA. Sample sandwiched between two CL reagents. An off-line hydrolysis step is used to convert heroin to morphine FIA

Pharmaceutical formulations Detergent products

8 × 10−7 g mL−1 (2 × 10−6 M) 0.637 ␮g mL−1 (2 × 10−5 M)

[204] [205]

Leather wastewater

4.6 × 10−4 ␮g mL−1 (2 × 10−8 M)

[59]

Cultured muscle cells

5 × 10−7 M

[95]

Not applied Chicken blood Seized drug samples

5 × 10−9 M 6 × 10−8 g mL−1 (2 × 10−7 M) 3 × 10−8 M (morphine)

[56] [206] [141]

Pharmaceutical formulations and spiked serum Synthetic samples

0.006 mg L−1 (2 × 10−8 M)

[40]

FIA. Two analytes detected by measuring CL peak at two flow rates and using simultaneous equations FIA Solid phase extraction followed by FIA FIA

Spiked urine, serum and soil Arabidopsis

Indomethacin

Formaldehyde, polyphosphoric acid

Isoprenaline (isoproterenol) Kaempferol Levodropropizine Levodropropizine ␣-Lipoic acid and dihydrolipoic acid ␣-Lipoic acid

Formaldehyde

FIA

Pharmaceutical formulation and spiked urine (after solid phase extraction) Pharmaceutical formulations

Hydrogen peroxide Formaldehyde, EDTA Formaldehyde Sodium polyphosphate

FIA FIA HPLC (C18 column; isocratic) FIA

Sodium polyphosphate, formaldehyde Formaldehyde Formaldehyde Galangin, polyphosphoric acid Tween-80

FIA and HPLC (C18 column; isocratic) FIA FIA FIA-MIP Molecularly imprinted sol–gel modified microplate

Luteolin Lysozyme Maleic hydrazide Melamine

−7

−1

5.0 × 10 g mL human IgG 6.0 × 10−8 g mL−1 (2 × 10−7 M) thiomersal

[31]

1 × 10−8 M indole-2,3-dione 1 × 10−9 M indole-3-acetic acid 2.8 × 10−9 g mL−1 (2 × 10−8 M)

[47]

−10

6.0 × 10

g mL

−1

−9

(2 × 10

M)

[207] [21]

0.02 ␮g L−1 (1 × 10−10 M)

[208]

Radix Tetrastigme Synthetic samples Serum Not applied

1 × 10−7 g mL−1 (4 × 10−7 M) 3.75 × 10−9 g mL−1 (2 × 10−8 M) 3 × 10−8 g mL−1 (1 × 10−7 M) 3 × 10−7 M 8 × 10−8 M

[209] [210] [211] [56]

Capsules and food products

0.004 ␮g mL−1 (2 × 10−8 M) (FIA) 1.774 ␮g mL−1 (9 × 10−6 M) (HPLC) 3 × 10−8 g mL−1 (1 × 10−7 M) 7.15 ␮g mL−1 2.6 × 10−5 mg mL−1 (2 × 10−7 M) 0.02 ␮g mL−1 (2 × 10−7 M)

[33]

a

Not stated Saliva Spiked vegetables Milk and powdered milk


Glutathione (GSH)

Not stateda Flow analysis system incorporating MIP column as the detection cell FIA

[212] [213] [214] [162]

13

14


Enhancer


Matrix

Limit of detection

Ref.

Melamine

Batch luminometer. Analyte inhibits the CL reaction FIA FIA

Powdered milk

8 pg mL−1 (6 × 10−11 M)

[17]

Pharmaceutical formulations Tablets, spiked serum and urine

25.6 ng mL−1 (7 × 10−8 M) 6 × 10−9 g mL−1 (4 × 10−8 M)

[43] [215]

6-Mercaptopurine

Gold/silver nanoalloys, formaldehyde Formaldehyde Formaldehyde, sodium polyphosphate Sodium hexametaphosphate

Serum

1.9 × 10−11 g mL−1 (1 × 10−10 M)

[25]

Metaraminol

Formaldehyde

7.6 × 10−10 g mL−1 (5 × 10−9 M)

[216]

Metoclopramide

Formaldehyde, sodium dodecyl sulfonate Formaldehyde Formaldehyde

Pharmaceutical formulation and serum Pharmaceutical formulations

31.3 ng mL−1 (1 × 10−7 M)

[46]

Meloxicam 6-Mercaptopurine

Mitomycin Morphine and naloxone

Sodium polyphosphate Sodium polyphosphate

Naphazoline and oxymetazoline

Formaldehyde

1-Naphthylamine Nateglinide Ninhydrin Nitrofurans

Formaldehyde

2-Nitrophenol Paracetamol

Glyoxal Rhodamine B

Phenol Phenolic Citrus aurantium protoalkaloids

Hydrogen peroxide Sodium polyphosphate, Mn(II) or sodium thiosulfate (added to the permanganate reagent)

Formaldehyde

Phenolphthalein

Phenols and polyphenols


Phenols

Sodium polyphosphate, Mn(II)

Phentolamine mesylate

FIA FIA Stopped-flow analysis. Time-resolved detection of the two analytes HPLC HPLC (monolithic C18 column; isocratic) FIA

Spiked meat Secretion of Malpighian tubules of maggots Pharmaceutical formulations

FIA FIA FIA FIA

Waters Not stateda Not stateda Animal feeds

FIA FIA. Analyte inhibits CL reaction of permanganate with calcon and rhodamine B FIA HPLC (monolithic C18 column; isocratic)

Lake water Pharmaceutical formulations

Flow analysis system incorporating MIP column as the detection cell. Analyte inhbits CL reaction of permanganate and ethanol HPLC with UV-abs. and CL detection

Tablets

FIA FIA

Pharmaceutical formulations Binary mixtures

Waste water Weight-loss products

Geographical and vintage classification of some Australian wines Not applied Pharmaceutical formulations and plasma

−9

−1

−9

3 × 10 g mL (9 × 10 M) 0.003 mg L−1 (1 × 10−8 M) morphine 0.003 mg L−1 (9 × 10−9 M) naloxone Not stated Not stated

[44] [60,61]

8.7 × 10−3 mg L−1 (4 × 10−8 M) naphazoline 3.47 × 10−2 mg L−1 (1 × 10−7 M) oxymetazoline 8 × 10−9 M 3.9 × 10−9 g mL−1 (1 × 10−8 M) 3 × 10−8 g mL−1 (2 × 10−7 M) 0.25 mg L−1 (1 × 10−6 M) furazolidone 0.25 mg L−1 (1 × 10−6 M) nitrofurantoin 0.25 mg L−1 (1 × 10−6 M) nitrofurazone 1 × 10−11 M 7 × 10−8 g mL−1 (5 × 10−7 M)

[45,217]

3 × 10−5 g L−1 (3 × 10−7 M) 5 × 10−8 M octopamine 4 × 10−8 M synephrine 7 × 10−8 M tyramine 7 × 10−8 M N-methyltyramine 1 × 10−7 M hordenine 8.9 × 10−9 g mL−1 (2 × 10−7 M)

[222] [28,156]

Not stated

[148,149]

5 × 10−11 M morphine 1 × 10−9 M synephrine 0.82 ␮g L−1 (2 × 10−9 M)

[28]

[143] [144]

[65] [218] [219] [26]

[220] [221]

[127]

[223]


Morphine Morphine

FIA. Analyte inhibits CL reaction of permanganate with thioacetamide FIA

Phentolamine mesylate Picric acid Propyl gallate Puerarin Pyrocatechol Pyrocatechol, resorcinol and hydroquinone Resorcinol, phenol

Resveratrol Resveratrol Retinol derivatives and ␣-tocopherol

Synephrine Tetracycline Thiosemicarbazide Thiourea Thymol Tiopronin Total antioxidant status Total carbonyl compounds

8.0 ␮g L−1 (2 × 10−8 M)

[224]

FIA. Analyte inhibits the CL reaction of permanganate and glyoxal Not stateda FIA FIA HPLC (hypercross-linked polystyrene Chromalite 5HGN column; isocratic) FIA

Dangjiang water samples

1 × 10−12 M

[225]

−6

−1

−8

5.6 × 10 g L (3 × 10 M) 3.0 ng mL−1 (7 × 10−9 M) 1 × 10−8 M Not stated

[226] [39] [227] [32]

Not applied

8 × 10−9 M

[139]

FIA FIA-MIP FIA

Wine Not stateda Pharmaceutical formulations

[228] [229] [24]

Arnebia euchroma Milk and fruit juice Not stateda

3 × 10−7 g L−1 (1 × 10−9 M)

[231]

Glyoxal

FIA-MIP Flow analysis system incorporating MIP column as the detection cell FIA with MIP solid-phase extraction and pre-concentration FIA

Not stateda 8 × 10−6 g mL−1 (3 × 10−5 M) 7 × 10−9 M retinol 7 × 10−9 M retinal 1 × 10−7 M retinoic acid 3 × 10−8 M retinyl acetate 3 × 10−8 M retinyl palmitate 5 × 10−9 M ␣-tocopherol 0.36 ␮g mL−1 (1 × 10−6 M) 2.2 × 10−8 g mL−1 (2 × 10−7 M)

Waste water

2 × 10−9 M

[232]

Glyoxal

FIA


[66]

Not stateda FIA FIA FIA

Fructus aurantii Eggs Water Fruit juice

1 ng mL−1 (9 × 10−9 M) methimazole 6.9 ng mL−1 (3 × 10−8 M) captopril 7.5 ng mL−1 (3 × 10−8 M) cimetidine 0.7 ng mL−1 (5 × 10−9 M) methionine 9 ng mL−1 (3 × 10−8 M) chlorpromazine hydrochloride 1.5 ng mL−1 (5 × 10−9 M) chlorprothixene 3.7 ng mL−1 (2 × 10−8 M) propacil 7 × 10−8 M 0.28 ␮g mL−1 (6 × 10−7 M) 5 × 10−8 M 2 × 10−8 M

FIA Stopped-flow. Time-resolved measurements FIA

Wuji cream Pharmaceutical formulations

4.2 × 10−9 g mL−1 (3 × 10−8 M) 0.12 mg L−1 (7 × 10−7 M)

[237] [62]

Fruit juices and teas

Not stated

[27]

FIA with on-line derivatization with 2,4-dinitrophenylhydrazine

Natural waters and drinking water

[20]

Microfluidic chip incorporating solid-phase microextraction and CL flow cell mounted on a PMT FIA

Green tea

0.14 ␮g L−1 (2 × 10−9 M) acetone 0.17 ␮g L−1 (4 × 10−9 M) acetaldehyde 0.17 ␮g L−1 (6 × 10−9 M) formaldehyde 1 × 10−9 M

Teas

2 × 10−9 g mL−1

[238]

Formaldehyde, sulfuric acid

Formaldehyde A sulfonophenylazo rhodanine derivative

Formaldehyde Glyoxal Cetyltrimethylammonium bromide (CMTAB) Rhodamine 6G Formaldehyde Sodium polyphosphate

Total catechins


[230] [161]

[233] [234] [235] [236]

[150]

15

Total polyphenols


Edible blended oils Pharmaceuticals and spiked urine Natural waters Not applied

Formaldehyde, fluorescein Glyoxal Galangin, polyphosphoric acid Sodium polyphosphate, sodium thiosulfate (added to the permanganate solution) Sodium polyphosphate, sodium thiosulfate (added to the permanganate solution) Formaldehyde, fluorescein

Sudan I 5-Sulfosalicylic acid Sulfur compounds

FIA


Shikonin Sorbic acid

Fluorescein and polyethylene glycol-200

[241] [242] Not stateda 5 × 10−8 M Urine Blood SIA incorporating on-line dilution Not stateda Uric acid Vincristine

a Paper in language other than English, and the relevant information was not available in English language abstract. Abbreviations: BSA: bovine serum albumin; CL: chemiluminescence; DPPH: 2,2-diphenyl-1-picrylhydrazyl; EDTA: ethylenediaminetetraacetic acid; FIA: flow injection analysis; HSA: human serum albumin; HPLC: high performance liquid chromatography; IC: ion chromatography; MIP: molecular imprinted polymer; PMT: photomultiplier tube; SIA: sequential injection analysis.

[56] 4 × 10−9 M Not applied l-Tyrosine

Sodium polyphosphate, sodium thiosulfate (added to the permanganate solution) Formaldehyde Rhodamine 6G

[15] [239] [58,240] [57] Cattle feeds Not stateda Amino acid mixture Pharmaceutical formulations

FIA FIA-MIP FIA FIA-MIP (in sample line, prior to detection flow-cell) FIA Trenbolone acetate Trichlorfon Tryptophan l-Tryptophan

Galangin, polyphosphoric acid Tin(II) chloride, formic acid

[14]

0.005 ␮g mL−1 (1 × 10−8 M) berberine 0.004 ␮g mL−1 (1 × 10−8 M) palmatine 0.0007 ␮g mL−1 (2 × 10−9 M) jatrorrhizine 0.05 mg L−1 (2 × 10−7 M) 2.8 × 10−8 g mL−1 (1 × 10−7 M) 5 × 10−3 ␮g mL−1 (2 × 10−8 M) 2 × 10−8 M Ethanol extracts of medicinal plants Total protoberberine alkaloids

Analyte

Table 1 (Continued)

Enhancer

Alizarin yellow R

Ref. Limit of detection Matrix

Batch luminometer. Standard addition method. Interfering compounds (e.g. flavanoids) removed with aluminium oxide column



16

Fig. 1. Chemiluminescent reaction of potassium permanganate (in acidic solution containing sodium polyphosphates) with morphine. The photograph was taken as one reactant solution was poured into a flask containing the other solution.

solution (which do not lead to the characteristic red emission often observed under acidic conditions) and the permanganate oxidation of tris(2,2 -bipyridyl)ruthenium(II) in acidic solution [10–12], where subsequent reduction with a suitable analyte evokes the characteristic emission from the ruthenium(II) complex [13]. We have, however, included discussion on the chemiluminescent reactions of permanganate with sulfite and various other reductants in acidic solution for which a range of alternative emitting species have been reported. 2. New insights into acidic potassium permanganate chemiluminescence 2.1. The characteristic red emission Many researchers have visually observed a red emission from reactions with potassium permanganate in acidic solution (Fig. 1) or obtained a chemiluminescence spectrum comprising a single broadly distributed band with an apparent maximum intensity between 550 nm and 750 nm (e.g. [14–17]). The variation in reported values can be largely attributed to differences in instrumental sensitivity across that wavelength range. Correction for this instrumental artefact has revealed a maximum emission at 734 ± 5 nm (or 689 ± 5 nm if polyphosphates are used as an enhancer) [18]. The red emission from these reactions has often been assumed to be ‘singlet’ molecular oxygen (discussed below), but there is now overwhelming evidence to show that it in fact emanates from an electronically excited Mn(II) species [18,19]. This evidence includes: (i) the spectral distribution of the characteristic red emission is independent of the analyte [18], (ii) Mn(II) is the final reduction product of permanganate in acidic solution; (iii) the chemiluminescence has the same spectral distribution as the laser-induced phosphorescence (4 T1 →6 A1 transition) of MnCl2 in aqueous solution at room temperature [19]; (iv) the same spectrum is also observed for the chemiluminescent reduction of Mn(IV) and Mn(III) in acidic aqueous solution with a variety of analytes [18]. Although alternative emitters continue to be postulated, an


17

be ascribed to singlet oxygen unless the spectral distribution is matched to confirm its presence. 2.3. Polyphosphate The chemiluminescence from many reactions with permanganate has been significantly enhanced by adding sodium polyphosphate (0.05–1%, m/v) and adjusting the pH to between 2 and 4 with sulfuric or orthophosphoric acid [9]. A series of investigations have revealed a mechanism of enhancement involving the stabilization of Mn(III) (precluding the flocculation of insoluble Mn(IV)) and the formation of protective ‘cage-like’ structures around the Mn(II)* emitter, which shift the wavelength of maximum emission from 734 ± 5 nm to 689 ± 5 nm and inhibit non-radiative relaxation pathways [50]. As previously noted [9], more acidic conditions are generally required to obtain the greatest intensity in applications of permanganate chemiluminescence in which polyphosphate is not used. Considering the well-established chemistry of manganese in solution [51,52], this can be ascribed to the stabilization of Mn(III) and prevention of extensive aggregation of Mn(IV). 2.4. Generalized reaction mechanism Scheme 1. Generalized light-producing pathway of permanganate chemiluminescence [32]: (a) multistep reduction of permanganate with analyte-dependent rate of reaction; (b) Mn(III) intermediate stabilized by complexing agents such as polyphosphate [50] or under highly acidic conditions; (c) radicals derived from the analyte react with Mn(III) to form the Mn(II)* emitter [50]; (d) radiative decay to the ground state product [19]; (e) reaction of permanganate with reducing agents, either during preparation (e.g. thiosulfate), or merged with the reagent on-line (e.g. formic acid or formaldehyde) to form a greater pool of Mn(III), which can enhance the chemiluminescence signal from the analyte [29,32]; and (f) deleterious reaction of reducing agent with Mn(III). Reprinted from Analytica Chimica Acta, 707, T. Slezak, Z.M. Smith, J.L. Adcock, C.M. Hindson, N.W. Barnett, P.N. Nesterenko, P.S. Francis, Kinetics and selectivity of permanganate chemiluminescence: A study of hydroxyl and amino disubstituted benzene positional isomers, 121–127, Copyright (2011), with permission from Elsevier.

electronically excited Mn(II) species is now commonly recognized as the emitter in chemiluminescent reactions with acidic potassium permanganate [14,17,20–36]. 2.2. Singlet oxygen Electronically excited ‘singlet oxygen’ (1 O2 ) species are thought to be generated in many chemiluminescence systems [37,38], the most well-known of which is the reaction of hydrogen peroxide and sodium hypochlorite. The principle emission bands of 1 O2 occur in the near-infrared (max = 1270 nm) from a monomeric species ((0,0), 1 g →3 g − ;) and in the visible region (max = 703 nm and 633 nm) from its dimeric aggregate ((1 g )=0 (1 g )=0 → (3 g − )=1 (3 g − )=0 and (1 g )=0 (1 g )=0 →(3 g − )=0 (3 g − )=0 ) [37,38]. Numerous researchers have attributed the characteristic red emission from reactions with permanganate in acidic solution to the generation of singlet oxygen [15,16,39–49], but the evidence against this is compelling: (i) the spectral distribution in the visible region is different [18]; (ii) attempts to detect the unimolecular emission in the near-infrared have been unsuccessful [18] (although it can be detected during the reaction of hydrogen peroxide and hypochlorite [37]); (iii) the reactions are not significantly affected by the concentration of dissolved oxygen or singlet oxygen quenchers (sodium azide and histidine) [18,25]; and (iv) there is now unequivocal evidence that the characteristic red emission emanates from a Mn(II)* species (see above). Observations of a red emission (with a maximum intensity within the range 600–750 nm) from reactions with permanganate should no longer

The intense red emission from reactions with acidic potassium permanganate can also be observed from reactions of Mn(III) with powerful reducing agents [18]. It is thus reasonable to suggest that single electron transfer to the Mn(III) intermediate of permanganate reactions (discussed above) occurs from reactive radical intermediates formed in the initial reaction of the analyte with permanganate [50]. The identification of such radical intermediates under typical analytical conditions using electron paramagnetic resonance (EPR) spectroscopy [50] and the enhancing effect of initial high concentrations of Mn(III) in the permanganate reagent (as described in the following section) has provided considerable support for this generalized reaction scheme (Scheme 1a–c). An understanding of the structural requirements of analytes that elicit an intense chemiluminescence emission with permanganate has been approached from two perspectives. Firstly, the large number of papers on the determination of specific compounds and comparisons of groups of related compounds has provided considerable empirical evidence [9]. Secondly, Martínez Calatayud and co-workers have explored the use of molecular connectivity calculations to predict the responsiveness of various compounds to this mode of detection [53,54]. At present, neither approach has provided a definitive explanation of the relationship between the chemical structure of the analyte and chemiluminescence intensity. It is well established that acidic potassium permanganate is effective for the detection of many readily oxidizable phenols, anilines and related compounds, but subtle changes in structure can have a dramatic effect on the chemiluminescence intensity, and as shown in Tables 1 and 2, permanganate has been used to detect many other compounds. A detailed discussion of the relationship between analyte structure and permanganate chemiluminescence intensity was featured in our previous review [9]. 2.5. Preliminary partial reduction of the reagent In 1991, Tsaplev described an experiment in which he added ethanol to permanganate in acidic solution to slowly reduce the oxidant to Mn(II) [55]. He repeatedly measured the chemiluminescence generated by this reagent with morphine and observed a transient six-fold increase in emission intensity that peaked at 25 min. The author concluded that the formation of Mn(II) inhibited a direct non-radiative reaction in favour of a light-producing pathway via Mn(III) [55]. In a related experiment conducted in

18


2010, Slezak and co-workers added Mn(II) to an acidic potassium permanganate solution containing sodium polyphosphate and periodically measured the emission from the reaction with morphine using flow injection analysis (FIA) methodology, which increased by 5.5-fold over 24 h, and then gave a near identical response for the next 48 h [28]. Spectrophotometric and stoppedflow chemiluminescence experiments revealed that the increase in intensity was the result of a greater concentration of Mn(III) in the permanganate reagent (Scheme 1d), which increased the rate of the light-producing reaction with morphine and various other phenolic compounds [28]. A much faster approach to prepare this enhanced reagent was developed, using sodium thiosulfate to perform an immediate partial reduction of the oxidant [29]. It should be noted that when permanganate is reduced by Mn(II), only a fifth of the Mn(III) product is derived from the oxidant, but when thiosulfate is used, the oxidant is the only source of Mn(III) and therefore greater initial concentrations of permanganate may be required. This reagent has been found to be particularly effective for compounds that otherwise react relatively slowly with permanganate, such as phenols without additional hydroxyl, alkoxyl or similar groups in ortho or para positions (e.g. synephrine, tyrosine, resorcinol and fenoterol), for which enhancement in emission intensities of up to twoorders of magnitude have been observed [28,29,32,56]. Some other reported enhancers of permanganate chemiluminescence may act by rapidly reducing the reagent to intermediate manganese species (Scheme 1e). For example, Qui et al. reported the addition of 1 mM Sn(II) significantly enhanced the emission from the reaction of permanganate, tryptophan and formaldehyde [57]. Similarly, Chen and co-workers reported considerable enhancement from the addition of the flavanol galangin in their determination of tryptophan [58] and human IgG and thiomersal [31] with permanganate and polyphosphoric acid. 2.6. Formaldehyde and related enhancers Several low molecular weight aldehydes and related compounds have continued to be employed as enhancers of permanganate chemiluminescence. By far the most commonly used is formaldehyde [16,21,24,33,40–47,57,59–65], but formic acid [49,57], glyoxal [39,48,66] and glutaraldehyde [22,67] enhancers can also be found in recent publications. These enhancers are generally merged with the reactant solutions on-line, shortly prior to the point of detection, because the enhancer also directly reacts with the oxidant (which is observed as a constant background emission). The mechanism of the reactions that produce the background chemiluminescence signal and the enhanced analyte response are yet to be fully elucidated, but similar to publications described in our prior review [9], numerous researchers have postulated that these species are oxidized to form excited carbon dioxide [21] or singlet oxygen [39–44,46]. Some support for an alternative emitter was obtained by Fu and Wang [21], who obtained a chemiluminescence spectrum (using interference filters) for the reaction of permanganate, formaldehyde and indomethacin showing emission maxima at both 490 nm and 610 nm, although the experimental error for each point appeared to be relatively high. A similar spectral distribution was reported by Wabaidur et al. for the reaction of permanganate, dopamine and formaldehyde [63]. Wang et al. found two maxima in the chemiluminescence spectrum for the reaction of permanganate, naphazoline and formaldehyde (in a similar wavelength region to those of singlet oxygen) [45]. Yet another light-producing pathway, involving energy transfer from Mn(II)* to a formaldehyde emitter, was recently raised by Wolyniec and co-workers [33]. However, the experimental evidence for a Mn(II) emitter from numerous closely related reactions with permanganate [18,19] and the identical spectral distribution

for several reactions in the presence and absence of formaldehyde [16,33,41,47] or glyoxal [39] do not support these as general explanations for the action of formaldehyde and related enhancers. Other researchers have suggested that these enhancer species increase the rate of reaction [42–44,46,49]. Spectrophotometric monitoring of the reactions under analytically relevant conditions has indicated that the enhancement from formaldehyde and formic acid can indeed be in part attributed to the generation of greater concentrations of the key Mn(III) precursor to the Mn(II)* emitting species (Scheme 1e) [24,32]. 2.7. Fluorescent compounds Fluorescent compounds (e.g. rhodamine B, rhodamine 6G, quinine and fluorescein) have been tested as potential enhancers of permanganate chemiluminescence reactions on many occasions, but have only been found to be of benefit in a few cases [9]. Some researchers have proposed light-producing pathways involving energy transfer to an added fluorophore, or the formation of a fluorescent product derived from the analyte, although a direct comparison of the chemiluminescence emission spectrum with the characteristic photoluminescence of the proposed emitter has rarely been provided. In 2009, we re-examined sixteen previously published permanganate chemiluminescence systems in which fluorescent compounds were present, either added as enhancers or formed by oxidation of the analyte [68], and found that in almost all cases, the broad red band (attributable to Mn(II)* [19]) was the only observable emission. There were, however, some notable exceptions [68], including the oxidations of dihydralazine [69], sulfite [70] and thiol compounds [71] that produced intermediates capable of energy transfer to efficient fluorophores (rhodamine B, riboflavin and quinine, respectively). In these cases, the high energy intermediates are derived from the analyte, and can be generated using alternative oxidants such as Ce(IV). Nevertheless, when permanganate is employed, the concurrent generation of Mn(II)* can make a significant contribution to the overall chemiluminescence emission [68]. 2.8. The oxidation of sulfite with and without enhancers In 1975, Stauff and Jaeschke reported that the oxidation of sulfite by permanganate (or various other oxidants) is accompanied by a weak emission of light [3]. They subsequently showed that the emission was distributed between 450 and 600 nm, and proposed a light-producing pathway involving the formation of an unstable, asymmetric intermediate (HO3 S–O–SO2 H) from two hydrogen sulfite radicals, which breaks down to produce sulfur dioxide in an electronically excited state (Scheme 2) [72,73]. This mechanism is often recounted in the literature as fact rather than postulation and often without showing the asymmetry of the proposed key intermediate [74–78]. Considerable increases in emission intensity have been obtained by the inclusion of certain highly fluorescent species (such as riboflavin [70] and Al(III)-tetracycline complexes [79]) or non-fluorescent compounds (such as 3-cyclohexylaminopropanesulfonic acid (CAPS) [70] and carbofuran [80]) to the reaction mixture [81], which has been exploited for a variety of analytical applications (see Table 3 and Ref. [9]). In the case of fluorescent compounds, energy transfer from the excited sulfur dioxide to the efficient fluorophore is generally assumed [70,79,82]. Chemiluminescence matching the characteristic fluorescence from the sensitizer has been observed, but there are other examples where the spectral distribution is different, which may result from oxidation of the sensitizer prior to energy transfer and emission [81].


19

Table 2 Determination of inorganic compounds with acidic potassium permanganate chemiluminescence. For older applications, see Table 2 in reference [9]. Analyte

Enhancer/ Co-reagent


Matrix

Limit of detection

Ref.

Aluminium Aluminum l-lactate Arsenic(III)

Not stateda FIA FIA

Water Wastewaters Water samples

8 × 10−9 M 1 × 10−6 g mL−1 (3 × 10−6 M) 0.001 ␮g mL−1 (1 × 10−8 M)

[243] [244] [245]

Copper(II)

Calcein Gold nanoparticles Sodium hexametaphosphate, formaldehyde Morin

Not stateda

0.0012 ␮g mL−1 (2 × 10−8 M)

[246]

Iodide Nitrite

Pyronine B Glyoxal

Environmental waters Foods and water

1.6 × 10−4 ␮g mL−1 (1 × 10−9 M) 1 × 10−9 M

[247] [248]

Sulfide Sulfite Sulfite

CAPS

Spiked seawater Beer Food

2 × 10−7 M Not stateda 0.2 mg L−1 (2 × 10−6 M)

[94] [249] [163]

Sulfur dioxide

Resorcin

FIA with on-line separation and enrichment by ion imprinted polymer FIA FIA. Analyte inhibits CL reaction FIA FIA FIA incorporating on-line conversion to sulfur dioxide and separation by pervaporation FIA. Analyte inhibits CL reaction FIA. On-line reduction with amalgamated zinc column

Food

0.03 mg L−1 (5 × 10−7 M)

[250]

Rhodamine B, sodium hexametaphosphate

Vanadium(III)

Formaldehyde

Seawater (certified reference materials)

−10

8 × 10

M

[172]

a Paper in language other than English, and the relevant information was not available in English language abstract. Abbreviations: CAPS: N-cyclohexyl-3-aminopropanesulfonic acid; CL: chemiluminescence; FIA: flow injection analysis.

CAPS was found to provide even better limits of detection for sulfite than when using fluorescent enhancers such as quinine or riboflavin [70,82] and the enhancing effect of this non-fluorescent molecule was postulated to involve the formation of a ␤-sultine [73]. The oxidation of sulfite with permanganate (or Ce(IV)) enhanced by CAPS produces a broad emission (350–650 nm) with a maximum intensity at 458 nm (477 nm after correction) [81]. Other weakly fluorescent or non-fluorescent enhancers (such as papaverine [75], colistin [83], tramadol [78], ibuprofen [84–86] and loxoprofen [77]) have subsequently been identified. It has been proposed by some researchers that these enhancers may simply increase production of SO2 * [75,77,78,87–89], but a single common emitter in all cases is unlikely as several different spectral distributions have been recorded [75,78,81,87,89,90]. Kanwal and co-workers [76] recently described the sensitive determination of ethylenediaminetetraacetate (EDTA) based on its inhibition of the

Ce4+ + HSO3- → HSO3• + Ce3+

(1a)

MnO4- + HSO3- → HSO3• + MnO42-

(1b)

HSO3• + Ox + H2O → H2SO4 + Ox- + H+

(2)

•

•

HO3S + SO3H → HO3S-SO3H •

(3a)

•

HO2SO + OSO2H → HO2SO-OSO2H

(3b)

HO3S• + •OSO2H → HO3S-O-SO2H

(3c)

(HS2O6)- → SO3 + HSO3-

(4)

(HS2O6) → SO2 + SO4 + H -

*

*

SO2 +H2O + Ox → SO2* → SO2 + hν ν

2-

HSO3•

+

(5) -

+ Ox + H

+

(6) (7)

Scheme 2. The mechanism of the chemiluminescent oxidation of sulfite as proposed by Stauff and Jaeschke [72], with the light producing pathway using cerium(IV) or permanganate shown in bold.

chemiluminescent reaction of permanganate, sodium sulfite and hydrogen peroxide. The emission, ascribed to SO2 * , was found to predominantly occur between 500 and 600 nm (both with and without the presence of EDTA) [76]. A variety of oxidants can be used to elicit chemiluminescence with sulfite, but when permanganate is employed, there can be two concurrent light-producing pathways: the oxidation of sulfite to form an excited intermediate (possibly SO2 * ) and the reduction of permanganate to form Mn(II)* , with their relative contributions highly dependent on reaction conditions. Unlike Mn(II)* , the sulfite oxidation products readily transfer energy to common sensitizers, and the light-producing pathway is not as dependent upon acidic conditions. Although rarely considered in papers on the chemiluminescence reaction of permanganate and sulfite, the generation of Mn(II)* can make a significant contribution to the overall emission [81], but this can be masked by the poorer sensitivity of commonly used photodetectors at the red end of the spectrum. Similar to other permanganate reactions, the addition of sodium polyphosphates can increase the contribution from the Mn(II)* emitter (max = 689 nm) by over two-orders of magnitude [81]. 2.9. Other sulfur compounds Although less thoroughly investigated, the oxidation of various other sulfur oxyanions and thiol compounds can generate species capable of emission or energy transfer to sensitizers such as rhodamine dyes and quinine [71,81,91–93], which may involve similar light-producing pathways to the oxidation of sulfite. Adding weight to this notion is the finding that non-fluorescent enhancers such as CAPS also increase the emission from the oxidation of thiols [81] and sulfide [94], and produced the same spectral distribution, after removal of the contribution from the unenhanced oxidation of the thiol [81]. Without the presence of enhancers, the chemiluminescence spectra for the oxidation of captopril with permanganate in acidic solution produced a single band with a maximum at 410 ± 5 nm [81]. A comparison of the overall emission intensity for this reaction in the presence of quinine or CAPS using FIA methodology revealed that the effectiveness of the enhancer was in part

20


Table 3 Determination of compounds that enhance of the chemiluminescence from potassium permanganate and sulfite or related species. For older applications, see Table 3 in reference [9]. Analyte

Sulfur species


Matrix

Limit of detection

Ref.

Atenolol

Sodium sulfite, Eu3+

FIA

Sodium sulfite

FIA

Chlortetracycline Cinchona alkaloids

Sodium sulfite Sodium hydrosulfite, polyphosphoric acid

FIA FIA

Colistin (Polymyxin E)

Sodium sulfite

FIA

3 × 10−9 g mL−1 (1 × 10−8 M) 2 × 10−10 g mL−1 (8 × 10−10 M) 1 × 10−8 M 3.2 × 10−8 g mL−1 (1 × 10−7 M) quinine 3.0 × 10−8 g mL−1 (9 × 10−8 M) quinidine 3.0 × 10−8 g mL−1 (1 × 10−7 M) cinchonine 1 × 10−6 M

[96]

Carbamazepine

Spiked urine and plasma Pharmaceutical formulations Not stateda Pharmaceutical formulations, serum and urine

Dextromethorphan

Sodium sulfite

FIA

Enoxacin

Sodium thiosulfate, Dy3+

FIA

Enrofloxacin

Sodium thiosulfate

FIA

Ethylenediaminetetraacetic acid (EDTA)

Sodium sulfite, hydrogen peroxide

Fleroxacin

Furosemide

Sodium thiosulfate, Dy3+ , polyphosphoric acid Sodium hydrosulfite

FIA. Analyte inhibits CL reaction (KMnO4 solution adjusted to pH 8.5) FIA

Hydrocortisone

Sodium sulfite

FIA

Ibuprofen

Sodium sulfite

Ibuprofen

Sodium sulfite

FIA after 3-phase hollow fiber-based liquid-phase microextraction (for urine) FIA with ultrafiltration

Levonorgestrel

Sodium sulfite

FIA

FIA

Pharmaceutical formulations Nasal drops

−1

[252] [93]

[83]

3.5 × 10 g L (1 × 10−8 M) 0.22 ng mL−1 (7 × 10−10 M)

[253]

1.1 × 10−7 g mL−1 (3 × 10−7 M) 4 × 10−13 M

[254]

Pharmaceutical formulations and urine

3 × 10−10 g mL−1 (8 × 10−10 M)

[99,101]

Pharmaceutical formulations Pharmaceutical formulations Pharmaceutical formulations and urine

5.7 ␮g L−1 (2 × 10−8 M)

[255]

4 × 10−10 g mL−1 (1 × 10−9 M) 0.03 ␮g mL−1 (1 × 10−7 M)

[256]

10 ␮g L−1 (5 × 10−8 M)

[86]

6.4 ␮g L−1 (2 × 10−8 M)

[257]

Pharmaceutical formulations and spiked serum and urine Veterinary formulations Canned foods

Plasma (pharmacokinetic study) Pharmaceutical formulations Pharmaceutical formulations Pharmaceutical formulations and spiked biological fluids Plasma and urine

Meloxicam

Sodium sulfite

FIA

2-Methoxyestradiol

Sodium sulfite

FIA

Metoprolol tartrate

Sodium sulfite, Eu3+

FIA

Naproxen and loxoprofen

Sodium sulfite

FIA


Nonsteroidal anti-inflammatory drugs

Sodium sulfite

HPLC (C18 column; gradient elution)

Spiked plasma

Norfloxacin

Sodium sulfite, Tb3+

Pharmaceutical formulations and spiked serum

Norfloxacin

Sodium thiosulfate

Flow analysis system with permanganate immobilized on anionic exchange resin in a glass tube flow cell FIA

Prulifloxacin

Sodium thiosulfate, Tb3+

Batch luminometer

−6

[251]

Pharmaceutical formulations Pharmaceutical formulation and spiked serum and urine

−8

5 × 10

[98]

[76]

[85]

M

[258]

8 × 10−9 M

[259]

1 × 10−7 g mL−1 (4 × 10−7 M) 2 × 10−8 g mL−1 (9 × 10−8 M) 3 × 10−8 g mL−1 (1 × 10−7 M) 0.5 ng mL−1 (2 × 10−9 M) ibuprofen 0.05 ng mL−1 (2 × 10−10 M) naproxen 0.5 ng mL−1 (2 × 10−9 M) fenbufen 9 × 10−9 M

[260]

8.4 × 10−9 g mL−1 (3 × 10−8 M) 8 × 10−9 M

[261]

[77]

[84]

[97]

[100]


21


Sulfur species


Matrix

Quinolone antibiotics

Sodium thiosulfate, Dy3+

FIA

Not applied.

Rifampicin

Sodium sulfite

FIA

Sulpiride

Sodium sulfite

FIA

Tetracyclines

Sodium sulfite

Tramadol

Sodium sulfite

Batch luminometer and FIA. Chemiexcitation of the fluorescent Al(III) tetracycline complex FIA

Pharmaceutical formulations Pharmaceutical formulations Pharmaceutical formulations


Limit of detection −10

−1

Ref.

2.2 × 10 g mL (7 × 10−10 M) enoxacin −10 g mL−1 3.0 × 10 (8 × 10−10 M) fleroxacin 6.0 × 10−10 g mL−1 (2 × 10−9 M) pefloxacin 2.2 × 10−10 g mL−1 (7 × 10−10 M) pipemidic acid 3 × 10−8 g mL−1 (4 × 10−8 M) 3 × 10−8 g mL−1 (9 × 10−8 M) Limits of detection using Ce(IV) as the oxidant stated.

[102]

0.01 ␮g mL−1 (4 × 10−8 M)

[78,264]

[262] [263] [79]

a Paper in language other than English, and the relevant information was not available in English language abstract. Abbreviations: CL: chemiluminescence; FIA: flow injection analysis; HPLC: high performance liquid chromatography.

dependent on the oxidant. When permanganate was used, the signal from captopril was enhanced by 50% with CAPS and 700% with quinine, but when cerium(IV) was used, the signal was enhanced by 450% with CAPS and was decreased by 52% with quinine [81]. Again, the contribution of the two possible light producing pathways to the overall emission is determined by reaction conditions. For example, Li and co-workers reported the determination of glutathione and other thiol compounds based on the chemiluminescence reaction with permanganate enhanced by quinine [71], where the emission matched the characteristic blue light of the added fluorophore [81]. However, McDermott et al. and Terry et al. replaced the quinine with sodium polyphosphate, which promoted the emission of red light from the Mn(II)* emitter [56,95]. Similarly, the dominant emitter in the reaction of sulfite and permanganate (in sulfuric acid) enhanced by quinine was that of the added fluorophore [81], but for the reaction of permanganate, thiosulfate and quinine in a polyphosphoric acid medium, a distinct red emission was observed [93]. The authors of that study postulated a singlet oxygen emitter, but as discussed above, there is overwhelming evidence that the characteristic red emission from permanganate reactions results from the formation of Mn(II)* . Wang et al. detected a red emission from the reaction of permanganate and thioacetamide in the presence of sodium polyphosphate [25], which they ascribed to Mn(II)* . Interestingly, the reaction was found to be inhibited by another thiol, 6-mercaptopurine [25]. Other sulfur compounds reported to undergo chemiluminescent reactions with permanganate include thiones, thioethers and disulfides [25,56,66]. 2.10. Lanthanide complexes The weak emission of light from the reaction of sulfur oxyanions with permanganate (and with other oxidants) has also been enhanced by complexes of lanthanide ions with organic ligands [96–102], and this class of enhancer warrants further explanation. The luminescence of lanthanide ions arises from formally Laporte-forbidden electronic transitions within their 4fn configuration [103,104]. These electrons are shielded by the filled 5s and 5p shells, and therefore the spectral distributions of the sharpline emissions of lanthanide species are largely independent of the surrounding matrix (although their relative intensities can vary greatly). The light absorption bands of the lanthanide ions are narrow and very weak, but their complexation with various organic

ligands induces much brighter photoluminescence, via more efficient excitation of the ligand chromophore, followed by energy transfer to the protected metal center, from which the characteristic emissions occur. The photoluminescence of lanthanides is longer lived than that of organic fluorophores, which enables timeresolved measurements [103,104]. Lanthanide complexes can also be excited by energy transfer from an intermediate produced in the oxidation of sulfite or thiosulfate, leading to emissions from the metal center as observed in photoluminescence studies [90]. Following on from papers included in our previous review [105–107], this approach has mostly been applied to fluoroquinolones [97–102], which can act as effective sensitizing chromophores for europium(III) [106], terbium(III) [97,100,105,107] or dysprosium(III) [98,99,101,102] ions. For europium(III), the commonly observed emission maxima occur at 580, 590, 613, 650, 690 and 710 nm (5 D0 →7 FJ , where J = 0–5 [103,106]); for terbium(III), at 490, 545 (most intense), 590, and 620 nm (5 D4 →7 FJ , where J = 6–3 [90,103]); and for dysprosium(III), at 482 and 578 nm (4 F9 →6 HJ , where J = 15/2 and 13/2 [98]). Li and co-workers reported the determination of the ␤-blocker atenolol as a sensitizing ligand of europium(III) [96]. In line with the preceding discussions, they found that the atenolol-europium(III) complex enhanced the weak chemiluminescence from reactions of permanganate with sulfite or thiosulfate, but not from permanganate with formaldehyde, formic acid or hydrogen peroxide. 2.11. Nanoparticles and related materials Over the past few years, nanoparticles have been used to enhance the emission intensity or extend the analytical applications of many chemiluminescence detection systems [108–110], including acidic potassium permanganate [17,34,35,111–114]. Shortly before our previous review [9], Zhang and co-workers reported their observations of an emission of red light from the reaction of acidic potassium permanganate with gold nanoparticles [35]. The most intense response was obtained from the smallest particles (2.6 nm), which the authors attributed to their higher reducing ability and faster rate of reaction with the permanganate reagent to form Mn(II)* . More recently, Manzoori et al. used gold-silver alloy nanoparticles (∼10 nm) to enhance the chemiluminescent reaction of permanganate and formaldehyde in the presence of sodium dodecyl sulfate [17]. They remarked that the particles could facilitate the oxidative cleavage of a permanganate

22


ester intermediate, accelerating the generation of Mn(III), which as discussed in Sections 2.4 and 2.5, provides greater emission intensities. The system was applied to the determination of melamine based on its inhibiting effect on the chemiluminescence (ascribed to binding with the nanoalloy) [17]. Hassanzadeh and co-workers used gold nanorods to enhance the emission from the reaction of permanganate and rhodamine B [111]. The reaction was applied to the determination of albumin, again based on the binding between analyte and particle, which inhibited the chemiluminescence. The emission spectrum showed a maximum at 580 nm, which the authors ascribed to the luminescence of rhodamine B in acidic solution, but without correction for the wavelength dependence of the detector sensitivity, a Mn(II)* emitter cannot be dismissed. In a related study, Iranifam and co-workers reported that selenium nanoparticles increased the rate and chemiluminescence intensity of the reaction of permanganate with dinitrobutylphenol [34]. Spectroscopic evidence ruled out the direct reaction of oxidant and nanoparticle, and the authors proposed that the light producing reaction was catalyzed by the particle surface, which accelerated the generation of Mn(III) and Mn(II)* . Cadmium telluride quantum dots have been used in chemiluminescence reactions of permanganate and deltamethrin [112], ascorbic acid [113] or estrogens [114] in acidic or near-neutral solutions. In each case the red emission was attributed to the quantum dots (via the 1Se–1Sh exciton), with researchers noting the similar spectral distribution of the chemiluminescence and photoluminescence [112–114]. This is certainly plausible; CdTe quantum dots have been used as the luminophore in the chemiluminescence reaction of cerium(IV) and sulfite [115]. However, there is some evidence that Mn(II)* may also contribute to the emission (although not considered in these studies [112–114]): several of the analytes or closely related compounds have previously been determined by direct reaction with permanganate [9]; the quantum dots were capped with thiol compounds, including glutathione, which have also previously been determined by permanganate chemiluminescence [95]; and in two studies [113,114] the chemiluminescence was found to be significantly enhanced by the addition of sodium polyphosphate (see Sections 2.3 and 2.8). Wang and co-workers used carbon-dots on nanoporous gold as a signal amplification label for a DNA biosensor constructed on a microfluidic paper-based device [116]. After the hybridization reactions, the chemiluminescence was initiated by adding a solution of permanganate. Although the reaction was not performed under acidic conditions, it was proposed that the measured emission arose from both the excitation of the carbon-dots and the reduction of permanganate to Mn(II)* . However, the chemiluminescence spectrum was not examined [116]. Graphene oxide coated with magnetic Fe3 O4 nanoparticles was used by Qiu and co-workers in an effective approach to immobilize a molecular imprinted polymer within a FIA system for the selective chemiluminescence detection of l-tryptophan with permanganate, tin(II) and formaldehyde [57]. In this system, the nanoparticle materials were not involved in the light-producing chemical reaction.

3. Analytical applications 3.1. Pharmaceutical and clinical Numerous papers describing the determination of pharmaceuticals using acidic potassium permanganate chemiluminescence have been published (see Tables 1 and 3). In relatively simple samples, such as commercial pharmaceutical formulations, the permanganate reagent is often sufficiently selective for quantitation using flow-analysis methodology (e.g. FIA, SIA, multicommutation)

without physical separation of the analyte from other sample constituents [16,21,23,24,39–41,43–46,49,62,63,66,117,118]. This approach has also been applied to the determination of pharmaceuticals and biomolecules in urine [21,39,47,48,63,118] and/or serum [25,40,41,47]. However, numerous studies have shown that there are native compounds in these biological samples that elicit light with acidic potassium permanganate [7,64,118–121], and the sheer number of pharmaceuticals that can be determined with this reagent (see Table 1 and Ref. [9]) indicates the high risk of interference from other medications possibly present in urine or serum. Published applications of flow analysis methodology without separation procedures to biological samples are therefore normally limited to percentage recoveries in spiked samples. Nevertheless, when surveyed as a group, these studies provide useful information on the scope of permanganate chemiluminescence detection. Similar general conclusions can be drawn for procedures involving the reaction of permanganate with sulfite or other sulfur oxyanions and various enhancers (Table 3). For example, Payán and co-workers found that ibuprofen significantly enhanced the chemiluminescent reaction of permanganate and sulfite, but this enhancing effect could not be directly applied to the determination of ibuprofen in urine using FIA because of the high blank signal from other compounds present in the sample [85]. However, after hollow fiberbased liquid-phase microextraction of the analyte from the matrix, the FIA procedure gave similar results to that of HPLC for a series of urine samples from a subject administered with a 600 mg dose. To impart greater selectivity for the determination of one or more specific analytes in complex biological sample matrices, acidic potassium permanganate chemiluminescence detection has been successfully combined with separation techniques such as high performance liquid chromatography [95,122,123], ion chromatography [64], capillary electrophoresis [124–126] and molecular imprinted polymer (MIP) materials [57,121,127,128]. Since the publication of our previous review [9], Wan and co-workers have described a molecular recognition chemiluminescence sensor for the determination of amoxicillin in urine [121]. Using FIA methodology, samples were pumped through a MIP column, onto which the analyte was adsorbed; the matrix was washed out of the column; and then the acidic permanganate reagent was pumped into the column to produce the chemiluminescence signal. The MIP approach improved the tolerable ratio of interfering species (including various amino acids, metal ions and pharmaceuticals) generally by 1–2 orders of magnitude compared to conventional FIA. The results for urine samples from three individuals that had consumed amoxicillin capsules were in good agreement with a HPLC method [121]. Xiong and co-workers described the determination of three non-steroidal anti-inflammatory drugs (ibuprofen, naproxen and fenbufen) in plasma based on a reversed-phase HPLC separation (12 min) and chemiluminescence detection with sulfite and permanganate [84]. An examination of mobile phase additives revealed that phosphoric acid was more compatible with this detection system than acetic acid or trifluoroacetic acid, which gave a high background response and suppressed the luminescence signal, respectively. However, acetonitrile (which has been previously shown to quench various permanganate chemiluminescence reactions [7,129–131]) was used as the organic modifier. In spite of this, the procedure had impressive limits of detection of 2 nM ibuprofen, 0.2 nM naproxen and 2 nM fenbufen. McDermott et al. reported the determination of glutathione (GSH) in cultured muscle cells based on a rapid reversed-phase HPLC separation (6 min) with permanganate chemiluminescence detection [95]. The procedure was extended to the detection of glutathione disulfide (GSSG), by incorporating thiol blocking and disulfide bond reduction steps. Unlike conventional approaches based on absorbance or fluorescence detection, this procedure did


23

not require derivatization of GSH, thus minimizing error associated with auto-oxidation when establishing the GSH/GSSG ratio as a measure of cellular oxidative stress [95]. McDermott et al. subsequently described the determination of both GSH and GSSG in blood within a single chromatographic run, using a related chemiluminescence reagent containing manganese(IV) [132]. New applications of permanganate chemiluminescence for the detection of total antioxidant status and the measurement of individual antioxidants in plant-derived materials are discussed in Section 3.3. Wu and co-workers used an ion chromatographic separation (12 min) with permanganate chemiluminescence detection for the determination of catecholamines (epinephrine, norepinephrine and dopamine) in urine [64]. The procedure was promoted as ‘highly sensitive and eco-friendly’ due to the absence of any organic modifiers in the mobile phase; the limits of detection (4–30 nM) were certainly better than those previously obtained for these analytes using permanganate chemiluminescence [126,133,134], but the use of an 8% formaldehyde solution to enhance the signal limits the eco-friendliness of the approach. 3.2. Forensic Permanganate chemiluminescence has been utilized for the detection of various (mostly phenolic) controlled substances and related compounds [135], such as opium poppy alkaloids [136], psilocin [137,138] and cannabidiol [139]. In our previous review [9], we described an FIA screening test for heroin in clandestine drug laboratory samples using two chemiluminescence reagents [140]. Heroin evokes a strong response with tris(2,2 bipyridyl)ruthenium(III) and a relatively weak response with permanganate. However, heroin can be rapidly hydrolyzed in alkaline solution to form 6-monoacetylmorphine and morphine, which elicit far greater chemiluminescence with permanganate. More recently, this chemistry has been adapted to sequential injection analysis methodology in a demonstration of the ‘sandwich’ technique for simultaneous dual-reagent chemiluminescence detection [141]. Following on from Toop and co-workers’ use of permanganate chemiluminescence for the HPLC determination of morphine in insects reared on meat spiked at levels typically found in the human tissue of opiate overdose victims [142], the same research group examined the effect of morphine on the growth rate of the native Australian blowfly (Calliphora stygia) reared on mincemeat spiked with morphine [143]. The continued presence of morphine in the meat over the period of the experiment was qualitatively verified using HPLC with permanganate chemiluminescence detection. The growth rates of the insects did not significantly differ from control insects, indicating that C. stygia is a reliable model to assess the post-mortem interval of a corpse containing morphine at any of the concentrations investigated. They also examined the ability of C. stygia to actively excrete morphine, in part using HPLC with permanganate chemiluminescence to detect morphine and its major metabolites in the secretions from the Malpighian tubules of maggots [144]. The chemiluminescent reaction of morphine and permanganate has also been used as a model system to compare the effectiveness of conventional and novel chemiluminescence flow-cell designs (Fig. 2) [145–147] and in conjunction with related morphinan compounds, time-resolved chemiluminescence detection using stopped-flow methodology [60,61]. Holland and co-workers used HPLC with permanganate chemiluminescence detection for the determination of cannabidiol in industrial-grade hemp leaf [139]. The sensitivity of the reagent towards this analyte was much poorer than that reported for morphine [122], but cannabidiol was still one of the two largest peaks observed in the chromatograms for the hemp samples [139]. This

Fig. 2. Photographs of chemiluminescence from the reaction of permanganate and morphine in four different detection flow-cells [157]. (A) A coil of transparent tubing; (B) transparent tubing glued into a spiral channel machined into a polished aluminium plate; (D) a serpentine channel machined into a white polymer chip and sealed with a transparent film; (H) a Teflon disk with machined dual-inlet serpentine channel, contained within a GloCel chemiluminescence detector. Reprinted from Ref. [157] with kind permission from Springer Science and Business Media.

analytical approach may be useful for other cannabinoids, such as 9 -tetrahydrocannabinol in drug-grade cannabis. 3.3. Food and consumer products Recent applications of acidic potassium permanganate chemiluminescence in food science have predominantly involved the detection of antioxidant compounds [27,30,33,131,148–151]. Bellomarino et al. explored the relationship between the phenolic composition of wine and its geographical region [148] or vintage [149] using HPLC separation with permanganate chemiluminescence detection and multivariate data analysis. Moreover, a rapid approach to assess the total phenolic/antioxidant content of wines using simple FIA methodology [152] (discussed in our previous review [9]) was extended to the comparison of fruit juices and tea varieties (Fig. 3) [27], showing reasonable agreement with conventional DPPH• and ABTS•+ assays. Alam and co-workers described the determination of catechin in tea and coffee samples using a simple FIA system with the permanganate reagent immobilized in a silica sol–gel column [30], but considering the number of compounds in tea and coffee samples that have been shown to produce light upon reaction with permanganate [27,150,151], it would be better to attribute the responses obtained in that study [30] to the total catechins in the tea and the total phenolic content of the coffee. Lin et al. reported the determination of total catechins in green teas using a PDMS chip with integrated monolithic column for analyte preconcentration and a chemiluminescence detection zone to which the permanganate reagent was delivered (Fig. 4) [150]. A similar chemiluminescence response was obtained from five different catechin species, and very little interference was observed from other compounds commonly found in teas, suggesting that the approach is suitable for the assessment of total catechin content. Xu et al. described the determination of total protoberberine alkaloids in ethanol extracts of two medicinal plants [14] using the reaction with permanganate in a batch luminometer. Flavonoids,

24


Fig. 3. Total antioxidant capacity in teas established using FIA with permanganate chemiluminescence detection and the DPPH• spectrophotometric approach [27]. Teas: 1: Lipton yellow label; 2: Darjiling; 3: Blackcurrant tea; 4: China black; 5: Prince of Wales; 6: Tetley green; 7: Russian Caravan; 8: Nerada green; 9: Yunnan; 10: Lady Grey; 11: Earl Grey; 12: Irish breakfast; 13: Madura Premium; 14: Traditional afternoon; 15: English breakfast. Tea leaves: 16: Earl Grey; 17: Russian Caravan; 18: English breakfast; 19: Madura green; 20: Irish breakfast. Error bars represent ±1 standard deviation. Reprinted from Food Chemistry, 122, P.S. Francis, J.W. Costin, X.A. Conlan, S.A. Bellomarino, J.A. Barnett, N.W. Barnett, A rapid antioxidant assay based on acidic potassium permanganate chemiluminescence, 926–929, Copyright (2010), with permission from Elsevier.

Fig. 5. Antioxidant screening in complex plant-derived materials using HPLC coupled with (i) UV absorbance, (ii) ABTS•+ assay, (iii) DPPH• assay or (iv) permanganate chemiluminescence, demonstrated using a thyme extract [131]. Reprinted from Analytica Chimica Acta, 684, G.P. McDermott, X.A. Conlan, L.K. Noonan, J.W. Costin, M. Mnatsakanyan, R.A. Shalliker, N.W. Barnett, P.S. Francis, Screening for antioxidants in complex matrices using high performance liquid chromatography with acidic potassium permanganate chemiluminescence detection, 134–141, Copyright (2010), with permission from Elsevier.

Fig. 4. (a) Schematic of microfluidic chip with integrated capillary monolithic column (for extraction of catechins from tea samples) and permanganate chemiluminescence detection. (b) Photograph of the chip on the photodetector. Adapted from Ref. [150] (http://dx.doi.org/10.1039/C1AN15530J) with permission of The Royal Society of Chemistry.

which gave positive interference in one of the samples, were removed by adsorption on an aluminium oxide column. These three procedures [14,30,150], however, have not yet been directly compared to conventional techniques. Permanganate chemiluminescence has been explored as an online post-column assay for ‘high resolution’ antioxidant screening in plant-derived sample matrices (where peak heights ideally correspond to not only the concentration but also the reactivity of individual antioxidant compounds) which has been demonstrated using tea, coffee, juice and spice samples [27,131,151] (Fig. 5). A promising relationship has been shown between antioxidant potential and permanganate chemiluminescence intensity [153], but it should be noted that this mode of detection has also been applied to numerous compounds that would not be considered as antioxidants [9]. In comparison with on-line DPPH• and ABTS•+ radical decolorization assays [154], many of the same peaks were observed for complex samples (Fig. 5), albeit with some differences in selectivity [131,151], which can be attributed to factors such as oxidant strength, reaction pathways and pH [131]. The better agreement between the off-line versions of these assays (used to establish total antioxidant status of samples) [27] is most likely a consequence of the cancellation of differences in selectivity for the large number of antioxidants present in the samples. Nevertheless, the post-column permanganate chemiluminescence detection has several significant advantages over conventional on-line antioxidant screening [154]: faster reagent preparation, superior reagent stability, simpler post-column reaction manifold, and greater compatibility with fast chromatographic separations (stable baseline, positive peaks, reduced post-column peak broadening) [131].


Wołyniec et al. reported the determination of unbound ␣-lipoic acid in several food samples using an isocratic HPLC separation and permanganate chemiluminescence detection, which they enhanced with both sodium polyphosphate and formaldehyde [33]. After commenting that the choice of mobile phase conditions involves a compromise between the best elution times and minimizing the suppression of chemiluminescence by the organic modifier, they suggested that 30% acetonitrile and 70% aqueous KH2 PO4 (adjusted to pH 3) was most appropriate for this application. However, as noted in the previous section, several other research groups have reported strong quenching by acetonitrile, and recommended methanol as the organic modifier for reversed-phase separations coupled with permanganate chemiluminescence [7,129–131]. The use of acetonitrile may have contributed to the significantly poorer limit of detection (6 ␮M) in Wołyniec and co-workers’ HPLC procedure, compared to their preliminary experiments using FIA (0.02 ␮M) [33]. Terry et al. used a similar FIA approach (with an initial off-line partial reduction of the reagent with thiosulfate, rather than on-line merging with formaldehyde) for the determination of ␣-lipoic acid and dihydrolipoic acid [56], for which the limits of detection were 0.3 and 0.08 ␮M, but this was not applied to HPLC analysis of real samples. These studies [33,56], in addition to the determination of readily oxidizable phenols [27,131,151,152] cellular thiols [95] (see Section 3.1) and compounds such as ascorbic acid [130], illustrate that permanganate chemiluminescence is an effective mode of detection for a broad range of antioxidant species. The application of permanganate chemiluminescence to the HPLC determination of Citrus aurantium protoalkaloids (synephrine, octopamine, tyramine and hordenine) in weightloss dietary supplements [155] has been extended to include N-methyltyramine and applied to a wider range of samples [156]. The thioether amino acid l-methionine was identified as a potential interferent when in relatively high concentrations in these samples. The preliminary partial reduction of the permanganate reagent (see Section 2.5) was found to be particularly effective in enhancing the response with these analytes [28,29,157]. After Nie and Lu showed that the banned appetite suppressant fenfluramine could be detected by its enhancing effect on the final stages of the chemiluminescence reaction of permanganate and calcein in alkaline solution (using FIA methodology) [158], Yu et al. derived better sensitivity and presumably greater selectivity using an FIA system with a molecularly imprinted polymer flow cell and detection based on the influence of fenfluramine on the chemiluminescence reaction of permanganate and a sulfonophenylazo-rhodanine compound in acidic solution [159,160]. The concentrations of fenfluramine in weight-loss tonics derived by this procedure were in good agreement with those obtained using a HPLC procedure. A similar approach was used to determine sorbic acid preservative in milk and fruit juices [161]. Yu and co-workers also developed a high-throughput batch approach to determine melamine in milk products, based on a 96-well microplate modified with a molecularly imprinted sol–gel film (Fig. 6) [162]. Bound melamine was detected by permanganate chemiluminescence in a commercial reader to a limit of 0.02 ␮g mL−1 and the results were in good agreement with a HPLC procedure. Manzoori et al. subsequently published a detection system based on the inhibiting effect of melamine on the chemiluminescence reaction of permanganate, formaldehyde and gold nanoparticles (see Section 2.11) [17]. Although much more sensitive (limit of detection of 0.02 pg mL−1 ), their approach was less selective. Vitamin C, for example, interfered at a concentration ratio of 0.1 [17] compared to ∼200 for the previous method [162]. A preliminary application of the approach to powdered milk products was limited to percentage recoveries [17].

25

Fig. 6. Preparation of a 96-well microplate with molecularly imprinted sol–gel film for the selective detection of melamine [162]. Reprinted from Analytica Chimica Acta, 651, J. Yu, C. Zhang, P. Dai, S. Ge, Highly selective molecular recognition and high throughput detection of melamine based on molecularly imprinted sol–gel film, 209–214, Copyright (2009), with permission from Elsevier.

Satienperakul and co-workers reported the determination of sulfite (down to 0.2 mg L−1 ) in fresh and pickled food samples based on the chemiluminescence reaction with permanganate [163]. Using FIA methodology, the analyte was converted to sulfur dioxide in acidic solution, separated from the sample using a pervaporation unit, and then merged with the reagent. Both sodium polyphosphate and rhodamine B were used as enhancers (see Section 2.8 for a discussion of the influence of these enhancers on the reaction of permanganate and sulfite). The results obtained for a variety of foods with this procedure were in good agreement with a conventional approach. Ethanol was the only common constituent of foods found to interfere (when at very high concentrations) [163], and therefore the procedure was deemed not suitable for the analysis of alcoholic beverages. Previously published procedures based on the chemiluminescent oxidation of sulfite [164,165] were successfully applied to beer and wine, although this may only have been possible because of the greater sensitivity of those procedures (limits of detection of 0.03 and 0.06 mg L−1 ), enabling greater dilution of the alcoholic samples. Nevertheless, the inclusion of the pervaporation unit [163] should impart much greater overall selectivity for a wide variety of food samples. 3.4. Agricultural and environmental At the time of our previous review [9], we found that a large number of pesticides, herbicides, pollutants, and inorganic species had been determined in natural waters, soils, grains and commercial formulations with permanganate chemiluminescence using flow analysis methodologies (including FIA, SIA and multicommutation assemblies). Since then, some new procedures have emerged [15,26,59,65,114,166] (see Tables 1 and 2). These were often successfully used to analyze samples that were spiked with (or known to contain) a single species that elicits chemiluminescence with this reagent. In commercial formulations, the matrix may be sufficiently well known and free from interferences for simple flow analysis methodology to be suitable, but as with clinical samples

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(discussed in Section 3.1), agricultural and environmental samples may contain numerous compounds that respond to permanganate. Again, various approaches have been utilized to extend this mode of detection to new species or impart greater selectivity towards particular target analytes. López Malo and Martínez Calatayud determined the herbicide buminafos using a flow analysis (multicommutation) assembly in which the sample was degraded with hydrogen peroxide in an on-line photo-reactor before permanganate chemiluminescence detection [166] – a strategy that Martínez Calatayud’s group had previously found effective for many environmentally important analytes [167–171]. Waseem and co-workers determined vanadium in seawater using FIA incorporating on-line reduction of vanadium(IV)/(V) found in the sample to lower oxidation states that elicit light with acidic potassium permanganate and formaldehyde [172]. An examination of the influence other cations revealed Fe(II), Mn(II) and Sn(II) as potential interferences (which is perhaps not surprising considering that each of these species has previously been detected by permanganate chemiluminescence systems [173–175]). However, the typical concentrations of these ions in seawater do not present a significant problem. Using this procedure, vanadium was successfully determined in two seawater certified reference materials [172]. Dong and Dayou determined formaldehyde in leather wastewater based on its enhancing effect (see Section 2.6) on the chemiluminescent reaction of permanganate and ninhydrin, using FIA [59]. The limit of detection was 2 × 10−8 M formaldehyde and the results for three wastewater samples were in good agreement with those obtained using a conventional spectrophotometric method. Fujimori and co-workers explored the chemiluminescence detection of sulfide in deep seawater, based on its reaction with permanganate [94]. The enhancer, CAPS, promoted the light-producing pathway involving an emitter derived from the reductant (see Section 2.9) rather than the oxidant (Section 2.1). Moreover, interference from species that react with permanganate to generate the characteristic red emission from Mn(II)* was minimized using a photomultiplier tube that was not sensitive in that region [94]. Although the procedure is promising, the application was limited to percentage recoveries in spiked seawaters. Other researchers have continued to exploit the combined response from many compounds with this chemiluminescence reagent. After Fujimori and co-workers proposed that the chemiluminescence signal with permanganate could be used as a measure of total organic pollutants in fresh waters and seawater as a rapid alternative to ‘chemical oxygen demand’ methodologies [176,177], Yao and co-workers devised a procedure in which the dissolved organic matter in natural waters or factory wastewater was digested by excess permanganate, with the remaining oxidant quantified by its chemiluminescence reaction with glutaraldehyde in a 96-well plate [22]. The procedure showed better correlation (r = 0.998) with a conventional titrimetric chemical oxygen demand methodology than that of Fujimori and co-workers’ (r = 0.864 [176] and 0.936 [177]) and although the approach of Yao et al. required considerably more time, the ability to carry out the chemiluminescence analysis in a microplate format allowed many simultaneous assays to be performed. Extending the research of Townshend and Wheatley on the permanganate chemiluminescence detection of carbonyl compounds after derivatization with 2,4-dinitrophenylhydrazine [178,179], Giokas and co-workers developed an FIA procedure that included on-line derivatization to determine total carbonyl content (e.g. acetone, formaldehyde, acetaldehyde) in natural waters and drinking water [20]. Although other compounds in the samples were found to elicit light with the reagent, the signal from carbonyls could be established using the difference between the signals with and without the sample (to determine a reagent blank) and the selective derivatizing agent (to establish a blank response from other

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The importance of chain length for the polyphosphate enhancement of acidic potassium permanganate chemiluminescence.

Acidic Potassium Permanganate Chemiluminescence for the Determination of Antioxidant Potential in Three Cultivars of Ocimum basilicum.

Potassium permanganate ingestion as a suicide attempt.

Genotoxic activity of potassium permanganate in acidic solutions.

Screening of cannabinoids in industrial-grade hemp using two-dimensional liquid chromatography coupled with acidic potassium permanganate chemiluminescence detection.

Potassium permanganate-acridine yellow chemiluminescence system for the determination of fluvoxamine, isoniazid and ceftriaxone.

Potassium Permanganate Poisoning: A Nonfatal Outcome.

Potassium permanganate-glutaraldehyde chemiluminescence system catalyzed by gold nanoprisms toward selective determination of fluoride.

Suicidal ingestion of potassium permanganate.

Suicidal ingestion of potassium permanganate crystals: a rare encounter.

Flow injection determination of diclofenac sodium based on its sensitizing effect on the chemiluminescent reaction of acidic potassium permanganate-formaldehyde.

Determination of ethanol using permanganate-CdS quantum dot chemiluminescence system.

A review of recent advances in chemiluminescence detection using nano-colloidal manganese(IV).

The determination of total mercury in biological tissues by a modified potassium permanganate procedure.

The use of ninhydrin as a reagent for the reversible modification of arginine residues in proteins.

Permanganate of Potassium and Chloroform in Snake Bites.

Fetal fibronectin as a biomarker of preterm labor: a review of the literature and advances in its clinical use.

Application of chemiluminescence in the analysis of wastewaters - a review.

Potassium permanganate as an in situ probe for B-Z and Z-Z junctions.

Base modifications in plasmid DNA caused by potassium permanganate.

Chemiluminescence high performance liquid chromatography of corticosteroids using lucigenin as post-column reagent.

Haemorrhagic pancreatitis--a cause of death in severe potassium permanganate poisoning.

Gold nanoparticles bifunctionalized by chemiluminescence reagent and catalyst metal complexes: synthesis and unique chemiluminescence property.

Light generation with Fenton's reagent. Its relationship to granulocyte chemiluminescence.