Editorial
For reprint orders, please contact [email protected]
What is the potential of measuring the enantiomeric ratio of drugs using supercritical fluid chromatography–MS? “Supercritical fluid chromatography allows fast and efficient separation of enantiomers.” Keywords: bioanalysis • enantiomeric ratio • mass spectrometry • metabolism • pharmaceuticals • quality control • supercritical fluid chromatography
Analytical chemists are always looking for more efficient techniques to meet analytical challenges of today’s regulatory and scientific requirements. One technique that has made drastic improvements in recent years is supercritical fluid chromatography (SFC). Since its early days, this separation technique has emerged as a powerful tool for both analytical and preparative scientists. In 2012, new instruments for analytical purpose were introduced that offer reliability, robustness and sensitivity never before possible. Since then, the interest in this technique was renewed. Indicated by the number of peerreviewed articles, analytical SFC progressively increased within the last 25 years. The use of supercritical fluids (sc) as mobile phases in chromatography presents unique advantages compared with traditional HPLC: low viscosity and high diffusivity allow faster and more efficient separations than HPLC. Coupling SFC to MS instruments is straightforward as carbon dioxide is easily eliminated during desolvation and provides low LODs and LOQs as well as additional structural information [1] . A wide range of analytes may be covered by SFC, including nonpolar, polar and charged compounds [2] . Applications for a broad variety of polarity are reported ranging from hydrocarbons, esters, amines, aldehydes, alcohols, carboxylic acids, amides, amphoterics, complexes to peptides. In general, supercritical carbon dioxide (CO2,sc) is used as mobile phase due to its easy generation and low toxicity. The more polar analytes can
10.4155/BIO.14.255 © 2014 Future Science Ltd
be separated by addition of modifiers and additives (mainly methanol and also even water). Thus, SFC is emerging as a technique of choice for enantioselective separations and as replacement for HPLC methods [3] . A positive side effect is the reduction of toxic solvents compared with HPLC, which can minimize waste and decrease the cost of chiral separations significantly. SFC–MS/MS in analyses of pharmaceuticals Triggered by the thalidomide tragedy, the effort of the pharmaceutical industry to develop safe and effective drugs has increased tremendously. Many drug candidates under development are chiral and their specific stereochemistry affects drug action, metabolism and toxicity. Due to regulatory demands, most of the drug candidates lately approved are pure enantiomers [4] . Thus high-throughput analyses and purification of enantiomers are important parts of drug discovery. Purification scientists have recognized the value of SFC for preparative separation for many years to provide enantiopure compounds for pharmacological testing. Pharmacopoeias such as PhEur already mention SFC as analytical technique since years, however currently with no examples in monographs. Analytical separations, especially in fast chiral screening, are challenging as it is almost impossible to predict which chiral stationary phase and mobile phase combination will provide successful separation. A generic chiral screening strategy is therefore
Bioanalysis (2014) 6(24), 3267–3270
Maria Kristina Parr Institute of Pharmacy, Freie Universität Berlin, Königin-Luise-Str. 2+4, 14195 Berlin, Germany Author for correspondence: [email protected]
Alexander H Schmidt Institute of Pharmacy, Freie Universität Berlin, Königin-Luise-Str. 2+4, 14195 Berlin, Germany Chromicent GmbH, Rudower Chaussee 29, 12489 Berlin, Germany
part of
ISSN 1757-6180
3267
Editorial Parr & Schmidt helpful and recent publications proved its performance and robustness for resolution of hundreds of chiral molecules with a success rate exceeding 95% utilizing SFC [5–7] . One example is the successful SFC–MS/MS analysis of the enantiomers of primaquine diphosphate (differences in toxicity) [8] . Even multi-analyte methods involving enantiomeric compounds can be developed fast and efficiently. In combination with MS, they are valuable tools for controlling stereoselective synthesis (e.g., cinnamonitrile [9]) or pharmaceutical quality assurance with respect to simultaneous identification, purity determination and assay [10] . SFC–MS may even shorten the total analyses time by sample pooling [6] . Upscaling to preparative needs is easily possible after optimization.
“...recent publications proved its performance and robustness for resolution of hundreds of chiral molecules with a success rate exceeding 95%...
”
Chiral APIs may undergo racemization during storage or body passage. As known for thalidomide acidic hydrogen atoms at chiral centers may lead to an inversion via the achiral tautomer. This may occur in vivo as well as in solutions. Other chiral drugs may undergo racemization during storage by irradiation or by nucleophilic substitution under acidic conditions (e.g., phenylethanolamines). Racemization may also occur by enzymatic processes as reported for chiral 2-arylpropionic acids (e.g., ibuprofen conversion by α-methylacylCoA racemase). In all these cases, SFC–MS/MS may be used to successfully monitor the stability by enantiomeric ratio determination. Also in uncovering illegal or counterfeit drugs or determination of drug origin SFC–MS/MS with chiral separation may be used for comprehensive analyses with alternative selectivity and complementarity to LC–MS/MS [1] . SFC–MS/MS in pharmacokinetics Differences in the pharmacokinetic behavior may occur after administration of enantiomeric mixtures due to chiral recognition of metabolic enzymes, receptors or transporter molecules. This may result in altered tissue distribution or elimination of the mirror images. As one of the enantiomers is generally recognized as eutomer, its concentration in target tissues is relevant for the desired pharmacological activity, while the distomer concentration is especially relevant for undesired effects. Thus, an enantioselective determination of chiral drugs is of high relevance in clinical trials. Especially in cases where an enantiodiscrimination is observed during detoxification (e.g., for the anticoagulant warfarin, the antidepressants citalopram, mianserin, the anticonvulsant mephenyt-
3268
Bioanalysis (2014) 6(24)
oin, and the drugs of abuse MDMA and MDEA) enzymatic polymorphisms play an important role for the observed plasma levels and enantiomeric ratios [11–13] . As the concentrations of drugs in biological specimen are generally low, SFC–MS/MS offers perfect separation combined with very low detection limits [11] . If coupled to high resolution MS, for example, QTOFMS, simultaneous identification and enantioseparation of metabolites can be performed. Even the determination of conjugates has proven possible by addition of modifiers and additives. Thus, enantioseparation of sulfoconjugates in biological samples may be carried out by SFC–MS/MS as well. Other conjugates mainly form diastereomers and are thereby much easier separated. If SPE is applied for sample preparation prior to SFC in general organic solvents are used for the elution. Relatively large amounts of apolar eluates can be perfectly injected in SFC as the polarity of CO2,sc is comparable to heptane [14] . However, in contrast to common thinking, direct injection of aqueous biological samples SFC may also be performed using water as modifier (up to 30% mainly in combination with alcohols). SFC–MS/MS in doping control As special applications of pharmacokinetics the enantiomeric ratio may be determined in human sports doping control. Substances that may result in performance enhancement are prohibited in athletes. They are mentioned in the ‘List of Prohibited Substances and Methods’ yearly updated by the World Anti-Doping Agency. Recently, unintentional intake of doping substances due to food contamination was reported, especially for the anabolic β-2 agonist clenbuterol. In some countries it is extensively misused in animal feeding as repartitioning agent. In livestock, enantiomers are reported to be distributed unequally resulting in a biased enantiomeric ratio while all available drug preparations contain clenbuterol as racemate. In human urine, no enantiodiscrimination was found. Thus, the potential of the determination of the ratio of clenbuterol enantiomers was discussed for discrimination of illegal and unintentional administration. The latter may result in reduced sanctions of athletes. First promising results were obtained by SFC–MS/MS analysis of urine samples [15] . Other possibilities to prove athlete’s testimonials may include the determination of enantiomeric ratios of ephedrine derivatives by SFC–MS/MS. Natural extracts of the Chinese plant Ma Huang contain the diastereomers nor-(pseudo-)ephedrine, (pseudo-)ephedrine and methyl-(pseudo-) ephedrine each in enantiopure form [16] . If chemical synthesis is used, mixtures with varying enantiomeric com-
future science group
What is the potential of measuring the enantiomeric ratio of drugs using SFC–MS?
positions may result. Their pattern in urine can be used to trace-back the source of the administered preparation. For valuation of the administration of some other doping substances, the route of administration plays an important role: only systemic administrations of glucocorticosteroids or adrenaline are prohibited at incompetition testing. β-2 sympathomimetics are generally prohibited in- and out-of-competition. However therapeutical administration of salbutamol, formoterol or salmeterol by inhalation is not prohibited according to current regulations. Potential differences in pharmacokinetics of the enantiomers of adrenaline or β-2 agonists during distribution and metabolism may result in a shift of the enantiomeric ratio. Thus, the determination of the ratio of the parent and its metabolites may substantiate the athlete’s statement. With its proven potential for enantiomer determination at picogram per milliliter concentrations, SFC–MS/MS is the method of choice for these ultratrace-level determinations. SFC–MS/MS in forensics For the valuation of drug seizures, the enantiomeric ratio currently is not relevant, as current legal values do not distinguish between enantiomers. However, the enantiomeric ratio of drugs may also contribute to the elucidation of fatalities. As shown for methadone and its metabolites, the enantiomeric ratio may elucidate whether an intoxication might have contributed to death or not. The enantiomeric ratio of drugs of abuse has also been used to estimate the time of MDMA ingestion [17] or as the enantiomeric ratio of detected metabolites, methamphetamine and amphetamine, may be used to trace-back a selegelin administration in case of nondetection of the rapidly metabolized parent compound [18] . Besides the separation of chiral molecules, structural analogs and conjugates (for example steroids) are another class of components, which are difficult to separate and analyze due to their similarity [14] . References 1
2
3
Grand-Guillaume Perrenoud A, Veuthey J-L, Guillarme D. Coupling state-of-the-art supercritical fluid chromatography and mass spectrometry: from hyphenation interface optimization to high-sensitivity analysis of pharmaceutical compounds. J. Chromatogr. A 1339, 174–184 (2014). Pinkston JD, Wen D, Morand KL, Tirey DA, Stanton DT. Comparison of LC/MS and SFC/MS for screening of a large and diverse library of pharmaceutically relevant compounds. Anal. Chem. 78(21), 7467–7472 (2006). De Klerck K, Mangelings D, Vander Heyden Y. Supercritical fluid chromatography for the enantioseparation of pharmaceuticals. J. Pharm. Biomed. Anal. 69(0), 77–92 (2012).
future science group
Editorial
SFC–MS/MS in biological analyses Also in biological control, SFC–MS/MS has a high potential in enantioseparation, for example, in authenticity control of plants and spices. SFC–MS/MS analysis of enantiomeric amino acids may also be used for chronological age estimation [19] . Conclusion SFC allows fast and efficient separation of enantiomers. In our opinion, the recent developments of instruments provide reliable and robust analysis. Thus, SFC technology will be used in many fields of routine and research applications in the near future. The combination of SFC–MS/MS allows for highly selective detection with very low LODs, especially relevant in analyses, where the amount of analyte is very limited (e.g., low concentrated, expensive or only available as test compound). As CO2,sc combines very good mobile phase conditions and safe use with ease of access and perfect green properties, we believe that alternative supercritical fluids will hardly be used and reserved to niche applications. The variety of potential applications covers pharmaceutical research and development and forensic research, but also fine chemicals and food and environment. Increasing numbers of analyses will be performed by SFC not only in routine applications but also in research projects. When coupled to QTOF-MS detectors, it will also be used for metabolomics applications in the future [20] . Financial & competing interests disclosure The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending or royalties. No writing assistance was utilized in the production of this manuscript. 4
Agranat I, Caner H, Caldwell J. Putting chirality to work: the strategy of chiral switches. Nat. Rev. Drug Discov. 1(10), 753–768 (2002).
5
Maftouh M, Granier-Loyaux C, Chavana E et al. Screening approach for chiral separation of pharmaceuticals. Part III. Supercritical fluid chromatography for analysis and purification in drug discovery. J. Chromatogr. A 1088(1–2), 67–81 (2005).
6
Zhao Y, Woo G, Thomas S, Semin D, Sandra P. Rapid method development for chiral separation in drug discovery using sample pooling and supercritical fluid chromatography–mass spectrometry. J. Chromatogr. A 1003(1–2), 157–166 (2003).
7
Franco P, Zhang T. Common screening approaches for efficient analytical method development in LC and SFC on
www.future-science.com
3269
Editorial Parr & Schmidt columns packed with immobilized polysaccharide-derived chiral stationary phases. In: Chiral Separations. Scriba, GKE (Ed.) Humana Press, NY, USA, 113–126 (2013). 8
9
10
11
12
3270
Brondz I, Ekeberg D, Bell DS et al. Nature of the main contaminant in the drug primaquine diphosphate: SFC and SFC–MS methods of analysis. J. Pharm. Biomed. Anal. 43(3), 937–944 (2007). Alexander AJ, Staab A. Use of achiral/chiral SFC/MS for the profiling of isomeric cinnamonitrile/hydrocinnamonitrile products in chiral drug synthesis. Anal. Chem. 78(11), 3835–3838 (2006). Ren-Qi W, Teng-Teng O, Siu-Choon N, Weihua T. Recent advances in pharmaceutical separations with supercritical fluid chromatography using chiral stationary phases. Trends Analyt. Chem. 37, 83–100 (2012). Coe RA, Rathe JO, Lee JW. Supercritical fluid chromatography-tandem mass spectrometry for fast bioanalysis of R/S-warfarin in human plasma. J. Pharm. Biomed. Anal. 42(5), 573–580 (2006). Brunnenberg M, Kovar KA. Stereospecific analysis of ecstasy-like N-ethyl-3,4-methylenedioxyamphetamine and its metabolites in humans. J. Chromatogr. B Biomed. Sci. Appl. 751(1), 9–18 (2001).
13
Srinivas NR. Simultaneous chiral analyses of multiple analytes: case studies, implications and method development considerations. Biomed. Chromatogr. 18(10), 759–784 (2004).
14
Kohler I, Guillarme D. Multi-target screening of biological samples using LC–MS/MS: focus on chromatographic innovations. Bioanalysis 6(9), 1255–1273 (2014).
Bioanalysis (2014) 6(24)
15
Parr MK, Bokland MH, Liebetrau F, Schmidt AH, Schänzer W, Sterk SS. Enantiomeric separation of clenbuterol as analytical strategy to distinguish abuse from meat contamination. In: Recent Advances in Dope Analysis. Schänzer W, Geyer H, Gotzmann A, Mareck U (Eds.). Sportverlag Strauß, Cologne, Germany (2013).
16
Chou TQ. The preparation and properties of ephedrine and its salts. J. Biol. Chem. 70(1), 109–114 (1926).
17
Schwaninger AE, Meyer MR, Barnes AJ et al. Stereoselective urinary MDMA (ecstasy) and metabolites excretion kinetics following controlled MDMA administration to humans. Biochem. Pharmacol. 83(1), 131–138 (2012).
18
Jantos R, Skopp G. Postmortem blood and tissue concentrations of R- and S-enantiomers of methadone and its metabolite EDDP. Forensic Sci. Int. 226(1–3), 254–260 (2013).
19
Yamamoto T, Ohtani S. Estimation of chronological age from the racemization rate of L- and D-aspartic acid: how to completely separate enantiomers from dentin. Methods Mol. Biol. 794, 265–272 (2012).
20
Jones MD, Rainville PD, Isaac G, Wilson ID, Smith NW, Plumb RS. Ultra high resolution SFC–MS as a high throughput platform for metabolic phenotyping: application to metabolic profiling of rat and dog bile. J. Chromatogr. B Biomed. Sci. Appl. 966, 200–207 (2014).
future science group
For reprint orders, please contact [email protected]
What is the potential of measuring the enantiomeric ratio of drugs using supercritical fluid chromatography–MS? “Supercritical fluid chromatography allows fast and efficient separation of enantiomers.” Keywords: bioanalysis • enantiomeric ratio • mass spectrometry • metabolism • pharmaceuticals • quality control • supercritical fluid chromatography
Analytical chemists are always looking for more efficient techniques to meet analytical challenges of today’s regulatory and scientific requirements. One technique that has made drastic improvements in recent years is supercritical fluid chromatography (SFC). Since its early days, this separation technique has emerged as a powerful tool for both analytical and preparative scientists. In 2012, new instruments for analytical purpose were introduced that offer reliability, robustness and sensitivity never before possible. Since then, the interest in this technique was renewed. Indicated by the number of peerreviewed articles, analytical SFC progressively increased within the last 25 years. The use of supercritical fluids (sc) as mobile phases in chromatography presents unique advantages compared with traditional HPLC: low viscosity and high diffusivity allow faster and more efficient separations than HPLC. Coupling SFC to MS instruments is straightforward as carbon dioxide is easily eliminated during desolvation and provides low LODs and LOQs as well as additional structural information [1] . A wide range of analytes may be covered by SFC, including nonpolar, polar and charged compounds [2] . Applications for a broad variety of polarity are reported ranging from hydrocarbons, esters, amines, aldehydes, alcohols, carboxylic acids, amides, amphoterics, complexes to peptides. In general, supercritical carbon dioxide (CO2,sc) is used as mobile phase due to its easy generation and low toxicity. The more polar analytes can
10.4155/BIO.14.255 © 2014 Future Science Ltd
be separated by addition of modifiers and additives (mainly methanol and also even water). Thus, SFC is emerging as a technique of choice for enantioselective separations and as replacement for HPLC methods [3] . A positive side effect is the reduction of toxic solvents compared with HPLC, which can minimize waste and decrease the cost of chiral separations significantly. SFC–MS/MS in analyses of pharmaceuticals Triggered by the thalidomide tragedy, the effort of the pharmaceutical industry to develop safe and effective drugs has increased tremendously. Many drug candidates under development are chiral and their specific stereochemistry affects drug action, metabolism and toxicity. Due to regulatory demands, most of the drug candidates lately approved are pure enantiomers [4] . Thus high-throughput analyses and purification of enantiomers are important parts of drug discovery. Purification scientists have recognized the value of SFC for preparative separation for many years to provide enantiopure compounds for pharmacological testing. Pharmacopoeias such as PhEur already mention SFC as analytical technique since years, however currently with no examples in monographs. Analytical separations, especially in fast chiral screening, are challenging as it is almost impossible to predict which chiral stationary phase and mobile phase combination will provide successful separation. A generic chiral screening strategy is therefore
Bioanalysis (2014) 6(24), 3267–3270
Maria Kristina Parr Institute of Pharmacy, Freie Universität Berlin, Königin-Luise-Str. 2+4, 14195 Berlin, Germany Author for correspondence: [email protected]
Alexander H Schmidt Institute of Pharmacy, Freie Universität Berlin, Königin-Luise-Str. 2+4, 14195 Berlin, Germany Chromicent GmbH, Rudower Chaussee 29, 12489 Berlin, Germany
part of
ISSN 1757-6180
3267
Editorial Parr & Schmidt helpful and recent publications proved its performance and robustness for resolution of hundreds of chiral molecules with a success rate exceeding 95% utilizing SFC [5–7] . One example is the successful SFC–MS/MS analysis of the enantiomers of primaquine diphosphate (differences in toxicity) [8] . Even multi-analyte methods involving enantiomeric compounds can be developed fast and efficiently. In combination with MS, they are valuable tools for controlling stereoselective synthesis (e.g., cinnamonitrile [9]) or pharmaceutical quality assurance with respect to simultaneous identification, purity determination and assay [10] . SFC–MS may even shorten the total analyses time by sample pooling [6] . Upscaling to preparative needs is easily possible after optimization.
“...recent publications proved its performance and robustness for resolution of hundreds of chiral molecules with a success rate exceeding 95%...
”
Chiral APIs may undergo racemization during storage or body passage. As known for thalidomide acidic hydrogen atoms at chiral centers may lead to an inversion via the achiral tautomer. This may occur in vivo as well as in solutions. Other chiral drugs may undergo racemization during storage by irradiation or by nucleophilic substitution under acidic conditions (e.g., phenylethanolamines). Racemization may also occur by enzymatic processes as reported for chiral 2-arylpropionic acids (e.g., ibuprofen conversion by α-methylacylCoA racemase). In all these cases, SFC–MS/MS may be used to successfully monitor the stability by enantiomeric ratio determination. Also in uncovering illegal or counterfeit drugs or determination of drug origin SFC–MS/MS with chiral separation may be used for comprehensive analyses with alternative selectivity and complementarity to LC–MS/MS [1] . SFC–MS/MS in pharmacokinetics Differences in the pharmacokinetic behavior may occur after administration of enantiomeric mixtures due to chiral recognition of metabolic enzymes, receptors or transporter molecules. This may result in altered tissue distribution or elimination of the mirror images. As one of the enantiomers is generally recognized as eutomer, its concentration in target tissues is relevant for the desired pharmacological activity, while the distomer concentration is especially relevant for undesired effects. Thus, an enantioselective determination of chiral drugs is of high relevance in clinical trials. Especially in cases where an enantiodiscrimination is observed during detoxification (e.g., for the anticoagulant warfarin, the antidepressants citalopram, mianserin, the anticonvulsant mephenyt-
3268
Bioanalysis (2014) 6(24)
oin, and the drugs of abuse MDMA and MDEA) enzymatic polymorphisms play an important role for the observed plasma levels and enantiomeric ratios [11–13] . As the concentrations of drugs in biological specimen are generally low, SFC–MS/MS offers perfect separation combined with very low detection limits [11] . If coupled to high resolution MS, for example, QTOFMS, simultaneous identification and enantioseparation of metabolites can be performed. Even the determination of conjugates has proven possible by addition of modifiers and additives. Thus, enantioseparation of sulfoconjugates in biological samples may be carried out by SFC–MS/MS as well. Other conjugates mainly form diastereomers and are thereby much easier separated. If SPE is applied for sample preparation prior to SFC in general organic solvents are used for the elution. Relatively large amounts of apolar eluates can be perfectly injected in SFC as the polarity of CO2,sc is comparable to heptane [14] . However, in contrast to common thinking, direct injection of aqueous biological samples SFC may also be performed using water as modifier (up to 30% mainly in combination with alcohols). SFC–MS/MS in doping control As special applications of pharmacokinetics the enantiomeric ratio may be determined in human sports doping control. Substances that may result in performance enhancement are prohibited in athletes. They are mentioned in the ‘List of Prohibited Substances and Methods’ yearly updated by the World Anti-Doping Agency. Recently, unintentional intake of doping substances due to food contamination was reported, especially for the anabolic β-2 agonist clenbuterol. In some countries it is extensively misused in animal feeding as repartitioning agent. In livestock, enantiomers are reported to be distributed unequally resulting in a biased enantiomeric ratio while all available drug preparations contain clenbuterol as racemate. In human urine, no enantiodiscrimination was found. Thus, the potential of the determination of the ratio of clenbuterol enantiomers was discussed for discrimination of illegal and unintentional administration. The latter may result in reduced sanctions of athletes. First promising results were obtained by SFC–MS/MS analysis of urine samples [15] . Other possibilities to prove athlete’s testimonials may include the determination of enantiomeric ratios of ephedrine derivatives by SFC–MS/MS. Natural extracts of the Chinese plant Ma Huang contain the diastereomers nor-(pseudo-)ephedrine, (pseudo-)ephedrine and methyl-(pseudo-) ephedrine each in enantiopure form [16] . If chemical synthesis is used, mixtures with varying enantiomeric com-
future science group
What is the potential of measuring the enantiomeric ratio of drugs using SFC–MS?
positions may result. Their pattern in urine can be used to trace-back the source of the administered preparation. For valuation of the administration of some other doping substances, the route of administration plays an important role: only systemic administrations of glucocorticosteroids or adrenaline are prohibited at incompetition testing. β-2 sympathomimetics are generally prohibited in- and out-of-competition. However therapeutical administration of salbutamol, formoterol or salmeterol by inhalation is not prohibited according to current regulations. Potential differences in pharmacokinetics of the enantiomers of adrenaline or β-2 agonists during distribution and metabolism may result in a shift of the enantiomeric ratio. Thus, the determination of the ratio of the parent and its metabolites may substantiate the athlete’s statement. With its proven potential for enantiomer determination at picogram per milliliter concentrations, SFC–MS/MS is the method of choice for these ultratrace-level determinations. SFC–MS/MS in forensics For the valuation of drug seizures, the enantiomeric ratio currently is not relevant, as current legal values do not distinguish between enantiomers. However, the enantiomeric ratio of drugs may also contribute to the elucidation of fatalities. As shown for methadone and its metabolites, the enantiomeric ratio may elucidate whether an intoxication might have contributed to death or not. The enantiomeric ratio of drugs of abuse has also been used to estimate the time of MDMA ingestion [17] or as the enantiomeric ratio of detected metabolites, methamphetamine and amphetamine, may be used to trace-back a selegelin administration in case of nondetection of the rapidly metabolized parent compound [18] . Besides the separation of chiral molecules, structural analogs and conjugates (for example steroids) are another class of components, which are difficult to separate and analyze due to their similarity [14] . References 1
2
3
Grand-Guillaume Perrenoud A, Veuthey J-L, Guillarme D. Coupling state-of-the-art supercritical fluid chromatography and mass spectrometry: from hyphenation interface optimization to high-sensitivity analysis of pharmaceutical compounds. J. Chromatogr. A 1339, 174–184 (2014). Pinkston JD, Wen D, Morand KL, Tirey DA, Stanton DT. Comparison of LC/MS and SFC/MS for screening of a large and diverse library of pharmaceutically relevant compounds. Anal. Chem. 78(21), 7467–7472 (2006). De Klerck K, Mangelings D, Vander Heyden Y. Supercritical fluid chromatography for the enantioseparation of pharmaceuticals. J. Pharm. Biomed. Anal. 69(0), 77–92 (2012).
future science group
Editorial
SFC–MS/MS in biological analyses Also in biological control, SFC–MS/MS has a high potential in enantioseparation, for example, in authenticity control of plants and spices. SFC–MS/MS analysis of enantiomeric amino acids may also be used for chronological age estimation [19] . Conclusion SFC allows fast and efficient separation of enantiomers. In our opinion, the recent developments of instruments provide reliable and robust analysis. Thus, SFC technology will be used in many fields of routine and research applications in the near future. The combination of SFC–MS/MS allows for highly selective detection with very low LODs, especially relevant in analyses, where the amount of analyte is very limited (e.g., low concentrated, expensive or only available as test compound). As CO2,sc combines very good mobile phase conditions and safe use with ease of access and perfect green properties, we believe that alternative supercritical fluids will hardly be used and reserved to niche applications. The variety of potential applications covers pharmaceutical research and development and forensic research, but also fine chemicals and food and environment. Increasing numbers of analyses will be performed by SFC not only in routine applications but also in research projects. When coupled to QTOF-MS detectors, it will also be used for metabolomics applications in the future [20] . Financial & competing interests disclosure The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending or royalties. No writing assistance was utilized in the production of this manuscript. 4
Agranat I, Caner H, Caldwell J. Putting chirality to work: the strategy of chiral switches. Nat. Rev. Drug Discov. 1(10), 753–768 (2002).
5
Maftouh M, Granier-Loyaux C, Chavana E et al. Screening approach for chiral separation of pharmaceuticals. Part III. Supercritical fluid chromatography for analysis and purification in drug discovery. J. Chromatogr. A 1088(1–2), 67–81 (2005).
6
Zhao Y, Woo G, Thomas S, Semin D, Sandra P. Rapid method development for chiral separation in drug discovery using sample pooling and supercritical fluid chromatography–mass spectrometry. J. Chromatogr. A 1003(1–2), 157–166 (2003).
7
Franco P, Zhang T. Common screening approaches for efficient analytical method development in LC and SFC on
www.future-science.com
3269
Editorial Parr & Schmidt columns packed with immobilized polysaccharide-derived chiral stationary phases. In: Chiral Separations. Scriba, GKE (Ed.) Humana Press, NY, USA, 113–126 (2013). 8
9
10
11
12
3270
Brondz I, Ekeberg D, Bell DS et al. Nature of the main contaminant in the drug primaquine diphosphate: SFC and SFC–MS methods of analysis. J. Pharm. Biomed. Anal. 43(3), 937–944 (2007). Alexander AJ, Staab A. Use of achiral/chiral SFC/MS for the profiling of isomeric cinnamonitrile/hydrocinnamonitrile products in chiral drug synthesis. Anal. Chem. 78(11), 3835–3838 (2006). Ren-Qi W, Teng-Teng O, Siu-Choon N, Weihua T. Recent advances in pharmaceutical separations with supercritical fluid chromatography using chiral stationary phases. Trends Analyt. Chem. 37, 83–100 (2012). Coe RA, Rathe JO, Lee JW. Supercritical fluid chromatography-tandem mass spectrometry for fast bioanalysis of R/S-warfarin in human plasma. J. Pharm. Biomed. Anal. 42(5), 573–580 (2006). Brunnenberg M, Kovar KA. Stereospecific analysis of ecstasy-like N-ethyl-3,4-methylenedioxyamphetamine and its metabolites in humans. J. Chromatogr. B Biomed. Sci. Appl. 751(1), 9–18 (2001).
13
Srinivas NR. Simultaneous chiral analyses of multiple analytes: case studies, implications and method development considerations. Biomed. Chromatogr. 18(10), 759–784 (2004).
14
Kohler I, Guillarme D. Multi-target screening of biological samples using LC–MS/MS: focus on chromatographic innovations. Bioanalysis 6(9), 1255–1273 (2014).
Bioanalysis (2014) 6(24)
15
Parr MK, Bokland MH, Liebetrau F, Schmidt AH, Schänzer W, Sterk SS. Enantiomeric separation of clenbuterol as analytical strategy to distinguish abuse from meat contamination. In: Recent Advances in Dope Analysis. Schänzer W, Geyer H, Gotzmann A, Mareck U (Eds.). Sportverlag Strauß, Cologne, Germany (2013).
16
Chou TQ. The preparation and properties of ephedrine and its salts. J. Biol. Chem. 70(1), 109–114 (1926).
17
Schwaninger AE, Meyer MR, Barnes AJ et al. Stereoselective urinary MDMA (ecstasy) and metabolites excretion kinetics following controlled MDMA administration to humans. Biochem. Pharmacol. 83(1), 131–138 (2012).
18
Jantos R, Skopp G. Postmortem blood and tissue concentrations of R- and S-enantiomers of methadone and its metabolite EDDP. Forensic Sci. Int. 226(1–3), 254–260 (2013).
19
Yamamoto T, Ohtani S. Estimation of chronological age from the racemization rate of L- and D-aspartic acid: how to completely separate enantiomers from dentin. Methods Mol. Biol. 794, 265–272 (2012).
20
Jones MD, Rainville PD, Isaac G, Wilson ID, Smith NW, Plumb RS. Ultra high resolution SFC–MS as a high throughput platform for metabolic phenotyping: application to metabolic profiling of rat and dog bile. J. Chromatogr. B Biomed. Sci. Appl. 966, 200–207 (2014).
future science group
