Analyst View Article Online
Published on 28 November 2013. Downloaded by Michigan Technological University on 19/10/2014 06:05:56.
PAPER
Cite this: Analyst, 2014, 139, 633
View Journal | View Issue
Detection of drugs in lifted cyanoacrylatedeveloped latent fingermarks using two laser desorption/ionisation mass spectrometric methods Latha Sundara and Frederick Rowell*ab This paper describes a method for lifting cyanoacrylate (CNA)-developed latent fingermarks from a glass surface and the detection of five drugs in lifted marks from fingers that had been in contact with the drugs, using Surface Assisted Laser Desorption Ionisation Time of Flight Mass Spectrometry (SALDI-TOFMS) or Matrix Assisted Laser Desorption Ionisation TOF-MS (MALDI-TOF-MS). Two drugs of abuse (cocaine and methadone) and three therapeutic drugs (aspirin, paracetamol and caffeine) were used as contact residues. Latent fingermarks spiked with the drugs were subjected to CNA fuming followed by dusting with ARRO SupraNano™ MS black magnetic powder (SALDI-TOF-MS) or 2,5-dihydroxybenzoic acid (DHB) (MALDI-TOF-MS). The dusted mark was then exposed to solvent vapour before lifting with a commercial fingerprint lifting tape following established procedures. The presence of the drugs was then confirmed by direct analysis on the tape without further processing using SALDI- or MALDI-TOF-MS. The black magnetic fingerprint powder provided visual enhancement of the CNA-fingermark while no
Received 14th May 2013 Accepted 28th November 2013
visual enhancement was observed for marks dusted with DHB powder. Similar [M + H]+ peaks for all the drug analytes were observed for both methods along with some sodium and potassium adducts for SALDI-MS and some major fragment ions but the SALDI signals were generally more intense. Simple
DOI: 10.1039/c3an00969f
exposure to acetone vapour of the CNA-developed marks enabled their effective transfer onto the tape
www.rsc.org/analyst
which was crucial for subsequent MS detection of the analytes.
Introduction In recent years, a considerable amount of work has been done on analysis of chemical constituents present within the latent ngermark. The techniques vary from using labelled antibodies, analysing by Raman spectrometry and via GC-mass spectrometry.1–3 Mass spectrometric methods for direct analysis of latent ngermarks include those based on ambient atmospheric pressure ionisation such as desorption electrospray ionization (DESI)-MS4 and direct analysis in real time (DART).5 Use of laser desorption/ionisation MS under vacuum was rst described in 2005 for direct analysis of residues within latent ngermarks for matrix-assisted-(MALDI-) and surface assisted(SALDI-) time of ight laser desorption/ionisation (TOF-MS) methods.6 This described detection of both endogenous constituents and exogenous constituents such as squalene and drugs such as cocaine, nicotine and its metabolite cotinine. This was followed with a more details of analysis and imaging in latent ngermarks of drugs and their metabolites,7 for detection a
ArroSupraNano Ltd, INEX Business Support Facility, Newcastle upon Tyne, NE17RU, UK
b
School of Pharmacy, Health and Wellbeing, Physical Sciences Building, University of Sunderland, Sunderland SR1 3SD, UK. E-mail: [email protected]; Fax: +44 191 515 3405; Tel: +44 191 515 2000
This journal is © The Royal Society of Chemistry 2014
of nicotine in smokers,8,9 explosives5 and amino acids.10 This approach used chemically engineered silica particles embedded with carbon black as dusting agents to produce marks of high sensitivity and denition11 which also acted as ionisationenhancing agents on laser irradiation in SALDI-TOF-MS12 so that dusted marks could be analysed directly without further processing. An alternative approach to obtain well dened ridge patterns of latent ngermarks uses MALDI-TOF-MS to produce a pattern of the signal intensity of one or more endogenous13 or exogenous14 constituents within the mark. In both SALDI- and MALDI-TOF-MS methods, a key step is the successful liing of the mark from the surface so that it can be inserted into the mass spectrometer. This was rst described for analysis of drug contact residues by MALDI- and SALDI-MS using conductive adhesive tape and plastic adhesive tape of the type used at crime scenes6 and subsequent SALDI-7–10 and MALDI-15 TOF-MS investigations have used commercial liing tape for this purpose. Location of latent ngermarks at crime scenes is generally carried out by dusting suspicious objects with commercial ngerprint powders or by exposing them to cyanoacrylate vapour16,17 which can then be dusted to enhance their visual denition. Both these methods help to identify the donor of the ngermark by comparison of the ridge pattern of the Analyst, 2014, 139, 633–642 | 633
View Article Online
Published on 28 November 2013. Downloaded by Michigan Technological University on 19/10/2014 06:05:56.
Analyst
ngermarks in the crime scene investigations with databases or with those of suspects. However, chemical identication of these developed prints can give further additional information on the donor such as contact residues, smoking habits or use of drugs. Such data may be used to eliminate or identify potential suspects. Since 1980 development of latent ngermarks using cyanoacrylate polymerisation has become widely established. This generally produces developed marks with good denition suitable for identication of the donor. To date SALDI- and MALDITOF-MS have not been applied to analysis of chemicals within cyanoacrylate-developed marks since successful liing to transfer the lied mark from the surface into the mass spectrometer has not been possible. We now describe a simple method for liing such marks and illustrate how subsequent SALDI-TOF-MS or MALDI-TOF-MS can be used for identication of drugs directly on the lied mark without the need for any additional sample processing.
Experimental
Paper
ngermark deposition. Each donor was requested not to wash his/her hands for at least 30 minutes prior to donating the ngermarks and were asked not to wipe their ngers across their face or neck just prior to donating. To simulate normal hand manipulations, the donor was asked to rub their palms and ngers together for 5 times and then lay the prints on a clean glass slide prepared as described above. A total of 8 blank ngermarks were collected for further analysis. Once collected, the glass slide was le on a bench in a dust free environment for an hour aer which it was dusted with black powder or DHB, or developed by the cyanoacrylate fuming method then dusted as described below. As the commercially available DHB powder was not that ne, before dusting it was ground to a ne powder using a mortar and pestle and then applied using a squirrel hair brush. Another set of 2 ngermarks was deposited directly onto stainless steel MALDI target plates and aged and treated as before. This organic chemical matrix assisting agent was chosen since it is commonly used for analysis of small molecules such as drugs19 and its use has been described for MALDI-TOF-MS detection of drugs in latent ngermarks.6
Materials
Fingermark deposition: drug-spiked ngermarks
The drugs of abuse cocaine hydrochloride (51621) and methadone hydrochloride (M0267) were purchased from Sigma Aldrich, UK. For therapeutic drugs Anadin Extra tablets which contain aspirin (300 mg), paracetamol (200 mg) and caffeine (45 mg) were purchased from a local drug store (Boots, UK). MALDI matrix, 2,5 dihydroxy benzoic acid (DHB) (85707), and the small molecule calibrant compounds such as papaverine hydrochloride (P3510), cesium iodide (21004) and reserpine (83580) were purchased from Sigma Aldrich UK. The solvents acetone, dichloromethane, acetonitrile, ethanol and toluene were purchased from VWR International, UK. Superglue (Hilka brand) and double sided sticky tape were purchased from a local DIY store, UK. ARRO SupraNano™ MS black magnetic ngerprint powder (hereaer termed ‘MS black FP powder’) was obtained from ARRO SupraNano Ltd, UK. The ngerprinting accessories such as liing tape, squirrel hair brush and magnetic wand were purchased from CSI, UK. MALDI target plates (MTP 384 target plate ground steel BC # 28078) were purchased from Bruker Daltonik, Germany.
The procedure described above was followed except the ngermarks were spiked with the drugs. To simulate drug-handled ngermarks, about 1 mg of each drug of abuse (cocaine and methadone) was placed in a clean glass Petri dish of 4 cm diameter and mixed using a stainless steel spatula and the mixture was distributed over the Petri dish surface. For the therapeutic drugs, an Anadin tablet was crushed and ground using a mortar and pestle and about 1 mg of the powdered tablet was spread in another clean glass Petri dish. To simulate normal hand manipulations the tip of the middle nger and the index nger of the donor touched the mixture of drugs and then touched the thumb of that nger, the drugs on the ngertips were distributed over the surface of both ngers. Aer waiting for about 30 minutes, the ungroomed marks were deposited on a clean glass slide using these ngers. Additional ngermarks were obtained by repeating the process. One set of drug-spiked ngermarks was also deposited directly onto MALDI target plates. Cyanoacrylate fuming
Methods Fingermark development Scheme 1 gives the procedure followed for liing and analysis of a dusted ngermark with and without cyanoacrylate development. Fingermark deposition: blank ngermarks For all the studies, duplicate ngermarks from 2 different ngers of the same donor were collected on a clean glass slide of dimension 76 52 mm which had been washed with soapy water, rinsed with deionised water followed by wiping with ethanol and drying using a clean tissue paper prior to collection. HOSDB, UK standard protocol was followed18 for
634 | Analyst, 2014, 139, 633–642
A perspex chamber of dimensions 40 40 cm tted with a door as shown in Fig. 1 was used for this study. The chamber was placed in a fume hood for additional safety. The chamber was tted with one stainless steel wired shelf in the middle. A hot plate was placed on the oor of the chamber and was set to 40 C. A wide mouthed crystallising dish lled with 200 ml of water was heated on the hotplate. The door was closed and the chamber le to reach a humidity of 65–70% which took about 10 minutes. A tin foil boat was lled with about 2 ml of superglue was then placed on the hot plate. Glass slides with the deposited ngermarks were placed on an open bottomed glass slide rack. As soon as the superglue was placed on the hot plate, the rack was placed on the wired shelf immediately on top of the hot plate so that any vapours came into direct contact with the
This journal is © The Royal Society of Chemistry 2014
View Article Online
Published on 28 November 2013. Downloaded by Michigan Technological University on 19/10/2014 06:05:56.
Paper
Scheme 1
Analyst
Procedure followed for fingermark development.
glass slides. The door of the chamber was then closed. Aer 10 minutes, the marks were checked for development. In most cases, 9 out of 10 ngermarks were found to have developed within this time. Fingermarks which were not developed were le in the chamber for an additional time until they were well developed. The developed marks were used for further study. Dusting of ngermarks Two sets of ngermarks (blank, and drug-spiked), were obtained, one set on the glass slides and the other on the MALDI target plates both with and without cyanoacrylate development. In both cases the marks were dusted with MS black FP powder using a magnetic wand or with DHB using a squirrel hair brush. Solvent treatment prior to liing of CNA-developed marks Chamber used for developing fingermarks by cyanoacrylate fuming.
Fig. 1
This journal is © The Royal Society of Chemistry 2014
Attempts were made to li the dusted CNA-developed ngermarks from the glass surface using commercially available
Analyst, 2014, 139, 633–642 | 635
View Article Online
Published on 28 November 2013. Downloaded by Michigan Technological University on 19/10/2014 06:05:56.
Analyst
ngerprint liing tapes. However, the li was very poor with a small amount of the dusted black powder and the supercial layer of the polymer being transferred. Most of the ngermark with the polymeric layer was retained on the glass slide. Hence, attempts were made to render the surface polymer less rigid by exposing the dusted cyanoacrylate-developed prints to a variety of solvent vapours in order to assist the complete liing of the mark. A chamber similar to the Cyanoacrylate fuming chamber was used for the solvent treatment. In this case the temperature of the hot plate was set to 40 C and a water bath with 200 ml of water was heated for 20 minutes. Aer 10 minutes, the hot plate was switched off and a 100 ml beaker with 25 ml of solvent was placed in the water bath for 3 minutes. Aer 3 minutes, the open bottomed glass slide rack with the dusted CNA-developed ngermark-containing glass slides was placed on the top shelf of the chamber. Meanwhile, the liing tape was cut into 2 cm 3 cm rectangular strips and a double-sided tape of approximately same dimension or smaller was stuck to the non-adhesive side of the liing tape. The developed marks were allowed to stand in the solvent chamber for exactly 2 minutes aer which the liing tape was immediately applied on the ngermark with very gentle pressure on the tape using a thumb. The mark was lied from glass surface and stuck onto the MALDI target plate by peeling off the backing paper of the double sided tape. The solvents tested were water, acetone, acetonitrile, dichloromethane, ethanol and toluene.
Paper
SALDI imaging was carried out on the lied marks to determine the overall distribution of the drugs across the ngermark using the Ultraex III system at a raster width of 200 um and a laser repetition rate of 200 Hz. Although, the instrument laser focus width can be controlled down to 10 mm to give an image with highest pixel resolution, the present study was carried out in order to determine the drug distribution in a short duration of time since the ridge pattern had already been obtained during the CNA-powder development process. With a 200 mm raster width at a laser repetition of 200 Hz frequency, it took approximately 30 minutes to scan an area of 1 cm2 of ngermark. FlexImaging soware from Bruker Daltonik, Germany was used for performing imaging experiments. Photographing developed ngermarks A Nikon D3100, digital camera with Nikon tted lens was used to photograph the developed images of the ngermarks.
Results and discussion Cyanoacrylate fuming For cyanoacrylate (CNA) fuming, we observed well-dened prints with about 65–70% humidity. Fig. 2a shows an example of the prints developed by cyanoacrylate fuming at about 65%
M/SALDI-TOF-MS studies The un-lied marks on the MALDI target plate and the lied marks were analysed by an Ultraex III MALDI TOF MS/MS, Bruker Daltonics system in positive and negative ion reectron modes. The instrument is equipped with Smartbeam Nd:Yag laser with adjustable repetition rate of 1 to 200 Hz. Average spectra were acquired for each of the lied ngermark using a random walk raster randomly covering the area of the ngermark. An average of 2000 shots were collected for each sample at a laser repetition rate of 200 Hz over a 60 to 1000 mass range. For each lied ngermark at least 3 spectra were acquired and the analyte signal intensities averaged. The instrument was calibrated before the start of any analysis and aer every six samples analysed using the small mass calibration mixture. This was prepared by mixing 1 mg ml1 of papaverine prepared in methanol, 1 mg ml1 of reserpine in acetonitrile and 10 mg ml1 of caesium iodide in deionised water in the volume ratio of 1 : 1 : 2 respectively. 1 ml of this calibration mix was spotted on the MALDI target plate and allowed to air dry at room temperature. Calibrant was spotted at different places surrounding the ngermark. Before analysing the sample, the calibrant closest to the sample was selected and the instrument was calibrated before analysing the sample. In positive ion mode, the peaks for [Cs]+ at m/z 132.91, [papaverine + H]+ at m/z 340.15 and [Cs2I]+ at m/z 392.72 and [reduced reserpine + H]+ at m/z 607.27 were used for calibration. For negative mode calibration, the peaks for [I] at m/z 126.90, [CsI2] at m/z 386.71 and [Cs2I3] at m/z 646.52 were used.
636 | Analyst, 2014, 139, 633–642
Fig. 2 (a) Cyanoacrylate-developed fingermark using 65% humidity. (b) Ridge details of a cyanoacrylate developed fingermark using 65% humidity.
This journal is © The Royal Society of Chemistry 2014
View Article Online
Published on 28 November 2013. Downloaded by Michigan Technological University on 19/10/2014 06:05:56.
Paper
humidity. Though most of the literature16,17 suggests an optimum humidity of 80 to 85% to yield a well-dened development, we observed extensive superglue deposition on the background when the humidity was set to 80% obscuring the ngermark image. With about 65–70% humidity, only the marks were developed leaving a fairly clean background with very minimal deposition. Moreover, with high humidity conditions we were not able to get good ridge detail as the polymerisation of the ridges almost fused together leaving a thick polymeric layer. With approximately 65% humidity conditions, only the mark material from the ridges was coated with polymer leaving a clean background between the ridges as shown in Fig. 2b. Dusting of ngermarks Cyanoacrylate development of latent ngermarks is carried out to provide visual images of the marks. These are then generally further developed with black powders or uorescent dyes to enhance the print detail.18 In this study we used magnetic MS black FP powder as the dusting agent which enhanced the mark detail (Fig. 3a and b). For the CNA-developed prints dusted with white DHB powder using a conventional squirrel hair brush, no visual enhancement of contrast or denition was observed (Fig. 3c and d). Application of magnetic particles using a magnetic wand is very unlikely to transfer material from one mark to the next during successive coatings as only the magnetic material hanging from the magnet makes contact with each mark during
Fig. 3 Photograph of cyanoacrylate-developed fingermarks (a) prior to dusting (b) after dusting with MS black FP powder (c) prior to dusting (d) after dusting with DHB.
This journal is © The Royal Society of Chemistry 2014
Analyst
each dusting and excess is discarded aer each mark is processed prior to re-loading the wand with fresh powder. In contrast dry-coating using conventional brushes invariably results in the hairs of the brush making contact with the surface of the mark. Since the same brush is currently used in subsequent dustings it is possible that cross-contamination between marks could occur. Further work is necessary to ascertain if this happens particularly with marks containing high concentrations of contact residues such as drugs. Effect of water vapour and organic solvents on the liing of CNA-developed ngermarks As far as the authors are aware, there is no literature on the routine liing of the cyanoacrylate-developed marks onto commercial adhesive-backed liing tapes. We wished to extend our previous studies on direct SALDI- and MALDI-TOF-MS analysis of drugs in lied marks on liing tape6,7 to their analysis in lied cyanoacrylate-developed marks. Hence it was necessary to identify a method to li dusted CNA-developed marks. The rst approach was to li the dusted cyanoacrylate developed marks without any solvent pre-treatment. Visually, aer liing, the tape had black powder with the ngermark detail on it but the glass slide from which the li was taken still had the ngermark intact with the coating of the polymer layer as shown in the Fig. 4a. MS analysis of this lied mark showed no peaks for the drug analytes. Hence, further studies were undertaken to li completely or most of the cyanoacrylatedeveloped mark from the glass surface. The second attempt was made by exposing the dusted developed marks to high humidity conditions. The lied mark did not show any improvement although supercial wetting was seen on the dusted marks. Finally, the volatile organic solvents ethanol, acetone, dichloromethane (DCM), toluene and acetonitrile were used to expose the marks to the solvent vapour. With marks exposed to ethanol, toluene and acetonitrile, some improvement was seen visually when a section of the ngermark was lied leaving the major portion of the ngermark on the glass surface. An uneven distribution of the lied mark was seen and it was not consistent from one ngermark to another.
Fig. 4 Dusted and lifted CNA-developed fingermark on MALDI target
plate (a) without acetone pre-treatment and (b) with acetone pretreatment.
Analyst, 2014, 139, 633–642 | 637
View Article Online
Published on 28 November 2013. Downloaded by Michigan Technological University on 19/10/2014 06:05:56.
Analyst
With acetone, a drastic improvement was seen as shown in Fig. 4b where most of the ngermark was transferred from the glass slide to the liing tape. It is possible that the acetone vapour soens the polymer mesh on the ngermark's surface thereby enabling almost complete transfer of the mark together with the powder onto the liing tape. Among the solvents tried, DCM was by far the most efficient solvent for stripping the cyanoacrylate-developed marks from the surface. However, with this solvent the process was difficult to control so if the time or the temperature of the water bath varies from the optimum, there is chance of losing the ngermark completely from the surface. The other drawback of using DCM was that the transfer results were not consistent from one ngermark to another.
M/SALDI-TOF-MS studies MS of unlied marks. For dusted samples deposited directly onto the target plate, as was observed in previous studies6,7 spiked marks not exposed to CNA and dusted with MS black powder produced spectrums for each of the drugs. In contrast equivalent marks dusted with DHB produced no drug peaks. However following exposure to acetone vapour drug-derived peaks were observed. Fig. 5 gives a comparison of the MS spectrums both following exposure to acetone vapour for the therapeutic drugs (aspirin, paracetamol and caffeine) dusted with DHB (MALDI-MS) with those using MS black FP powder (SALDI-MS) both in positive ionisation mode. For paracetamol intense peaks were seen at m/z 152.06 for [M + H]+, at m/z 174.06 [M + Na]+, and at m/z 190.06 [M + K]+ due to the protonated, and sodium and potassium adducts respectively plus a peak at 109.06 which is probably due to the loss of –COCH3. For aspirin,
Paper
peaks at m/z 203.04 [M + Na]+, m/z 219.04 [M + K]+ and a fragment peak at m/z 137.04 were seen. For caffeine, only the [M + H]+ peak at m/z 195.08 was present. In negative ionisation mode only two peaks due to aspirin were seen due to the deprotonated molecular ion [M H] at 179.04 and an intense fragment ion peak at m/z 137.04 as shown in Fig. 6. Generally similar spectrums were observed for each of the ve drugs in the unlied spiked marks for SALDI-MS and MALDI-MS (Table 1). However, differences were seen in peak intensities with the SALDI-MS peaks being considerably more intense (5–200 times, average for 13 common peaks of 57 times) than the corresponding MALDI-MS peak as also shown in Table 1. These differences probably reect the different ionisation mechanisms at play on laser irradiation for the two types of enhancing agents used.12 Use of alternative SALDIand MALDI-TOF-MS enhancing agents could affect these relative intensities. SALDI-TOF-MS and MALDI-TOF-MS studies in positive ionisation mode were carried out on dusted lied blank and drugspiked ngermarks from glass slides which had been developed by cyanoacrylate fuming followed by acetone treatment. Fig. 7 shows the SALDI-TOF-MS spectrums for these ngermarks spiked with cocaine and methadone which are identical to those in un-lied marks on a metal MALDI target plate (7b) and those lied from a plate (7c). It should be noted that lied dusted CNA-treated marks only showed drug-derived peaks aer acetone treatment (7d and 7e). It is possible that the acetone deposited on the surface of the mark co-dissolves both mark residues and deposited DHB enabling their co-crystallisation whereas without acetone these complexes did not form which is required for effective MALDI-TOF-MS.19 No peaks due to the drugs were seen in the blank marks (7a).
Fig. 5 Positive ion MS spectrums for un-lifted Anadin tablet spiked fingermark dusted with DHB (bottom) and MS black FP powder (top) both exposed to acetone vapour, showing peaks for aspirin ([M + Na]+ at m/z 203.04, [M + K]+ at m/z 219.04 and a fragment at m/z 137.04), paracetamol ([M + H]+ at m/z 152.06, [M + Na]+ at m/z 174.06, [M + K]+ at m/z 190.06 and a fragment at m/z 109.06) and caffeine ([M + H]+ at m/z 195.08).
638 | Analyst, 2014, 139, 633–642
This journal is © The Royal Society of Chemistry 2014
View Article Online
Published on 28 November 2013. Downloaded by Michigan Technological University on 19/10/2014 06:05:56.
Paper
Analyst
Fig. 6 Negative ion spectrum for un-lifted Anadin tablet-spiked fingermark developed with CNA and dusted with MS black FP powder showing peaks for aspirin [M H] at m/z 179.04 and a fragment at m/z 137.04 following exposure to acetone vapour.
Similar results were obtained using MALDI-MS as shown in Table 2 which also shows the effectiveness of exposure to the solvents studied. In each case the signal to noise ratio (S/N) was
Table 1
greater than 6. It is clearly evident that with acetone pre-treatment, almost all the drug-derived peaks detected on un-lied marks were also seen on the lied CNA marks.
Peaks and their intensities of ions for CNA-developed unlifted fingermarks dusted with DHB and MS black FP powder DHB
MS black FP powder
Drug/analyte ions
m/za
Intensity
SD
% RSD
Intensity
Cocaine (303.16) [M + H]+ [M + Na]+ [M + K]+ Fragment
304.16 326.16 342.16 182.16
745 ND ND 433
82 — — 44
11 — — 9.8
5694 1052 2828 9614
Methadone (309.21) [M + H]+ [M + Na]+ [M + K]+ Fragment Fragment
310.21 332.21 348.21 105.21 265.21
220 119 ND 220 2313
19 12 — 19 201
8.7 8.7 — 8.5 8.7
Aspirin (180.04) [M H] [M + Na]+ [M + K]+ Fragment
179.04 203.04 219.04 137.04
ND 36 219 ND
— 6 40 —
Paracetamol (151.06) [M + H]+ [M + Na]+ [M + K]+ Fragment
152.06 174.06 190.06 109.06
147 182 491 68
195.08 217.08 233.08
23 ND ND
Caffeine (194.08) [M + H]+ [M + Na]+ [M + K]+ X a
SD
% RSD
227 43 116 375
4 4.1 4.1 3.9
2558 839 601 2558 10 622
491 169 126 489 2135
19.2 20.1 21 19.1 20.1
— 17.3 18.1 —
2701 7384 38 904 24 779
300 716 3929 2428
11.1 9.7 10.1 9.8
15 18 54 8
10.1 9.8 11 11.1
2502 12 165 49 075 1295
178 888 3288 919
7.1 7.3 6.7 7.1
3
13.2 — —
1205 ND ND
49 — —
4.1 — —
— —
m/z are theoretical monoisotopic values, SD – standard deviation (n ¼ 3) and RSD – relative standard deviation.
This journal is © The Royal Society of Chemistry 2014
Analyst, 2014, 139, 633–642 | 639
View Article Online
Published on 28 November 2013. Downloaded by Michigan Technological University on 19/10/2014 06:05:56.
Analyst
Paper
SALDI-TOF-MS of latent fingermarks dusted with MS black FP showing peaks for cocaine and methadone. Bottom to top (a). Blank fingermark, (b) unlifted drug-spiked fingermark on metal target plate (c) lifted fingermark from target plate (d) lifted fingermark from a glass slide after cyanoacrylate development-without acetone treatment and (e) lifted fingermark from glass after cyanoacrylate development with acetone treatment. Major peaks for cocaine [M + H]+ at m/z 304.16, [M + Na]+ at m/z 326.16 and cocaine fragment at m/z 182.16. Major peaks for methadone [M + H]+ at m/z 310.21 and a methadone fragment at m/z 265.21. Fig. 7
The acetone exposure serves to loosen the CNA-developed mark aiding the liing process and to enable solubilisation and mixing of mark residues with the deposited DHB to achieve co-crystallisation. Since only passive vapour deposition occurs at the surface of the dusted mark this process differs from the active solvent spraying used during drywet activation of latent marks following dusting with the matrix assisting agent then wetting and MALDI-TOF-MS imaging.15 Peak intensities were lower in lied marks. This is not unexpected since only a fraction of the deposited drug is lied in the mark from the surface onto the liing tape. In an initial screen for the presence or absence of a drug within a complex MS spectrum, the presence of several analytespecic peaks can lead to a positive identication of the analyte's presence with a greater degree of certainty. This is
640 | Analyst, 2014, 139, 633–642
particularly true for MS of a latent ngermarks where a multitude of endogenous compounds of low molecular mass are also present and which may mask a single analyte peak. Interfering peaks from the SALDI particles may also be present but generally these are fewer than peaks resulting from organic matrix enhancing chemicals such as DHB.19 This is illustrated for cocaine where a peak due to an endogenous print constituent is observed around m/z of 304.40 very close to cocaine peak at m/z 304.16 as shown in Fig. 7a and b. The identication of the presence of cocaine in a screen can be assisted by the presence of a fragmentation peak at m/z 182.16 which is absent in the blank. Following initial identication, full conrmation can be obtained using MS/MS. It should be noted that all the above studies were performed with ungroomed and not natural latent marks and it is possible
This journal is © The Royal Society of Chemistry 2014
View Article Online
Paper
Analyst
Published on 28 November 2013. Downloaded by Michigan Technological University on 19/10/2014 06:05:56.
Table 2 M/SALDI-MS peaks observed for dusted and lifted drug-spiked fingermark developed by cyanoacrylate fuming followed by solvent treatment (S/N > 6)a
Drug/analyte ions
m/z
Water
Ethanol
Acetonitrile
Acetone
Dichloromethane (DCM)
Toluene
Cocaine (303.16) [M + H]+ [M + Na]+ [M + K]+ Fragment
304.16 326.16 342.26 182.16
ND ND ND Det
ND ND ND Det
ND Det ND ND
Det Det ND Det
Det Det ND ND
ND Det ND ND
Methadone (309.21) [M + H]+ [M + Na]+ [M + K]+ Fragment
310.21 332.21 348.21 265.21
Det Det ND ND
ND ND ND ND
ND ND ND ND
Det ND Det Det
Det ND ND ND
ND ND ND ND
Aspirin (180.04) [M + H]+ [M + Na]+ [M + K]+
181.04 203.04 219.14
ND ND ND
ND ND ND
ND ND ND
ND Det Det
ND Det ND
ND ND ND
Paracetamol (151.06) [M + H]+ [M + Na]+ [M + K]+ Fragment
152.06 174.06 190.16 109.06
ND ND ND ND
ND ND ND ND
Det ND ND ND
Det Det Det Det
Det ND ND ND
ND ND ND ND
195.08 217.08 234.18
ND ND ND
ND ND ND
ND ND ND
Det ND Det
ND ND ND
Det ND ND
Caffeine (194.08) [M + H]+ [M + Na]+ [M + K]+ Fragment a
ND, not detected (S/N < 6), Det, detected (S/N > 6).
that this could affect the results. Further studies are required to investigate this possibility.
SALDI imaging Fig. 8a and b show the intensity mapping of the [M + H]+ of cocaine (a) and methadone (b) for the prints dusted with MS black FP powder. For all the ion species, the distribution of the drug was relatively even across the ngermark and it was found that highest intensity was seen around the lower portion of the ngermark which could be due to the excess pressure applied while laying the ngermark. Since drugs appear to be relatively evenly distributed over the mark's surface it should be possible to detect their presence using the random walk raster for laser irradiation protocol used in this study. This supposition is supported by the %RSD values for the peaks shown in Table 1 for both MS methods which are all less than 20.1% (mean % RSD of 11.2% for MALDI-MS and of 10.5% SALDI-MS). Due to the excellent denition obtained with the combination of CNAdevelopment and subsequent dusting with the commercial magnetic black powder it is not necessary to undertake lengthy high denition MS imaging. In practice for rapid detection of drugs in such lied marks, only rastering and analyte signal intensities as described would be used for rapid mass screening of samples. For positives, detailed imaging would then be
This journal is © The Royal Society of Chemistry 2014
Fig. 8
(a) Cocaine [M + H]+, m/z 304.16. (b) Methadone [M + H]+, m/z
310.21.
Analyst, 2014, 139, 633–642 | 641
View Article Online
Analyst
undertaken followed by MS and MS-MS analysis of both peaks and troughs.
Published on 28 November 2013. Downloaded by Michigan Technological University on 19/10/2014 06:05:56.
Conclusions CNA fuming is a widely used forensic tool for the development of latent ngermarks. Polymerisation of the cyanoacrylate monomer in vapour phase leads to the formation of a white polymeric layer on the latent ngermark making it visible.16,17 The resulting thick, rigid polymeric layer adhering to the substrate of the ngermark makes it challenging to li the developed prints without losing the integrity of the mark. We have shown that exposure of such CNA-developed prints to acetone vapour provides a simple and efficient way of liing the print from a glass surface with a commonly used commercial liing tape. Without the solvent treatment there was no or very poor physical transfer of the print to the liing tape. Dusting with a commercial black powder improves the visual denition of the CNA-developed print. We have also demonstrated that contact residues such as cocaine, methadone, caffeine, aspirin and paracetamol can be analysed using SALDI-TOF-MS and MALDI-TOF-MS in such lied prints which have been dusted with a commercial black powder or 2,5-dihydroxybenzoic acid respectively then subjected to acetone treatment. Without such dusting and solvent treatment direct MS analysis of these drugs in lied or un-lied prints was not possible. Both MS methods can be used for direct detection of these drug contact residues on the liing tape without the need for any additional processing of the marks.
References 1 R. Leggett, E. E. Lee-Smith, S. M. Jickells and D. A. Russell, Angew. Chem., Int. Ed., 2007, 46, 4100–4103. 2 J. S. Day, H. G. M. Edwards, S. A. Dobrowski and A. M. Voice, Spectrochim. Acta, Part A, 2004, 60, 1725–1730.
642 | Analyst, 2014, 139, 633–642
Paper
3 R. S. Croxton, M. G. Baron, D. Butler, T. Kent and V. G. Sears, Forensic Sci. Int., 2010, 199, 93–102. 4 D. R. Ifa, N. E. Manicke, A. L. Dill and R. G. Cooks, Science, 2008, 321, 805. 5 F. J. Rowell, J. Seviour, A. Y. Lim, C. G. Elumbaring-Salazar, J. Loke and J. Ma, Forensic Sci. Int., 2012, 221, 84–91. 6 F. J. Rowell and B. J. Theaker, Fingerprint Analysis using Mass Spectrometry, US Patent no. US 7,923,682, 2011. 7 F. J. Rowell, K. Hudson and J. Seviour, Analyst, 2009, 134, 701–707. 8 M. Benton, F. Rowell, L. Sundar and M. Jan, Surf. Interface Anal., 2009, 42, 372–385. 9 M. Benton, M. J. Chua, F. Gu, F. Rowell and J. Ma, Forensic Sci. Int., 2010, 200, 28–34. 10 A. Y. Lim, Z. Ma, J. Ma and F. Rowell, J. Chromatogr. B: Biomed. Sci. Appl., 2011, 879, 2244–2250. 11 B. J. Theaker, K. E. Hudson and F. J. Rowell, Forensic Sci. Int., 2008, 174, 26–34. 12 A. Y. Lim, F. Gu, Z. Ma, J. Ma and F. Rowell, Analyst, 2011, 136, 2775–2785. 13 R. Wolstenholme, R. Bradshaw, M. R. Clench and S. Francese, Rapid Commun. Mass Spectrom., 2009, 23, 3031–3039. 14 R. Bradshaw, R. Wolstenholme, R. Blackledge, M. R. Clench, L. Ferguson and S. Francese, Rapid Commun. Mass Spectrom., 2011, 25, 1–8. 15 L. Ferguson, R. Bradshaw, R. Wolstenholme, M. R. Clench and S. Francese, Anal. Chem., 2011, 83, 5585–5591. 16 F. G. Kendall, Ident. News, 1982, 27(5), 3–5. 17 M. Paine, H. L. Bandey, S. M. Bleay and H. Willson, Forensic Sci. Int., 2011, 212, 130–142. 18 V. Bowman, Fingerprint Development Handbook, Home Office Scientic Development Branch, UK, 2005, part C, p. 119. 19 G. McCombie and R. Knochenmuss, Anal. Chem., 2004, 76, 4990–4997.
This journal is © The Royal Society of Chemistry 2014
Published on 28 November 2013. Downloaded by Michigan Technological University on 19/10/2014 06:05:56.
PAPER
Cite this: Analyst, 2014, 139, 633
View Journal | View Issue
Detection of drugs in lifted cyanoacrylatedeveloped latent fingermarks using two laser desorption/ionisation mass spectrometric methods Latha Sundara and Frederick Rowell*ab This paper describes a method for lifting cyanoacrylate (CNA)-developed latent fingermarks from a glass surface and the detection of five drugs in lifted marks from fingers that had been in contact with the drugs, using Surface Assisted Laser Desorption Ionisation Time of Flight Mass Spectrometry (SALDI-TOFMS) or Matrix Assisted Laser Desorption Ionisation TOF-MS (MALDI-TOF-MS). Two drugs of abuse (cocaine and methadone) and three therapeutic drugs (aspirin, paracetamol and caffeine) were used as contact residues. Latent fingermarks spiked with the drugs were subjected to CNA fuming followed by dusting with ARRO SupraNano™ MS black magnetic powder (SALDI-TOF-MS) or 2,5-dihydroxybenzoic acid (DHB) (MALDI-TOF-MS). The dusted mark was then exposed to solvent vapour before lifting with a commercial fingerprint lifting tape following established procedures. The presence of the drugs was then confirmed by direct analysis on the tape without further processing using SALDI- or MALDI-TOF-MS. The black magnetic fingerprint powder provided visual enhancement of the CNA-fingermark while no
Received 14th May 2013 Accepted 28th November 2013
visual enhancement was observed for marks dusted with DHB powder. Similar [M + H]+ peaks for all the drug analytes were observed for both methods along with some sodium and potassium adducts for SALDI-MS and some major fragment ions but the SALDI signals were generally more intense. Simple
DOI: 10.1039/c3an00969f
exposure to acetone vapour of the CNA-developed marks enabled their effective transfer onto the tape
www.rsc.org/analyst
which was crucial for subsequent MS detection of the analytes.
Introduction In recent years, a considerable amount of work has been done on analysis of chemical constituents present within the latent ngermark. The techniques vary from using labelled antibodies, analysing by Raman spectrometry and via GC-mass spectrometry.1–3 Mass spectrometric methods for direct analysis of latent ngermarks include those based on ambient atmospheric pressure ionisation such as desorption electrospray ionization (DESI)-MS4 and direct analysis in real time (DART).5 Use of laser desorption/ionisation MS under vacuum was rst described in 2005 for direct analysis of residues within latent ngermarks for matrix-assisted-(MALDI-) and surface assisted(SALDI-) time of ight laser desorption/ionisation (TOF-MS) methods.6 This described detection of both endogenous constituents and exogenous constituents such as squalene and drugs such as cocaine, nicotine and its metabolite cotinine. This was followed with a more details of analysis and imaging in latent ngermarks of drugs and their metabolites,7 for detection a
ArroSupraNano Ltd, INEX Business Support Facility, Newcastle upon Tyne, NE17RU, UK
b
School of Pharmacy, Health and Wellbeing, Physical Sciences Building, University of Sunderland, Sunderland SR1 3SD, UK. E-mail: [email protected]; Fax: +44 191 515 3405; Tel: +44 191 515 2000
This journal is © The Royal Society of Chemistry 2014
of nicotine in smokers,8,9 explosives5 and amino acids.10 This approach used chemically engineered silica particles embedded with carbon black as dusting agents to produce marks of high sensitivity and denition11 which also acted as ionisationenhancing agents on laser irradiation in SALDI-TOF-MS12 so that dusted marks could be analysed directly without further processing. An alternative approach to obtain well dened ridge patterns of latent ngermarks uses MALDI-TOF-MS to produce a pattern of the signal intensity of one or more endogenous13 or exogenous14 constituents within the mark. In both SALDI- and MALDI-TOF-MS methods, a key step is the successful liing of the mark from the surface so that it can be inserted into the mass spectrometer. This was rst described for analysis of drug contact residues by MALDI- and SALDI-MS using conductive adhesive tape and plastic adhesive tape of the type used at crime scenes6 and subsequent SALDI-7–10 and MALDI-15 TOF-MS investigations have used commercial liing tape for this purpose. Location of latent ngermarks at crime scenes is generally carried out by dusting suspicious objects with commercial ngerprint powders or by exposing them to cyanoacrylate vapour16,17 which can then be dusted to enhance their visual denition. Both these methods help to identify the donor of the ngermark by comparison of the ridge pattern of the Analyst, 2014, 139, 633–642 | 633
View Article Online
Published on 28 November 2013. Downloaded by Michigan Technological University on 19/10/2014 06:05:56.
Analyst
ngermarks in the crime scene investigations with databases or with those of suspects. However, chemical identication of these developed prints can give further additional information on the donor such as contact residues, smoking habits or use of drugs. Such data may be used to eliminate or identify potential suspects. Since 1980 development of latent ngermarks using cyanoacrylate polymerisation has become widely established. This generally produces developed marks with good denition suitable for identication of the donor. To date SALDI- and MALDITOF-MS have not been applied to analysis of chemicals within cyanoacrylate-developed marks since successful liing to transfer the lied mark from the surface into the mass spectrometer has not been possible. We now describe a simple method for liing such marks and illustrate how subsequent SALDI-TOF-MS or MALDI-TOF-MS can be used for identication of drugs directly on the lied mark without the need for any additional sample processing.
Experimental
Paper
ngermark deposition. Each donor was requested not to wash his/her hands for at least 30 minutes prior to donating the ngermarks and were asked not to wipe their ngers across their face or neck just prior to donating. To simulate normal hand manipulations, the donor was asked to rub their palms and ngers together for 5 times and then lay the prints on a clean glass slide prepared as described above. A total of 8 blank ngermarks were collected for further analysis. Once collected, the glass slide was le on a bench in a dust free environment for an hour aer which it was dusted with black powder or DHB, or developed by the cyanoacrylate fuming method then dusted as described below. As the commercially available DHB powder was not that ne, before dusting it was ground to a ne powder using a mortar and pestle and then applied using a squirrel hair brush. Another set of 2 ngermarks was deposited directly onto stainless steel MALDI target plates and aged and treated as before. This organic chemical matrix assisting agent was chosen since it is commonly used for analysis of small molecules such as drugs19 and its use has been described for MALDI-TOF-MS detection of drugs in latent ngermarks.6
Materials
Fingermark deposition: drug-spiked ngermarks
The drugs of abuse cocaine hydrochloride (51621) and methadone hydrochloride (M0267) were purchased from Sigma Aldrich, UK. For therapeutic drugs Anadin Extra tablets which contain aspirin (300 mg), paracetamol (200 mg) and caffeine (45 mg) were purchased from a local drug store (Boots, UK). MALDI matrix, 2,5 dihydroxy benzoic acid (DHB) (85707), and the small molecule calibrant compounds such as papaverine hydrochloride (P3510), cesium iodide (21004) and reserpine (83580) were purchased from Sigma Aldrich UK. The solvents acetone, dichloromethane, acetonitrile, ethanol and toluene were purchased from VWR International, UK. Superglue (Hilka brand) and double sided sticky tape were purchased from a local DIY store, UK. ARRO SupraNano™ MS black magnetic ngerprint powder (hereaer termed ‘MS black FP powder’) was obtained from ARRO SupraNano Ltd, UK. The ngerprinting accessories such as liing tape, squirrel hair brush and magnetic wand were purchased from CSI, UK. MALDI target plates (MTP 384 target plate ground steel BC # 28078) were purchased from Bruker Daltonik, Germany.
The procedure described above was followed except the ngermarks were spiked with the drugs. To simulate drug-handled ngermarks, about 1 mg of each drug of abuse (cocaine and methadone) was placed in a clean glass Petri dish of 4 cm diameter and mixed using a stainless steel spatula and the mixture was distributed over the Petri dish surface. For the therapeutic drugs, an Anadin tablet was crushed and ground using a mortar and pestle and about 1 mg of the powdered tablet was spread in another clean glass Petri dish. To simulate normal hand manipulations the tip of the middle nger and the index nger of the donor touched the mixture of drugs and then touched the thumb of that nger, the drugs on the ngertips were distributed over the surface of both ngers. Aer waiting for about 30 minutes, the ungroomed marks were deposited on a clean glass slide using these ngers. Additional ngermarks were obtained by repeating the process. One set of drug-spiked ngermarks was also deposited directly onto MALDI target plates. Cyanoacrylate fuming
Methods Fingermark development Scheme 1 gives the procedure followed for liing and analysis of a dusted ngermark with and without cyanoacrylate development. Fingermark deposition: blank ngermarks For all the studies, duplicate ngermarks from 2 different ngers of the same donor were collected on a clean glass slide of dimension 76 52 mm which had been washed with soapy water, rinsed with deionised water followed by wiping with ethanol and drying using a clean tissue paper prior to collection. HOSDB, UK standard protocol was followed18 for
634 | Analyst, 2014, 139, 633–642
A perspex chamber of dimensions 40 40 cm tted with a door as shown in Fig. 1 was used for this study. The chamber was placed in a fume hood for additional safety. The chamber was tted with one stainless steel wired shelf in the middle. A hot plate was placed on the oor of the chamber and was set to 40 C. A wide mouthed crystallising dish lled with 200 ml of water was heated on the hotplate. The door was closed and the chamber le to reach a humidity of 65–70% which took about 10 minutes. A tin foil boat was lled with about 2 ml of superglue was then placed on the hot plate. Glass slides with the deposited ngermarks were placed on an open bottomed glass slide rack. As soon as the superglue was placed on the hot plate, the rack was placed on the wired shelf immediately on top of the hot plate so that any vapours came into direct contact with the
This journal is © The Royal Society of Chemistry 2014
View Article Online
Published on 28 November 2013. Downloaded by Michigan Technological University on 19/10/2014 06:05:56.
Paper
Scheme 1
Analyst
Procedure followed for fingermark development.
glass slides. The door of the chamber was then closed. Aer 10 minutes, the marks were checked for development. In most cases, 9 out of 10 ngermarks were found to have developed within this time. Fingermarks which were not developed were le in the chamber for an additional time until they were well developed. The developed marks were used for further study. Dusting of ngermarks Two sets of ngermarks (blank, and drug-spiked), were obtained, one set on the glass slides and the other on the MALDI target plates both with and without cyanoacrylate development. In both cases the marks were dusted with MS black FP powder using a magnetic wand or with DHB using a squirrel hair brush. Solvent treatment prior to liing of CNA-developed marks Chamber used for developing fingermarks by cyanoacrylate fuming.
Fig. 1
This journal is © The Royal Society of Chemistry 2014
Attempts were made to li the dusted CNA-developed ngermarks from the glass surface using commercially available
Analyst, 2014, 139, 633–642 | 635
View Article Online
Published on 28 November 2013. Downloaded by Michigan Technological University on 19/10/2014 06:05:56.
Analyst
ngerprint liing tapes. However, the li was very poor with a small amount of the dusted black powder and the supercial layer of the polymer being transferred. Most of the ngermark with the polymeric layer was retained on the glass slide. Hence, attempts were made to render the surface polymer less rigid by exposing the dusted cyanoacrylate-developed prints to a variety of solvent vapours in order to assist the complete liing of the mark. A chamber similar to the Cyanoacrylate fuming chamber was used for the solvent treatment. In this case the temperature of the hot plate was set to 40 C and a water bath with 200 ml of water was heated for 20 minutes. Aer 10 minutes, the hot plate was switched off and a 100 ml beaker with 25 ml of solvent was placed in the water bath for 3 minutes. Aer 3 minutes, the open bottomed glass slide rack with the dusted CNA-developed ngermark-containing glass slides was placed on the top shelf of the chamber. Meanwhile, the liing tape was cut into 2 cm 3 cm rectangular strips and a double-sided tape of approximately same dimension or smaller was stuck to the non-adhesive side of the liing tape. The developed marks were allowed to stand in the solvent chamber for exactly 2 minutes aer which the liing tape was immediately applied on the ngermark with very gentle pressure on the tape using a thumb. The mark was lied from glass surface and stuck onto the MALDI target plate by peeling off the backing paper of the double sided tape. The solvents tested were water, acetone, acetonitrile, dichloromethane, ethanol and toluene.
Paper
SALDI imaging was carried out on the lied marks to determine the overall distribution of the drugs across the ngermark using the Ultraex III system at a raster width of 200 um and a laser repetition rate of 200 Hz. Although, the instrument laser focus width can be controlled down to 10 mm to give an image with highest pixel resolution, the present study was carried out in order to determine the drug distribution in a short duration of time since the ridge pattern had already been obtained during the CNA-powder development process. With a 200 mm raster width at a laser repetition of 200 Hz frequency, it took approximately 30 minutes to scan an area of 1 cm2 of ngermark. FlexImaging soware from Bruker Daltonik, Germany was used for performing imaging experiments. Photographing developed ngermarks A Nikon D3100, digital camera with Nikon tted lens was used to photograph the developed images of the ngermarks.
Results and discussion Cyanoacrylate fuming For cyanoacrylate (CNA) fuming, we observed well-dened prints with about 65–70% humidity. Fig. 2a shows an example of the prints developed by cyanoacrylate fuming at about 65%
M/SALDI-TOF-MS studies The un-lied marks on the MALDI target plate and the lied marks were analysed by an Ultraex III MALDI TOF MS/MS, Bruker Daltonics system in positive and negative ion reectron modes. The instrument is equipped with Smartbeam Nd:Yag laser with adjustable repetition rate of 1 to 200 Hz. Average spectra were acquired for each of the lied ngermark using a random walk raster randomly covering the area of the ngermark. An average of 2000 shots were collected for each sample at a laser repetition rate of 200 Hz over a 60 to 1000 mass range. For each lied ngermark at least 3 spectra were acquired and the analyte signal intensities averaged. The instrument was calibrated before the start of any analysis and aer every six samples analysed using the small mass calibration mixture. This was prepared by mixing 1 mg ml1 of papaverine prepared in methanol, 1 mg ml1 of reserpine in acetonitrile and 10 mg ml1 of caesium iodide in deionised water in the volume ratio of 1 : 1 : 2 respectively. 1 ml of this calibration mix was spotted on the MALDI target plate and allowed to air dry at room temperature. Calibrant was spotted at different places surrounding the ngermark. Before analysing the sample, the calibrant closest to the sample was selected and the instrument was calibrated before analysing the sample. In positive ion mode, the peaks for [Cs]+ at m/z 132.91, [papaverine + H]+ at m/z 340.15 and [Cs2I]+ at m/z 392.72 and [reduced reserpine + H]+ at m/z 607.27 were used for calibration. For negative mode calibration, the peaks for [I] at m/z 126.90, [CsI2] at m/z 386.71 and [Cs2I3] at m/z 646.52 were used.
636 | Analyst, 2014, 139, 633–642
Fig. 2 (a) Cyanoacrylate-developed fingermark using 65% humidity. (b) Ridge details of a cyanoacrylate developed fingermark using 65% humidity.
This journal is © The Royal Society of Chemistry 2014
View Article Online
Published on 28 November 2013. Downloaded by Michigan Technological University on 19/10/2014 06:05:56.
Paper
humidity. Though most of the literature16,17 suggests an optimum humidity of 80 to 85% to yield a well-dened development, we observed extensive superglue deposition on the background when the humidity was set to 80% obscuring the ngermark image. With about 65–70% humidity, only the marks were developed leaving a fairly clean background with very minimal deposition. Moreover, with high humidity conditions we were not able to get good ridge detail as the polymerisation of the ridges almost fused together leaving a thick polymeric layer. With approximately 65% humidity conditions, only the mark material from the ridges was coated with polymer leaving a clean background between the ridges as shown in Fig. 2b. Dusting of ngermarks Cyanoacrylate development of latent ngermarks is carried out to provide visual images of the marks. These are then generally further developed with black powders or uorescent dyes to enhance the print detail.18 In this study we used magnetic MS black FP powder as the dusting agent which enhanced the mark detail (Fig. 3a and b). For the CNA-developed prints dusted with white DHB powder using a conventional squirrel hair brush, no visual enhancement of contrast or denition was observed (Fig. 3c and d). Application of magnetic particles using a magnetic wand is very unlikely to transfer material from one mark to the next during successive coatings as only the magnetic material hanging from the magnet makes contact with each mark during
Fig. 3 Photograph of cyanoacrylate-developed fingermarks (a) prior to dusting (b) after dusting with MS black FP powder (c) prior to dusting (d) after dusting with DHB.
This journal is © The Royal Society of Chemistry 2014
Analyst
each dusting and excess is discarded aer each mark is processed prior to re-loading the wand with fresh powder. In contrast dry-coating using conventional brushes invariably results in the hairs of the brush making contact with the surface of the mark. Since the same brush is currently used in subsequent dustings it is possible that cross-contamination between marks could occur. Further work is necessary to ascertain if this happens particularly with marks containing high concentrations of contact residues such as drugs. Effect of water vapour and organic solvents on the liing of CNA-developed ngermarks As far as the authors are aware, there is no literature on the routine liing of the cyanoacrylate-developed marks onto commercial adhesive-backed liing tapes. We wished to extend our previous studies on direct SALDI- and MALDI-TOF-MS analysis of drugs in lied marks on liing tape6,7 to their analysis in lied cyanoacrylate-developed marks. Hence it was necessary to identify a method to li dusted CNA-developed marks. The rst approach was to li the dusted cyanoacrylate developed marks without any solvent pre-treatment. Visually, aer liing, the tape had black powder with the ngermark detail on it but the glass slide from which the li was taken still had the ngermark intact with the coating of the polymer layer as shown in the Fig. 4a. MS analysis of this lied mark showed no peaks for the drug analytes. Hence, further studies were undertaken to li completely or most of the cyanoacrylatedeveloped mark from the glass surface. The second attempt was made by exposing the dusted developed marks to high humidity conditions. The lied mark did not show any improvement although supercial wetting was seen on the dusted marks. Finally, the volatile organic solvents ethanol, acetone, dichloromethane (DCM), toluene and acetonitrile were used to expose the marks to the solvent vapour. With marks exposed to ethanol, toluene and acetonitrile, some improvement was seen visually when a section of the ngermark was lied leaving the major portion of the ngermark on the glass surface. An uneven distribution of the lied mark was seen and it was not consistent from one ngermark to another.
Fig. 4 Dusted and lifted CNA-developed fingermark on MALDI target
plate (a) without acetone pre-treatment and (b) with acetone pretreatment.
Analyst, 2014, 139, 633–642 | 637
View Article Online
Published on 28 November 2013. Downloaded by Michigan Technological University on 19/10/2014 06:05:56.
Analyst
With acetone, a drastic improvement was seen as shown in Fig. 4b where most of the ngermark was transferred from the glass slide to the liing tape. It is possible that the acetone vapour soens the polymer mesh on the ngermark's surface thereby enabling almost complete transfer of the mark together with the powder onto the liing tape. Among the solvents tried, DCM was by far the most efficient solvent for stripping the cyanoacrylate-developed marks from the surface. However, with this solvent the process was difficult to control so if the time or the temperature of the water bath varies from the optimum, there is chance of losing the ngermark completely from the surface. The other drawback of using DCM was that the transfer results were not consistent from one ngermark to another.
M/SALDI-TOF-MS studies MS of unlied marks. For dusted samples deposited directly onto the target plate, as was observed in previous studies6,7 spiked marks not exposed to CNA and dusted with MS black powder produced spectrums for each of the drugs. In contrast equivalent marks dusted with DHB produced no drug peaks. However following exposure to acetone vapour drug-derived peaks were observed. Fig. 5 gives a comparison of the MS spectrums both following exposure to acetone vapour for the therapeutic drugs (aspirin, paracetamol and caffeine) dusted with DHB (MALDI-MS) with those using MS black FP powder (SALDI-MS) both in positive ionisation mode. For paracetamol intense peaks were seen at m/z 152.06 for [M + H]+, at m/z 174.06 [M + Na]+, and at m/z 190.06 [M + K]+ due to the protonated, and sodium and potassium adducts respectively plus a peak at 109.06 which is probably due to the loss of –COCH3. For aspirin,
Paper
peaks at m/z 203.04 [M + Na]+, m/z 219.04 [M + K]+ and a fragment peak at m/z 137.04 were seen. For caffeine, only the [M + H]+ peak at m/z 195.08 was present. In negative ionisation mode only two peaks due to aspirin were seen due to the deprotonated molecular ion [M H] at 179.04 and an intense fragment ion peak at m/z 137.04 as shown in Fig. 6. Generally similar spectrums were observed for each of the ve drugs in the unlied spiked marks for SALDI-MS and MALDI-MS (Table 1). However, differences were seen in peak intensities with the SALDI-MS peaks being considerably more intense (5–200 times, average for 13 common peaks of 57 times) than the corresponding MALDI-MS peak as also shown in Table 1. These differences probably reect the different ionisation mechanisms at play on laser irradiation for the two types of enhancing agents used.12 Use of alternative SALDIand MALDI-TOF-MS enhancing agents could affect these relative intensities. SALDI-TOF-MS and MALDI-TOF-MS studies in positive ionisation mode were carried out on dusted lied blank and drugspiked ngermarks from glass slides which had been developed by cyanoacrylate fuming followed by acetone treatment. Fig. 7 shows the SALDI-TOF-MS spectrums for these ngermarks spiked with cocaine and methadone which are identical to those in un-lied marks on a metal MALDI target plate (7b) and those lied from a plate (7c). It should be noted that lied dusted CNA-treated marks only showed drug-derived peaks aer acetone treatment (7d and 7e). It is possible that the acetone deposited on the surface of the mark co-dissolves both mark residues and deposited DHB enabling their co-crystallisation whereas without acetone these complexes did not form which is required for effective MALDI-TOF-MS.19 No peaks due to the drugs were seen in the blank marks (7a).
Fig. 5 Positive ion MS spectrums for un-lifted Anadin tablet spiked fingermark dusted with DHB (bottom) and MS black FP powder (top) both exposed to acetone vapour, showing peaks for aspirin ([M + Na]+ at m/z 203.04, [M + K]+ at m/z 219.04 and a fragment at m/z 137.04), paracetamol ([M + H]+ at m/z 152.06, [M + Na]+ at m/z 174.06, [M + K]+ at m/z 190.06 and a fragment at m/z 109.06) and caffeine ([M + H]+ at m/z 195.08).
638 | Analyst, 2014, 139, 633–642
This journal is © The Royal Society of Chemistry 2014
View Article Online
Published on 28 November 2013. Downloaded by Michigan Technological University on 19/10/2014 06:05:56.
Paper
Analyst
Fig. 6 Negative ion spectrum for un-lifted Anadin tablet-spiked fingermark developed with CNA and dusted with MS black FP powder showing peaks for aspirin [M H] at m/z 179.04 and a fragment at m/z 137.04 following exposure to acetone vapour.
Similar results were obtained using MALDI-MS as shown in Table 2 which also shows the effectiveness of exposure to the solvents studied. In each case the signal to noise ratio (S/N) was
Table 1
greater than 6. It is clearly evident that with acetone pre-treatment, almost all the drug-derived peaks detected on un-lied marks were also seen on the lied CNA marks.
Peaks and their intensities of ions for CNA-developed unlifted fingermarks dusted with DHB and MS black FP powder DHB
MS black FP powder
Drug/analyte ions
m/za
Intensity
SD
% RSD
Intensity
Cocaine (303.16) [M + H]+ [M + Na]+ [M + K]+ Fragment
304.16 326.16 342.16 182.16
745 ND ND 433
82 — — 44
11 — — 9.8
5694 1052 2828 9614
Methadone (309.21) [M + H]+ [M + Na]+ [M + K]+ Fragment Fragment
310.21 332.21 348.21 105.21 265.21
220 119 ND 220 2313
19 12 — 19 201
8.7 8.7 — 8.5 8.7
Aspirin (180.04) [M H] [M + Na]+ [M + K]+ Fragment
179.04 203.04 219.04 137.04
ND 36 219 ND
— 6 40 —
Paracetamol (151.06) [M + H]+ [M + Na]+ [M + K]+ Fragment
152.06 174.06 190.06 109.06
147 182 491 68
195.08 217.08 233.08
23 ND ND
Caffeine (194.08) [M + H]+ [M + Na]+ [M + K]+ X a
SD
% RSD
227 43 116 375
4 4.1 4.1 3.9
2558 839 601 2558 10 622
491 169 126 489 2135
19.2 20.1 21 19.1 20.1
— 17.3 18.1 —
2701 7384 38 904 24 779
300 716 3929 2428
11.1 9.7 10.1 9.8
15 18 54 8
10.1 9.8 11 11.1
2502 12 165 49 075 1295
178 888 3288 919
7.1 7.3 6.7 7.1
3
13.2 — —
1205 ND ND
49 — —
4.1 — —
— —
m/z are theoretical monoisotopic values, SD – standard deviation (n ¼ 3) and RSD – relative standard deviation.
This journal is © The Royal Society of Chemistry 2014
Analyst, 2014, 139, 633–642 | 639
View Article Online
Published on 28 November 2013. Downloaded by Michigan Technological University on 19/10/2014 06:05:56.
Analyst
Paper
SALDI-TOF-MS of latent fingermarks dusted with MS black FP showing peaks for cocaine and methadone. Bottom to top (a). Blank fingermark, (b) unlifted drug-spiked fingermark on metal target plate (c) lifted fingermark from target plate (d) lifted fingermark from a glass slide after cyanoacrylate development-without acetone treatment and (e) lifted fingermark from glass after cyanoacrylate development with acetone treatment. Major peaks for cocaine [M + H]+ at m/z 304.16, [M + Na]+ at m/z 326.16 and cocaine fragment at m/z 182.16. Major peaks for methadone [M + H]+ at m/z 310.21 and a methadone fragment at m/z 265.21. Fig. 7
The acetone exposure serves to loosen the CNA-developed mark aiding the liing process and to enable solubilisation and mixing of mark residues with the deposited DHB to achieve co-crystallisation. Since only passive vapour deposition occurs at the surface of the dusted mark this process differs from the active solvent spraying used during drywet activation of latent marks following dusting with the matrix assisting agent then wetting and MALDI-TOF-MS imaging.15 Peak intensities were lower in lied marks. This is not unexpected since only a fraction of the deposited drug is lied in the mark from the surface onto the liing tape. In an initial screen for the presence or absence of a drug within a complex MS spectrum, the presence of several analytespecic peaks can lead to a positive identication of the analyte's presence with a greater degree of certainty. This is
640 | Analyst, 2014, 139, 633–642
particularly true for MS of a latent ngermarks where a multitude of endogenous compounds of low molecular mass are also present and which may mask a single analyte peak. Interfering peaks from the SALDI particles may also be present but generally these are fewer than peaks resulting from organic matrix enhancing chemicals such as DHB.19 This is illustrated for cocaine where a peak due to an endogenous print constituent is observed around m/z of 304.40 very close to cocaine peak at m/z 304.16 as shown in Fig. 7a and b. The identication of the presence of cocaine in a screen can be assisted by the presence of a fragmentation peak at m/z 182.16 which is absent in the blank. Following initial identication, full conrmation can be obtained using MS/MS. It should be noted that all the above studies were performed with ungroomed and not natural latent marks and it is possible
This journal is © The Royal Society of Chemistry 2014
View Article Online
Paper
Analyst
Published on 28 November 2013. Downloaded by Michigan Technological University on 19/10/2014 06:05:56.
Table 2 M/SALDI-MS peaks observed for dusted and lifted drug-spiked fingermark developed by cyanoacrylate fuming followed by solvent treatment (S/N > 6)a
Drug/analyte ions
m/z
Water
Ethanol
Acetonitrile
Acetone
Dichloromethane (DCM)
Toluene
Cocaine (303.16) [M + H]+ [M + Na]+ [M + K]+ Fragment
304.16 326.16 342.26 182.16
ND ND ND Det
ND ND ND Det
ND Det ND ND
Det Det ND Det
Det Det ND ND
ND Det ND ND
Methadone (309.21) [M + H]+ [M + Na]+ [M + K]+ Fragment
310.21 332.21 348.21 265.21
Det Det ND ND
ND ND ND ND
ND ND ND ND
Det ND Det Det
Det ND ND ND
ND ND ND ND
Aspirin (180.04) [M + H]+ [M + Na]+ [M + K]+
181.04 203.04 219.14
ND ND ND
ND ND ND
ND ND ND
ND Det Det
ND Det ND
ND ND ND
Paracetamol (151.06) [M + H]+ [M + Na]+ [M + K]+ Fragment
152.06 174.06 190.16 109.06
ND ND ND ND
ND ND ND ND
Det ND ND ND
Det Det Det Det
Det ND ND ND
ND ND ND ND
195.08 217.08 234.18
ND ND ND
ND ND ND
ND ND ND
Det ND Det
ND ND ND
Det ND ND
Caffeine (194.08) [M + H]+ [M + Na]+ [M + K]+ Fragment a
ND, not detected (S/N < 6), Det, detected (S/N > 6).
that this could affect the results. Further studies are required to investigate this possibility.
SALDI imaging Fig. 8a and b show the intensity mapping of the [M + H]+ of cocaine (a) and methadone (b) for the prints dusted with MS black FP powder. For all the ion species, the distribution of the drug was relatively even across the ngermark and it was found that highest intensity was seen around the lower portion of the ngermark which could be due to the excess pressure applied while laying the ngermark. Since drugs appear to be relatively evenly distributed over the mark's surface it should be possible to detect their presence using the random walk raster for laser irradiation protocol used in this study. This supposition is supported by the %RSD values for the peaks shown in Table 1 for both MS methods which are all less than 20.1% (mean % RSD of 11.2% for MALDI-MS and of 10.5% SALDI-MS). Due to the excellent denition obtained with the combination of CNAdevelopment and subsequent dusting with the commercial magnetic black powder it is not necessary to undertake lengthy high denition MS imaging. In practice for rapid detection of drugs in such lied marks, only rastering and analyte signal intensities as described would be used for rapid mass screening of samples. For positives, detailed imaging would then be
This journal is © The Royal Society of Chemistry 2014
Fig. 8
(a) Cocaine [M + H]+, m/z 304.16. (b) Methadone [M + H]+, m/z
310.21.
Analyst, 2014, 139, 633–642 | 641
View Article Online
Analyst
undertaken followed by MS and MS-MS analysis of both peaks and troughs.
Published on 28 November 2013. Downloaded by Michigan Technological University on 19/10/2014 06:05:56.
Conclusions CNA fuming is a widely used forensic tool for the development of latent ngermarks. Polymerisation of the cyanoacrylate monomer in vapour phase leads to the formation of a white polymeric layer on the latent ngermark making it visible.16,17 The resulting thick, rigid polymeric layer adhering to the substrate of the ngermark makes it challenging to li the developed prints without losing the integrity of the mark. We have shown that exposure of such CNA-developed prints to acetone vapour provides a simple and efficient way of liing the print from a glass surface with a commonly used commercial liing tape. Without the solvent treatment there was no or very poor physical transfer of the print to the liing tape. Dusting with a commercial black powder improves the visual denition of the CNA-developed print. We have also demonstrated that contact residues such as cocaine, methadone, caffeine, aspirin and paracetamol can be analysed using SALDI-TOF-MS and MALDI-TOF-MS in such lied prints which have been dusted with a commercial black powder or 2,5-dihydroxybenzoic acid respectively then subjected to acetone treatment. Without such dusting and solvent treatment direct MS analysis of these drugs in lied or un-lied prints was not possible. Both MS methods can be used for direct detection of these drug contact residues on the liing tape without the need for any additional processing of the marks.
References 1 R. Leggett, E. E. Lee-Smith, S. M. Jickells and D. A. Russell, Angew. Chem., Int. Ed., 2007, 46, 4100–4103. 2 J. S. Day, H. G. M. Edwards, S. A. Dobrowski and A. M. Voice, Spectrochim. Acta, Part A, 2004, 60, 1725–1730.
642 | Analyst, 2014, 139, 633–642
Paper
3 R. S. Croxton, M. G. Baron, D. Butler, T. Kent and V. G. Sears, Forensic Sci. Int., 2010, 199, 93–102. 4 D. R. Ifa, N. E. Manicke, A. L. Dill and R. G. Cooks, Science, 2008, 321, 805. 5 F. J. Rowell, J. Seviour, A. Y. Lim, C. G. Elumbaring-Salazar, J. Loke and J. Ma, Forensic Sci. Int., 2012, 221, 84–91. 6 F. J. Rowell and B. J. Theaker, Fingerprint Analysis using Mass Spectrometry, US Patent no. US 7,923,682, 2011. 7 F. J. Rowell, K. Hudson and J. Seviour, Analyst, 2009, 134, 701–707. 8 M. Benton, F. Rowell, L. Sundar and M. Jan, Surf. Interface Anal., 2009, 42, 372–385. 9 M. Benton, M. J. Chua, F. Gu, F. Rowell and J. Ma, Forensic Sci. Int., 2010, 200, 28–34. 10 A. Y. Lim, Z. Ma, J. Ma and F. Rowell, J. Chromatogr. B: Biomed. Sci. Appl., 2011, 879, 2244–2250. 11 B. J. Theaker, K. E. Hudson and F. J. Rowell, Forensic Sci. Int., 2008, 174, 26–34. 12 A. Y. Lim, F. Gu, Z. Ma, J. Ma and F. Rowell, Analyst, 2011, 136, 2775–2785. 13 R. Wolstenholme, R. Bradshaw, M. R. Clench and S. Francese, Rapid Commun. Mass Spectrom., 2009, 23, 3031–3039. 14 R. Bradshaw, R. Wolstenholme, R. Blackledge, M. R. Clench, L. Ferguson and S. Francese, Rapid Commun. Mass Spectrom., 2011, 25, 1–8. 15 L. Ferguson, R. Bradshaw, R. Wolstenholme, M. R. Clench and S. Francese, Anal. Chem., 2011, 83, 5585–5591. 16 F. G. Kendall, Ident. News, 1982, 27(5), 3–5. 17 M. Paine, H. L. Bandey, S. M. Bleay and H. Willson, Forensic Sci. Int., 2011, 212, 130–142. 18 V. Bowman, Fingerprint Development Handbook, Home Office Scientic Development Branch, UK, 2005, part C, p. 119. 19 G. McCombie and R. Knochenmuss, Anal. Chem., 2004, 76, 4990–4997.
This journal is © The Royal Society of Chemistry 2014
