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Research ArticleReceived: 28 February 2009 Revised: 24 July 2009 Accepted: 6 August 2009 Published online in Wiley Interscience: 6 October 2009

(www.interscience.wiley.com) DOI 10.1002/sia.3112

Direct detection of nicotine and cotininein dusted latent fingermarks of smokersby using hydrophobic silica particles and MSMatthew Benton,a∗ Frederick Rowell,b,c Latha Sundard and Ma Janc

Sub-micron sized hydrophobic silica particles doped with carbon black have been employed with latent fingermarks on glass andmetal surfaces to develop a simple method for detecting nicotine and cotinine using surface assisted laser desorption/ionisation-time of flight-mass spectrometry (SALDI-TOF-MS) in positive ion reflectron mode. Dusting of surfaces enables location of marksfor conventional identification of details but the particles also act as a laser desorption/ionisation enhancing agent (LDI)equivalent to a standard matrix enhancer 2,5-dihydroxybenzoic acid used in matrix assisted LDI-TOF-MS (MALDI-TOF-MS). Themethod has been applied in the analysis of smokers’ latent fingermarks on metal and glass surfaces. The metal surfaces wereanalysed following direct MS analysis of the pre-dusted prints, while the glass surfaces were analysed following lifting usingcommercial tape, and then MS analysis of these pre-dusted prints. In all cases of smokers, a major peak at m/z 163 (nicotine+1)and a less intense peak at m/z 161 (possibly anatabine+1) were found in the prints and in some cases additional peaks at177 (cotinine+1) and 199 (possibly cotinine+Na) were observed. The presence of nicotine and cotinine in smokers’ marks wasconfirmed using SALDI-TOF-MS-MS following high energy collision-induced dissociation when characteristic fragmentationpatterns were observed for each compound. Copyright c© 2009 John Wiley & Sons, Ltd.

Keywords: lifted latent fingermarks; hydrophobic silica particles; dusting agent; SALDI-TOF-MS; nicotine; cotinine; smokers; CID;fragmentation patterns

Introduction

There has been considerable, recent interest shown in obtaininginformation from latent fingermarks, in addition to the standardinformation derived from the associated visible patterns. This arisesas a considerable fraction of fingermarks found at a crime scene issmudged and the pattern is unclear, and if additional informationregarding the donor of the latent mark could be obtained byphysico-chemical analysis of the prints, it would be possible toestablish information as to the originator of the fingermark, or toprovide information that could link the print’s originator and asuspect.

The most powerful method for analysing the components ofa latent fingerprint is gas-chromatography-mass spectrometry(GC-MS). This enables analysis of the secreted constituents ofthe mark[1] or analysis of drugs and metabolites in sweat orsaliva.[2,3] Recently three new approaches have been describedfor the direct analysis of the constituents of fingermarks and ofcontact residues. The first employs attenuated total reflectionFT-IR spectroscopy/microscopy, which has been used to detectcontact residues of three drugs on the surface of a lifted mark[4]

and to produce an image of the distribution of endogenousconstituents within a fingermark.[5] The second method useselectrospray ionisation coupled with MS for direct analysis ofcontact residues, and to image their distribution within thesurface of the fingermark.[6] This has also been applied to liftedfingermarks but neither method has been applied in the detectionof nicotine or its metabolite cotinine in fingermarks from smokersand particularly those marks that have been pre-dusted withdeveloping powder, which is likely to be the case in majority offingermarks obtained at crime scenes.

The third is an antibody-based method for detecting cotininedeposited by smokers in latent fingermarks.[7] It involves useof mouse antibody-coated fluorescent nanoparticles and hencerequires a specific antibody raised to each analyte within themark to produce the required specificity. The method cannot beeasily used for latent fingermarks that are lifted from a crimescene and would be considered a presumptive method only, withconfirmation such as by GC-MS-MS still required if the results areto be used as forensic evidence.

We have reported that hydrophobic silica particles, which areincorporated within metals, metal oxides or carbon, can serveas agents for developing marks from surfaces by acting asmicro-particles for dusting, or as nanoparticles deposited fromsuspensions onto surfaces.[8] We have further demonstrated thatthese developed latent fingermarks can be subjected to surfaceassisted laser desorption/ionisation-time of flight-mass spectrom-

∗ Correspondence to: Matthew Benton, Nanofrontier Pte Ltd, ResearchTechnoPlaza, 50 Nanyang Drive, Singapore 637553, Singapore.E-mail: benton@ntu.edu.sg

a Nanofrontier Pte Ltd, Research TechnoPlaza, 50 Nanyang Drive, Singapore637553, Singapore

b ROAR Particles Ltd, Netpark Incubator, Sedgefield, County Durham, TS21 3FD,United Kingdom

c The School of Materials Science and Engineering, 50 Nanyang Avenue, NanyangTechnological University, Singapore 639798, Singapore

d ANT Nano PLC, Netpark Incubator, Sedgefield, County Durham, TS21 3FD,United Kingdom

Surf. Interface Anal. 2010, 42, 378–385 Copyright c© 2009 John Wiley & Sons, Ltd.

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Mass spectrometry of dusted latent fingermarks of smokers

etry (SALDI-TOF-MS) so that contact residues such as drugs ofabuse and their metabolites[9] or endogenous constituents offingermarks, such as squalene, can be directly detected.[10]

It is well established that nicotine adsorbed via cigarettesmoking is extensively metabolised to cotinine in vivo[11] and thereis evidence that both nicotine and cotinine are excreted together insweat.[2] This study aims to determine whether hydrophobic silicaparticles doped with carbon black can be used to detect nicotineand cotinine in pre-dusted latent fingermarks by SALDI-TOF-MSeither directly on a suitable surface or following lifting from thesurface. It further examines the potential of SALDI-TOF-MS-MS tounambiguously identify these compounds within such pre-dustedfingermarks using the fragmentation patterns produced from theircollision-induced dissociation (CID).

Methods

Chemicals and materials for dusting and lifting

Chemicals unless otherwise stated were from Sigma-Aldrich(Dorset, UK). The commercial matrix enhancer used was 2,5-dihydroxybenzoic acid (DHB) (10 mg ml−1 in 50 : 50 acetonitrile: deionised water [dH2O]). The fingerprinting/marking brushes,magnetic wands and commercial fingermark lifting tapes (productno. 96 110) were all purchased from Crime Scene InvestigationEquipment Ltd (formerly K9 Scenes of Crime Ltd; Northampton,UK). Double sided 3M 9713 conductive adhesive tape used wasfrom 3M (Singapore).

Synthesis of hydrophobic powder

The hydrophobic dusting agent used was the carbon black-incorporated agent which was prepared using carbon black andPTEOS (2 : 1) in the starting reagent mixture. The synthesis of whichis described in previous literature.[8] This was homogeneouslyincorporated into a mixture of fine iron particles (diameter<60 µm) and stearic acid (1.0% w/w) such that the ratio ofhydrophobic particles to iron particles was 2 : 98 w/w.

Fingermark MS analysis for nicotine and cotinine

Spiking of latent fingermarks

Ten volunteers who were non-smokers deposited their finger-marks by wiping unwashed forefingers across their eyebrows andthen touching either an unused glass microscope slide (SAIL Brand,China) or the surface of a stainless steel plate [96 or 384 well, KratosAxima matrix assisted LDI-TOF-MS (MALDI-TOF-MS) target plates].In order to ‘spike’ fingermarks from non-smokers, standards ofnicotine and cotinine (1 µl of 1 mg/ml in ethanol) were depositeddirectly onto the wells of another metal target plate and allowedto air dry and to these were applied the marks from donors. Stan-dard spectra were also obtained for nicotine and cotinine afterapplication of the standards directly to the surface of a secondtarget plate followed by addition of 1 µl of DHB [10 mg ml−1

in 50 : 50 acetonitrile to deionised water (dH2O)] to the air-driedspot. Following air drying, these standards were also subjected toMALDI-TOF-MS and MALDI-TOF-MS-MS as described below.

Dusting and lifting of prints

Latent marks from non-smokers (spiked and unspiked, n = 20) anda group of cigarette smokers (n = 20) were obtained as described

above. After ageing for 1 h under ambient conditions, the latentmarks were dusted with the magnetisable hydrophobic powderusing a commercial magnetic wand, and analysed by MS for markseither on the sample plate surface or following lifting of the markusing CSI fingerprint lifting tape or 3M 9713 conductive adhesivetape. The lifted marks were attached, print side up, onto the targetplates using strips of the adhesive tape.

Mass spectrometry of dusted marks

SALDI-TOF-MS and MALDI-TOF-MS were performed using aKratos Axima CFR Plus MALDI-TOF-MS or a Kratos Axima TOF2

(both supplied by Kratos, Shimadzu Biotech, Manchester, UK),operated in positive ion reflectron mode. MS were obtainedfor the m/z 40–700 region. For SALDI- and MALDI-TOF-MS-MS a Shimadzu Axima TOF2 instrument, equipped with acollision cell, was used. The peak of interest was fragmentedusing helium gas as the collision medium and laser fluenceof 103mJ/cm2. A total of 300 profiles were obtained for thespectrum, with each profile consisting of five shots. The instrumentwas calibrated using a mixture of reserpine, papaverine andCsI. Calibration was carried out separately for both MS andCID (MS/MS) experiments. In addition, for CID analyses, stearicacid was not used in the formulation of the hydrophobicparticles. Adhesive CSI fingerprint lifting tape, commonly usedduring police forensic investigations, was used for lifting dustedfingermarks. However, because the MALDI sample plate issubjected to high voltage during spectral acquisition, use ofan electrically conductive adhesive tape is recommended bythe manufacturer. Both the CSI and 3M 9713 tapes were usedsuccessfully in the SALDI-TOF analysis of lifted fingermarks.The peak intensity achieved by using the 3M tape was betterthan that of the CSI; however, the CSI tape gave a cleanerspectrum.

Imaging of distribution of nicotine and cotinine, within a latentfingermark

A fingermark taken from a smoker was deposited onto theMALDI plate surface as described above and then dusted withhydrophobic silica powder. Following SALDI-TOF-MS a 0.9 cm× 0.9 cm area intensity map was obtained using the softwarepackage provided by the manufacturer. The total ion count wasobtained over the m/z 50–1000 region and the relative intensitiesof the peaks at m/z 163 (nicotine) and 177 (cotinine) over this areawere determined. The corresponding pattern of distribution of acomponent within the hydrophobic particles with m/z 413 wasalso obtained on the same mark. The spacing between various laserfiring points in the raster pattern during an imaging experimentwas set to 100 µm, the same as the diameter of the laser. Theaverage ridge breadth of the hand is approximately 480 µm inyoung male adults, while on females they are slightly narrowerand smaller.[12]

Results

MS analysis of nicotine and cotinine in spiked latent finger-marks from non-smokers

As seen in Fig. 1, no peaks due to nicotine (FW 162) or cotinine(FW 176) are observed in the absence of a matrix enhancing agentfor a latent mark that is spiked with the mixture of nicotine and

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0

50

100

%Int. 7.9 mV 234 mV 402 mV 203 mV

150 155 160 165 170 175 180 185 190 195 200

Mass/Charge

3[c].

4[c].F5163.35 {r2535}

163.38 {r2682}157.14 {r2600}

151.21 {r2484}

157.26 {r2566} 180.28 {r2531} 188.34 {r2332}150.34 {r2336} 172.35 {r2341}

177.26 {r2571}155.26 {r2651} 193.23 {r2234}163.38 {r2714}

199.38 {r2471}

177.36 {r2835}171.32 {r2567}

151.22 {r2593}163.50 {r2848} 185.35 {r1894}177.50 {r2925} 194.39 {r2261}170.29 {r1926}157.33 {r1404}

a

d

c

b

1[c].F4

2[c].F4

60 laser_100ug_h12_wot_dustin_nicotine and cotinine_on_fingerprint_right0001, 60 laser_100ug_nicotine and cotinine_on_fingerprint_right0001, 60 laser_100ug_well5_nicotine and cotinine0001, 60 laser_b Kratos PCAxima CFRplus V2.4.1

Figure 1. MALDI- and SALDI-TOF-MS of latent fingermarks from a non-smoker on a stainless steel plate and spiked with 10 µl of a solution containinga 1 µg/ml mixture of nicotine (m/z 163) and cotinine (m/z 177). Bottom to top: a: spiked latent marks with no hydrophobic particles or DHB, b: spikedlatent marks treated with hydrophobic particles, c: spiked latent marks pre-dusted with DHB and d: unspiked latent mark pre-dusted with hydrophobicparticles.

0

10

20

30

40

50

60

70

80

90

100

%Int.

150 155 160 165 170 175 180 185 190 195 200

m/z

1[c].O15

167.81 {i4643}

150.84 {i10508}

151.82 {i8407}

179.82 {i6274}

153.86 {i2562} 191.84 {i2473}

183.85 {i1726}196.88 {i1356}166.77 {i1306} 185.93 {i1088}157.81 {i1057}

161.88 {i4599}

Figure 2. SALDI-MS of a non-smoker’s fingermark developed using hydrophobic powder and lifted using conductive adhesive tape. The peaks at m/z161, 163 177 and 199 are absent, while the peak present at m/z 151 is associated with the dusting agent. The origin of the other peaks in the spectrumhas not yet been identified.

cotinine [10 ng of each, Fig. 1(a)]. When the conventional matrixassisting agent DHB is added to marks that have been spikedwith 10 ng of each compound, then peaks at m/z 163 and 177are observed (Fig. 1(c)). When the hydrophobic dusting agent isadded to the spiked latent marks, peaks at m/z 163 and 177 areagain observed (Fig. 1(b)) indicating that this agent also acts as anenhancing agent. An additional peak at m/z 199 is now observedto be associated with the appearance of m/z 177 and is probablydue to the sodium adduct of cotinine. These observations areconfirmed by the MS of marks taken from non-smoking volunteers.

A typical SALDI-MS from the lifted dusted mark of a non-smokeris shown in Fig. 2 where no peak at m/z 163 (or 161, 177 or 199) isobserved.

MS analysis of nicotine and cotinine in latent fingermarks fromsmokers

In all cases for marks dusted with the hydrophobic powder andanalysed either directly on surfaces or following lifting, a peak atm/z 163 was observed. In addition a peak at m/z 161 was always

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Mass spectrometry of dusted latent fingermarks of smokers

0

20

40

60

80

100

%Int.

180 182 184 186 188 190 192 194 196 198 200 202 204

Mass/Charge

102 mV[sum= 10171 mV] Profiles 1-100 Smooth Av 5

Pepmix Ion Gate Setup

Data: dusting_mark_middle_fingerprint_D110001.F10 17 May 2006 13:41 Cal: small mols fri 24 Feb 2006 14:11Kratos PC Axima CFRplus V2.4.1: Mode reflectron, Power: 60, Blanked, P.Ext. @ 500 (bin 50)

180.08 {r2601}

182.17 {r2728}

192.08 {r2126}202.28 {r2341}199.16 {r2342}

188.12 {r2098}180.96 {r2679}200.29 {r2322}

186.28 {r2682}204.10 {r2287}180.21 {r2173} 184.26 {r2098} 196.94 {r1999}189.12 {r1775}

200.17 {r751}193.07 {r908} 203.27 {r748}

0

20

40

60

80

100

%Int.

156 158 160 162 164 166 168 170 172 174 176 178 180

Mass/Charge

348 mV[sum= 34832 mV] Profiles 1-100 Smooth Av 5

Pepmix Ion Gate Setup

Data: dusting_mark_middle_fingerprint_D110001.F10 17 May 2006 13:41 Cal: small mols fri 24 Feb 2006 14:11Kratos PC Axima CFRplus V2.4.1: Mode reflectron, Power: 60, Blanked, P.Ext. @ 500 (bin 50)

163.18 {r2698}

161.16 {r2638}

168.08 {r2429}172.27 {r2733}163.30 {r2814}

177.16 {r2318}167.00 {r2435}162.16 {r2345}156.08 {r2012}173.26 {r2123} 179.14 {r1256}170.09 {r799}

Figure 3. SALDI-TOF-MS of latent fingermark from a smoker (24 h since last cigarette) deposited on a stainless steel plate pre-dusted with hydrophobicparticles; upper m/z range 155–180, lower m/z range 180–205.

observed and peaks of lower intensity at m/z 177 and 199 wereoften observed. A typical SALDI spectrum is shown in Fig. 3 fora dusted mark on a metal target plate and in Fig. 4 for a lifteddusted mark.

CID spectra for nicotine and cotinine

CID of a nicotine standard and the corresponding peaks in a smoker

The CID-fragmentation spectrum for a nicotine standard from theMALDI-MS peak at m/z 163 is shown in Fig. 5 (upper spectrum)and that for the SALDI-MS peak from a smoker at m/z 163 is shownin the lower spectrum.

CID of a cotinine standard and the corresponding peak in a smoker

The CID-fragmentation spectrum for a cotinine standard from theMALDI-MS peak at m/z 177 is shown in Fig. 6 (upper spectrum)and that for the SALDI-MS peak from a smoker at m/z 177 is shownin the lower spectrum.

Imaging of distribution of nicotine and cotinine within a latentfingermark

The intensity map in Fig. 7 (top left) shows the specific distributionof nicotine over the area of the developed mark derived fromthe peak at m/z 163. The corresponding data for cotinine fromthe m/z 177 peak are shown in Fig. 7 (top right). In both casesthe ridge patterns can be discerned with areas of higher intensitylocated along the ridges. The bottom image is of an unidentifiedcomponent of m/z 413 that is present within the hydrophobicsilica particles. This shows a pattern of distribution that is similarto that of nicotine and cotinine.

Discussion

The results with standards and with ‘spiked’ fingermarks demon-strate that the hydrophobic silica particles perform as effectiveionisation/desorption agents for the analysis of both nicotine andcotinine, producing peaks associated with the [M+1]+ cationswhich have intensities at least equivalent to those obtained when

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0

10

20

30

40

50

60

70

80

90

100

%Int.

154 156 158 160 162 164 166 168 170 172 174 176 178 180

m/z

1[c].N3

163.10 {i12643}

162.06 {i5415}

180.08 {i2451}164.11 {i2357}168.04 {i1945}154.06 {i1907}

0

10

20

30

40

50

60

70

80

90

100

%Int.

178 180 182 184 186 188 190 192 194 196 198 200 202 204

m/z

1[c].N3

180.08 {i2451}

186.23 {i1547}

189.09 {i1121}

178.10 {i851} 197.14 {i710}

194.15 {i512}182.09 {i476} 198.27 {i442}187.13 {i438} 204.18 {i431}191.12 {i326}

184.73 {i251} 201.15 {i233}181.41 {i216} 195.67 {i168}

Figure 4. SALDI-MS of a smoker’s print showing nicotine at m/z 163. The print was dusted using hydrophobic silica powder and lifted with a conductiveadhesive tape.

the commonly used MALDI-TOF-MS matrix enhancing agent, DHB,is used with the same standards. Such enhancement is possiblydue to strong adsorption of the analytes onto these hydrophobicsilica particles, which are amorphous with a diameter of about300 nm,[8] coupled with their protonation at the surface duringlaser irradiation at 337 nm. We propose that the presence of em-bedded carbon black in the formulation plays a key role in thisionisation process (unpublished results).

The results from the initial spiking experiments clearly demon-strate that nicotine and cotinine applied to latent fingermarksfrom non-smokers can be easily detected by TOF-MS when amatrix enhancing chemical such as DHB is added or when thehydrophobic silica particles used to develop the latent marks arepresent (Fig. 1). Major peaks were found at m/z values of 163.3(formula weight for nicotine is 162.23), 177.3 (formula weight forcotinine is 176.22) and 199.2. This last peak is possibly due to thesodium adduct of cotinine (C10H12N2ONa, formula weight 199.21).These peaks are absent from the pre-dusted latent fingermarksof volunteers (Fig. 2) but the nicotine peak at m/z 163 is seen as

shown in Fig. 3 for a mark on a metal plate and in Fig. 4 for thedusted and lifted mark taken from smokers.

The SALDI-TOF dataset from a single smoker’s fingermarks(Chinese male, aged 25–30) was obtained from spectra at varioustime points, both within a day and over an 8-day period (14time points). The peak intensities of m/z 163 within these spectraappear to be reasonably consistent. In addition, there appears tobe variation in the m/z 163 peak intensity among different smokers(from a limited number of repeat experiments carried out) and thevalues of m/z 163 are in all but a few cases, significantly (threetimes that of the background signal) above those observed inSALDI-TOF spectra of non-smoker’s fingermarks. However, theredoes not seem to be a simple correlation between the numberof cigarettes consumed per day and nicotine peak intensity. Thesample population were mostly male donors (data not shown).Fingermarks from only one female smoker were obtained.

Fingermarks were obtained from donors after hand washingand air drying, in an attempt to obtain prints consisting ofmostly eccrine sweat, to compare with those consisting of

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0

20

40

60

80

100

%Int.

40 50 60 70 80 90 100 110 120 130 140 150

m/z

1[c].O5

2[c].O2

120.19 {i956}

83.81 {i567}

131.17{i8294}

131.10{i7308}132.26{i6585}

131.32 {i3750}

131.86 {i2852}

84.21{i2764}44.10 {i2025} 106.19 {i1871}84.28{i1600}

105.79 {i1215}

44.04 {i1147}

119.82 {i630}149.67 {i404}43.83 {i392} 134.88 {i381}

Figure 5. MALDI-MS-MS (upper) of a nicotine standard following CID of the m/z 163 peak. SALDI-MS-MS of the m/z 163 peak of spectra from a smoker’sprint following CID. This lower spectrum was obtained from a mark pre-dusted with hydrophobic silica particles, then lifted with a conductive adhesivetape prior to MS. The spectra are 0.4 amu different due to reduced TOF for the mark on the raised tape.

0

20

40

60

80

100

%Int.

40 50 60 70 80 90 100 110 120 130 140 150 160

Mass/Charge

1[c].1

2[c].1

4.1 mV 34 mV

146.23 {i3438}

80.23 {i1405}

98.24 {i1025}118.26 {i860}

147.73 {i583}120.26 {i419}

146.23 {i414}

149.15 {i218}

58.19 {i172}

80.21 {i161}98.24 {i142} 118.30 {i133}

162.90 {i113}

Figure 6. MALDI-MS-MS CID of a cotinine standard on the MALDI plate using DHB as matrix (upper) and SALDI-MS-MS CID for the peak at m/z 177 from asmoker (lower) also on a target plate.

sebaceous sweat obtained from the forehead. SALDI-TOF resultsshow strong m/z 163 peaks for these samples as comparedto spectra obtained from sebaceous marks (data not shown);however, more fingermarks need to be obtained in this mannerfor a full assessment of nicotine detection in different types ofsweat.

The results show that nicotine is a potential marker for indicatingthat the originator of the print was a smoker because the 163 amupeak is present in all spectra observed from smokers (n = 20)

and it is absent at equivalent high intensities in non-smokers(also n = 10). We have shown in a recent unpublished largerstudy that background nicotine may be present in the marks forsome non-smokers due to environmental contamination and/orcontact with smokers, and this will be described in a subsequentcommunication.

Confirmation of the presence of nicotine in the MS of developedmarks was achieved from the CID-fragmentation pattern which isidentical to that of a nicotine standard (Fig. 5). Similar confirmation

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Figure 7. Intensity map of 0.9 cm × 0.9 cm area of a smoker’s print showing the distribution and intensity of nicotine (m/z 163) (top left) and cotinine(m/z 177 ions) (top right). The bottom image is of the distribution and intensity of the m/z 413 peak over the surface. This is derived from a componentwithin the hydrophobic particles. The print was deposited on the MALDI plate and dusted with hydrophobic silica particles prior to SALDI-MS. Highintensity regions are in red and low intensity regions are in blue.

was achieved for cotinine (Fig. 6). This is an additional advantageof this method as MS-MS confirmation via CID is rapid and isaccepted for unambiguous confirmation of the identity of analytesin forensic samples. A minimum of four fragments of equivalentpeak intensities is generally required to confirm the identity of asubstance following CID, based on the EC guidelines for the useof identification points. As seen in Fig. 5, this applies to the CIDfor the nicotine peak at m/z 163 where fragments of m/z 131,120, 106, 84, 80 and 44 are seen both in the sample and thestandard.[13]

Other peaks commonly found in the MS of smokers but atlow intensity included those at m/z 177, which have been shownfrom CID fragmentation to be due to the presence of nicotinemetabolite cotinine and at m/z 199, which are probably due to thesodiated cation of cotinine as a peak at this value was observedin the fingermark spiked with cotinine and developed with thesame hydrophobic powder (Fig. 1(b)). CID-induced fragmentationof this m/z 199 peak only yielded a fragment at m/z 23 whichwould be expected for this compound (results not shown).Cationisation by metal ions is a common phenomenon in MALDI-TOF-MS.[14]

It should also be noted from spiked fingermarks seen inFig. 1 that both MALDI- and SALDI-MS produce peaks of higher

intensity for nicotine than for cotinine for standards of the sameconcentrations (10 ng of each in Fig. 1). The reduced MS sensitivityfor cotinine may explain the absence of m/z 177 peaks in somesmokers.

The interrogation of a dusted fingermark using SALDI-MSinvolves the thermal desorption of material from its surface,using the energy of the 337 nm laser. The process may causescattering of the dusting powder at a microscopic level; however,the process is not visibly destructive. The MS-scanning processmay be repeated many times without any visible changes tothe ridge integrity of the print or to the apparent quality ofthe SALDI-TOF spectrum. However, upon repeated scanningat the same spot on the sample, peaks for analytes such asnicotine will become progressively weaker as the chemical isdesorbed but the rastering process ensures that this does nothappen.

The presence of the peak at 161 amu is of interest as it isalso found together with nicotine in all smokers. It is known thatalthough nicotine constitutes about 95% of alkaloid content intobacco leaves, several other alkaloids are also present. Of thesenornicotine (RMM 148) and anatabine (RMM 160) are the mostabundant.[11] The peak at m/z 161 may be due to anatabine,however further work is needed to confirm this.

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The distribution of nicotine at m/z 163 and of cotinine atm/z 177 over the surface of a section of a dusted mark wasdetermined using the software package provided with the MSsystem. The resulting images are shown in Fig. 7 (upper left)for nicotine and in Fig. 7 (upper right) for cotinine. Both imagesindicate that these compounds are unevenly distributed alongthe ridges of the developed mark but are concentrated withinpockets which are probably associated with sweat pores onthe surface of the skin. The samples analysed in this mannerwere derived mainly by touching the sebum secretions from theforehead with a forefinger; hence the distribution pattern maymerely reflect the topography of the finger surface, althoughthe pattern observed resembles the image obtained for thedistribution of fluorescently labelled anti-cotinine antibodiesover the surface of a fingermark derived from sweat (eccrine)secretions.[7]

It is interesting to compare these similar patterns of distributionfor nicotine and cotinine with that obtained for the samefingermark from a component within the hydrophobic silicaparticles that are used to develop the latent marks (Fig. 7; lowerimage). This is again similar to the previous two images as would beexpected if the ionisation of constituents within the fingermarksdepends on their adsorption onto the particles with subsequentproton donation from the surface determinants of the particlesduring laser irradiation prior to desorption of the protonatedanalytes and their detection.

References

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[2] M. Heustis, J. Oyler, E. Cone, A. Wstadik, D. Schoendorfer, R. Joseph,J. Chromatogr. B. 1999, 733, 247.

[3] D. Kidwell, J. Holland, S. Athanaselis, J. Chromatogr. B. 1998, 713,111.

[4] C. Ricci, K. Chan, S. Kazarian, Appl. Spectrosc. 2006, 60, 1013.[5] C. Ricci, S. Bleay, S. Kazarian, Anal. Chem. 2007, 79, 5771.[6] D. Ifa, N. Manicke, A. Dill, R. Cooks, Science 2008, 321, 805.[7] E. Leggett, E. Lee-Smith, S. Jickells, D. Russell, Angew. Chem. Int. Ed.

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