Science and Justice 51 (2011) 196–203

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Ultra-trace analysis of illicit drugs from transfer of an electrostatic lift

Nicole Wallace, Edward Hueske, Guido F. Verbeck ⁎Department of Chemistry, University of North Texas, Denton, TX 76203, United States

⁎ Corresponding author. Tel.: +1 940 369 8423.E-mail address: gverbeck@unt.edu (G. Verbeck).

1355-0306/$ – see front matter © 2010 Forensic Sciencdoi:10.1016/j.scijus.2010.11.004

a b s t r a c t

a r t i c l e i n f o

Article history:Received 6 September 2010Received in revised form 19 October 2010Accepted 11 November 2010

Keywords:Electrostatic liftMass spectrometryNanosprayMicromanipulationIllicit drugs

This article introduces a method of collecting and analysing drug residues that integrates both electrostaticlifting and nanomanipulation-coupled to nanospray ionization mass spectrometry. The application of thishyphenated technique exhibits a useful means of collection and extraction of drug residues with ease andefficiency along with decreased limits of detection. From this method, it will be shown how increasedsensitivity of analysis and lower limits of detection for drug analysis can be achieved. The same principles thatallow lifting of dust prints by electrostatic lifting can be applied to lifting drug residues. Probing of the drugresidues by nanomanipulation occurs directly from the lift, which provides a great platform for extraction.Nanomanipulation-coupled to nanospray ionization-mass spectrometry has been used for the extraction oftrace analytes in previous experiments and is known as a very sensitive technique for the detection of ultra-trace residue. This method will demonstrate the electrostatic lifting of drug residue particles from a surfacefollowed by extraction and ionization with nanomanipulation-nanospray ionization. The utility of this novelmethodology allows for a more productive analysis when presented with ultra-trace amounts of sample.

© 2010 Forensic Science Society. Published by Elsevier Ireland Ltd. All rights reserved.

1. Introduction

The extraction of ultra-trace analytes using nanomanipulation-coupled to nanospray ionization-mass spectrometry (NSI-MS) hasproven to be a very effective tool. Extraction of trace drug particulatesfrom fibers has been documented using this method [1] as well asthe extraction of peptides from individual beads [2]. Both of thesetechniques employed nanomanipulation-coupled to NSI-MS andshowed high reproducibility when compared with traditional meth-ods of analysis yielding quality results. Thismethodof analysis exhibitsextreme sensitivity with limits of detection in the picomole range [1].This demonstration of sensitivity holds the potential for ultra-traceextraction of analytes from a myriad of matrices.

The very nature of matrix effects has been an issue for trace druganalysis. It remains a prominent issue in biological samples toward thelimits of detection/quantitation in biological fluid based matrices [3].Many factors, such as the instrumentalmethods involved, the ionizationmethod employed, or sample preparation procedures, can influence theoverall effectiveness of the analysis. Trace analysis of contaminants fromfood products carries the same burden even after an extensive cleanupprocedure of the samples has beenperformed [4]. These factors limit theoverall quality of analysis, producing results that are not reliable. Ingeneral, accurate quantitation of ultra-trace analytes is difficult to obtaindue to these limitations.

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Ultra-trace techniques differ according to the type of analysisbeing executed. Many techniques utilised for ultra-trace analysis havebeen developed to overcome the issue of matrix effects. However, theactual quantitation of ultra-trace amounts varies depending on thetype of sample being analysed. There is no clear cut definition of theword and so most scientists refer to the quantity being under 1 ppm[5]. Innovative techniques developed for ultra-trace work in druganalysis include instrumental methods such as affinity probe capillaryelectrophoresis [6] and supercritical fluid extraction [7]. Throughaffinity probe capillary electrophoresis, drug quantitation can beachieved in the picomolar range from biological matrices [6].Supercritical fluid extraction has been combined with solid phaseextraction to detect ultra-trace amounts of drug metabolites fromplasma [7]. Various methods utilizing mass spectrometry includetechniques where solid phase extraction is coupled to liquidchromatography coupled to electrospray-tandem mass spectrometryfor the detection of illicit drugs and their metabolites from sewagewater [8]. This method provides an automated system of analysiswhere high throughput is achievable while maintaining sensitivity inthe nanogram range. Liquid chromatography-electrospray ionizationtechniques are utilised more for the analysis of drugs due to thesuperb structuring detail of molecules that can be obtained fromspectra when drugs are analysed in various matrices [9]. Liquidchromatography coupled to quadrupole-time-of-flight mass spec-trometry for the detection of illicit drugs in oral fluids presentsanother type of liquid chromatography-mass spectrometry methodutilised for drug detection [10]. Thesemethods are an improvement ofolder conventional methods in regards to precision, accuracy, andselectivity. However, the actual application of these techniques is still

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Fig. 1. Image captured of a footwear impression made at a crime scene.

197N. Wallace et al. / Science and Justice 51 (2011) 196–203

a tedious detailed analytical process requiring a good deal of time forsample cleanup and preparation along with a suitable amount of timeto complete analysis.

Other improvements made in ultra-trace drug analysis that willemphasise immediacy with accuracy include such techniques asoptical chemical imaging [11]. Solid surface luminescence of minutedrug amounts frommatrices can be achieved.With this technique, theneed for sample preparation is eliminated while maintainingdetection limits in the picogram range. Raman spectroscopy hasbeen used to detect quantities of street cocaine from the surface ofhuman tissue matrices [12]. This method is very efficient for detectionof trace analytes. An improvement of this method is Surface EnhancedRaman scattering (SERS) where narcotics on a metal surface can bedetected in the attogram range [13]. The only drawback of thismethod is that it requires a very controlled environment in order tomaintain the chemical and electronic effects of analysis due to thespecialty of the SERS method which focuses on the substrate beingutilised along with the manner of analyte adsorption. There is nouniform method for performing SERS; it varies according to theanalyte. The coupling of Raman Spectroscopy with IR has proven to bebeneficial for immediate quantitation of cocaine amongmixtures [14].Discrimination of the concentration of various components in a solidmixture can be determined with this method. The only limitationregarding this method is the large amount of sample needed to obtaina reasonable amount of accuracy. Surface probing techniques such asdesorption electrospray ionization (DESI) provide a rapid and directapproach to ultra-trace analysis eliminating the need for samplepreparation [15]. DESI releases charged droplets onto the surface forionization of analytes. Direct analysis in real time (DART) is anotherhigh throughput surface method similar to DESI that releases excitedstate gas molecules for ionization of the analytes on the surface [16].Although high sensitivity is attainable with DESI and DART, it requiresa suitably large amount of surface area for analyte ionization. Furtherimprovements with these methods could be possible with theimplementation of imaging techniques.

The imaging capabilities that accompany mass spectrometricanalysis serve as a great tool toward various types of analyses. Theseimaging capabilities can provide valuable information on spatial andchemical facets of analysis [17]. Most imaging mass spectrometrymethods are employed in biological applications for the chemicalimaging of analytes in tissues and protein extraction. Imaging massspectrometry has made significant headway in the study of proteomics[18]. The various imaging techniques employed have enhanced thestudy of cell and gene function at the protein level. Imaging techniquesnot only can facilitate the probing of analytes, but also can provide ameans of verifying the geometric and luminescent properties ofparticular analytes among a matrix using fluorescence microscopy[19]. This can be used as a way of determining the identity of theanalytes being studied. Fluorescencemicroscopy techniques are utilisedvery often in protein studies. These techniques serve as a great tool forthe spectral imaging of fluorescing proteins in molecular samples,where imaging of the structural network of proteins within a moleculecan be obtained by coupling fluorescence microscopy with FourierTransform spectroscopy. [20] Fluorescence microscopy is commonlyapplied toward the analysis of solid phase analytes to determine andverify the characteristic luminescent properties unique to the analyte[19].

The application of the electrostatic dust lifter towards the retrievalof particulates on various surfaces has been utilised mostly towardsthe lifting of prints at crime scenes. Fig. 1 displays an image taken of afootwear impression made at a crime scene. Documentation of dustprints at crime scenes is essential to police investigations for itprovides evidence of footwear impressions made by the suspect [21].This method of retrieval has shown tremendous results towardidentifying print patterns from footwear showing high sensitivity forfootwear identification. [22] The same method of particle retrieval is

applied toward lifting drug residues. The electrostatic lifting processutilises a static electricity instrument that provides a voltage to ametallic film for the lifting of dust particles [23]. This process isapplied to drug residues where the metalised plastic film is placedover the residue sample and is lifted by applying voltage to the filmwith a high voltage probe. Normally, crime scene photographs aretaken of footwear impressions after a lift has been done since the dustparticles are not permanently affixed to the film. They only adhere tothe film for a limited amount of time. The image of the impression isusually the sole purpose of doing the electrostatic lifting process asthey are kept for evidence. However, in the method being introducedhere, the film lifts are packaged in airtight plastic bags following thecompletion of an electrostatic lift. The packaging allows for transfer tothe nanomanipulator for extraction. The ability to electrostatically liftultra-trace amounts of drug residues from crime scenes offers a morepractical approach toward the collection of drugs for analysis.

The application of nanomanipulation-nanospray ionization to theextraction of ultra-trace drug residues retrieved by the electrostaticlifting process can provide a more efficient means of performinganalysis on drug quantities in the picogram to attogram range. Thesamples are adequate in size and quantity for this type of analysis,providing ample signal for detection. Particle extraction from amatrixis achieved allowing deconvoluted spectra to be produced as todetermine the identity of the analyte. This innovative and simplisticmethod of drug analysis allows for high quality analysis of ultra-traceresidues of illicit drugs while eliminating the tedious, multi-stepsample preparation process.

2. Materials

The illicit drugs electrostatically lifted and ultimately analysed inthis method included rock cocaine (0.0043 g total), crystal metham-phetamine (0.0033 g total) and black tar heroin (0.0034 g total). Alldrugs were provided by the University of North Texas PoliceDepartment (Denton, TX). The method was validated using~0.0025 g of caffeine (Alfa Aesar, Ward Hill, MA) per lift. Powdercocaine (0.0030 g total) was used in the preliminary studies. Eachsample was mixed with a sand based soil (0.0021 g per sample). Eachsample was also mixed separately with potting soil (0.0021 g persample) formatrix studies. Prior to electrostatic lifting, half themass ofeach analyte was reserved for Raman spectroscopy and UV fluores-cence. The solvent mixture used for dissolution and extraction of

198 N. Wallace et al. / Science and Justice 51 (2011) 196–203

samples was a 1:1(v/v) solution of optima LC/MS methanol (FisherScientific, Fair Lawn, NJ) andMillipore water (Millipore, Billerica, MA)with 1% glacial acetic acid (Malinkrodt Chemical Co., Phillipsburg, NJ).The methanol used was doubly distilled to eliminate any impurities inthe solvent. The electrostatic lifting of each sample was done with anElectrostatic Dust Print Lifter (Kinderprint (Model No. 3C), Martinez,CA) utilizing metalised plastic films for each lift. The nanomanipulator(Zyvex, Richardson, TX) -coupled to a MultiZoom AZ100 microscope(Nikon, Melville, NY) along with a PE2000b four-channel pressureinjector (MicroData Instrument Inc., S. Plainfield, NJ) was used forextraction of the analytes from the film lifts. The mass spectrometricanalysis was done on a LCQ DECA XP Plus (Thermo Finnigan, San Jose,CA) with a nanospray ionization source (Proxeon Biosystems, Odense,Denmark). Raman spectroscopy lift studies were carried out on aT64000 (Jobin Yvon, Cedex, France) coupled with a Coherent Innova90 argon ion laser (Laser Innovations, Santa Paula, CA) with a 488 nmline. Prior to completing Raman spectroscopy, the films were coatedwith a 50 nm layer of gold (93.999% purity) to enhance the Ramansignal. The film lifts also underwent UV fluorescence studies with aNikon Eclipse E600 (Nikon, Melville, NY) microscope attached to anEXFO X-cite 120 fluorescence illumination system (EXFO, Canada). ATE2000U Inverted Microscope was utilised for the UV fluorescencestudies of crystal methamphetamine.

3. Methods

3.1. Electrostatic lifting

The Kinderprint Electrostatic Dust Print Lifter is utilised in thismethod for the electrostatic lifting of the drug residues from a smoothtable surface. The electrostatic lifter is a high voltage power unit(120 v/60 Hz)with an adjustable voltage. This power unit was utilisedalong with a high voltage probe used for lifting and a ground lead,which connects to a ground source. Each drug/soil sample and thecaffeine/soil sample were electrostatically lifted at a medium voltagerange for 30 s off of the surface of a table. The ground lead wasconnected to the metal leg of the table for a ground source. Each liftwas done with a 1.5 cm×1.5 cm section of metalised plastic film. Themetalised side of the plastic film is where the charge takes place withthe high voltage probe during lifting. After each electrostatic lift wascompleted, the films were folded over and packaged separately inairtight plastic bags for transfer to the nanomanipulator.

3.2. Nanomanipulation

Each lift collected was placed under the MultiZoom AZ100microscope for viewing and probing of drug and caffeine residuesfrom each of the mixtures. A metal fixture was used to secure eachfilm lift. Viewing and probing of each sample took place with an AZPlan Fluor 2× objective. Image capturing was done on NIS Elementssoftware, which was coupled to the microscope with a CCD camera.

The nanomanipulator mounted to the microscope consists of fournanopositioners controlled in either coarse or fine mode. The range ofmotion and the resolution achievable is dependent on the mode ofmanipulation. The coarse mode has a range of motion of 12 mm in theX and Z-axes and 28 mm in the Y-axis with a translational resolutionof 100 nm. In the fine mode of operation, the range of motion is100 μm in the X and Z-axes and 10 μm in the Y-axis. The coarse modeutilises nanospray capillary tips coated with Pt that perform theinjection and extraction of the analytes. All of the electrostatic liftswere manipulated with the coarse mode of operation. The PE2000bpressure injector provides the pressure required to do the injection/aspiration process through the nanospray capillary tips.

Analyte injection/extraction process was carried out with 10 μLof solvent loaded into the nanospray capillary tips. After theanalytes were located among the soil particles, the nanospray

capillary tip was landed on the desired particle of interest at ~1 μmaway. An injection of the solvent mixture (1:1 (v/v) methanol/water, 1% acetic acid) was performed at a pressure of 25 psi fordissolving process of the analyte. After 10 s of dissolution, thesolvent/analyte solution was aspirated into the nanospray capillarytip at a pressure of 40 psi. The nanospray capillary tip was thentransferred to the nanospray ionization source (NSI-MS). Anionization voltage of 2.5 kV was applied for analysis on the massspectrometer. After NSI-MS analysis took place, a wash of theremaining analyte/soil mixture was carried out with 200 μL ofsolvent mixture (1:1 (v/v) methanol/water, 1% acetic acid) andthen centrifuged down for 30 s to separate the soil particles fromthe drug solution. Analysis with electrospray ionization massspectrometry (ESI-MS) was conducted afterwards. An ionizationvoltage of 4.0 kV was applied along with a syringe pump flow of10 μL/min. This procedure was repeated for each drug/soil mixturelift.

3.3. Raman spectroscopic analysis

Metalised plastic films (1.5 cm×1.5 cm) coatedwith 50 nm of gold(93.999% purity) were utilised in the lifting of each drug analytewithout the soil matrix in order to do qualitative studies of eachparticular lift for Raman spectroscopy. The T64000 Groupe Horibawith a factory built stereomicroscope attached was utilised to gainspectra of each analyte lifted. Each lift was held in place bymetal stageholders while being viewed under a 100× objective. They wereimaged with a CCD camera along with the appropriate software. Thespectroscopic analysis of each lift was done with an argon ion laser at488 nm. The procedure was repeated for each analyte/soil mixture.

3.4. UV fluorescence analysis

The drug/soil (sand based) mixture lift was viewed with the E600microscope coupled to a fluorescence illumination system. Anobjective of 4× was used to observe the illumination of the drugparticles among the soil matrix on the films. Images were capturedwith a CCD camera along with appropriate software. Crystalmethamphetamine particles with potting soil were viewed underthe TE2000U Inverted Microscope coupled to a fluorescence illumi-nation system using an objective of 10×/0.30.

4. Results and discussion

In preliminary studies using caffeine, a caffeine/sand-based soilmixture was electrostatically lifted and underwent nanomanipulation-coupled with NSI-MS. The caffeine/sand-based soil mixture wascompletely lifted onto themetalised plastic film during the electrostaticlifting process. The caffeine particles on the lift can be seen among thesoil particles viewed through the microscope (Fig. 2a). A spectrumwasobtained from the injection/extraction process of the caffeine particlesfrom the lift utilizing NSI-MS. The amount of solvent used for injection/extraction was less than 10 μL utilizing a total analysis run time of lessthan two minutes. The MH+ peak for caffeine appears at m/z 195.13.Fig. 3 shows this peak at a leading intensity. Preliminary studies alsoincluded a powder cocaine/sand based mixture as well following thesame procedure as the caffeine sample. Fig. 4 shows the NSI-MS and theESI-MS spectrum of the powder cocaine/sand-based soil mixture.

The caffeine extraction from the soil matrix shows that singlecrystal extraction provides ample signal for detection of analytesthrough nanomanipulation-coupled to NSI-MS. The metalised plasticfilm lift provides a great platform for the extraction of particles as wellas an illuminating colorful background under the light source of themicroscope. The caffeine/sand-based soil particles appear enhanceddue to this illuminating background thus facilitating the probing ofthe analytes among the soil matrix. The powder cocaine extraction

Fig. 2. (a–e) Lifts containing the drug/sand-based soil mixtures. The nanospray tip is landed within micrometers of the analyte particles ready for the injection/extraction.(a) Caffeine/soil particles. (b) Powder cocaine/soil particles. (c) Rock cocaine/soil particles. (d) Crystal methamphetamine/soil particles. (e) Black tar heroin/soil particles.

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from the soil matrix also shows exceedingly well results confirminghow well the single crystal extraction process facilitates analysis. TheESI-MS wash of the powder cocaine lift demonstrates how ESI-MSalone does not show high selectivity toward the extraction of powdercocaine crystals as does nanomanipulation-coupled to NSI-MS.

All three drug/sand-based soil mixtures underwent the sameprocess as the caffeine and powder cocaine extractions. The sample

Fig. 3. The mass spectrum of the caffeine/sand-based soil particle extraction taken inthe positive mode with NSI-MS. The MH+ peak for caffeine is the most prominent peakat m/z 195.13.

amount reserved for each drug lift completely adhered to the filmthrough the electrostatic lifting process for the sand based soilmixtures; no particles were left behind on the table surface. Thepotting soil mixtures underwent the same process described above.However, the potting soil particles were not lifted in their entirety foreach lift. In addition to nanomanipulation-coupled to NSI-MS, a washwas performed on the remaining analyte/soil mixtures from each lift

Fig. 4. The NSI-MS spectrum of powder cocaine at a leading intensity ofm/z 304.13. Theinset shows the ESI-MS spectrum of powder cocaine/sand-based soil wash from the lift.TheMH+ peak for cocaine is seen within the grass region of the spectrum atm/z 304.73.

Fig. 6. The NSI-MS spectrum of the crystal methamphetamine particle extraction fromthe lift. A prominent signal appears at m/z 150.27 for the MH+ peak of crystalmethamphetamine. The inset shows the ESI-MS spectrum of the crystal methamphet-amine/sand-based soil wash from the lift. A prominent signal appears atm/z 150.27 forthe MH+ peak of crystal methamphetamine.

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and underwent electrospray ionization-mass spectrometry for com-parison of both methods of ionization. Nanomanipulation coupled toNSI-MS analysis was not done on the drugs mixed with the pottingsoil due to the size of the soil particles. Particles could not beextracted with the nanospray capillary tips. However, ESI-MS studieswere done on the washes. Fig. 2a–e displays the images captured ofthe lifts. The spectra taken from ESI-MS and NSI-MS mixed with thesand based soil are shown in Figs. 5–7. Fig. 8a-c shows the ESI-MSspectra of the drugs/potting soil mixtures. Studies with the caffeineand rock cocaine were extended to performing MS–MS analysis toobserve the breakdown products of these analytes as to eliminatefalse positives that could occur from background matrices. Fig. 9displays the MH+ peaks for each analyte along with their collisioninduced dissociation (CID) products, making the identification near-absolute.

A study of the MH+ peaks were done for each drug lift to observethe sensitivity and detection limits of each ionization method in theextraction of the analytes from each lift. Fig. 5 shows the MH+ peakfor rock cocaine in both NSI-MS and ESI-MS spectra leading at m/z304.33. When observing the intensity for the rock cocaine spectra, theintensity appears to be higher for the NSI-MS spectrumby 6 times thatof ESI-MS. For the leading MH+ peak at m/z 150.2 in the crystalmethamphetamine spectra, the NSI-MS spectrum shows intensity 1.5times higher than the ESI-MS spectrum (Fig. 6). In Fig. 7, the leadingMH+ peak at m/z 370.33 for black tar heroin has intensity 6 timeshigher in the NSI-MS spectrum than the ESI-MS spectrum. This is thesame magnitude for the rock cocaine spectra. Overall intensity forNSI-MS analysis appear higher for the drug extractions showing thatsensitivity of these analytes are greatly enhanced with the nanosprayionizationmethod. The study is continuedwith theMH+ peak areas ofeach drug to understand how detection limits are affected with bothmodes of ionization. The ion count ratios were calculated for eachdrug lift to determine how well the particles were detected. Table 1shows these ratio calculations of the each drug lift with sand-basedsoil and potting soil in NSI and ESI mode.

Area calculations were taken for each MH+ peak in order to get apeak to background ratio. Table 2 displays the area calculations for theMH+ peaks along with the background area for each drug. Accordingto the table, black tar heroin shows a peak to background ratio of19.8% for ESI-MSwhile its NSI-MS spectrum shows a ratio of 40.8%. Forthe rock cocaine, the peak to background ratio from ESI-MS is 44.1%while NSI-MS shows a ratio of 65.5%. Crystal methamphetamine has apeak to background ratio of 48.2% while NSI-MS shows a ratio of69.2%. An average area increase of 21% is observed for the NSI-MSanalysis of each drug. This study shows that detection limits areactually lower with NSI-MS.

Fig. 5. The NSI-MS spectrum of the rock cocaine particle extraction from the lift. Aprominent signal appears at m/z 304.33 for the MH+ peak of rock cocaine. The insetshows the ESI-MS spectrum of the rock cocaine/sand-based soil wash from the lift. Aprominent signal appears at m/z 304.33 for the MH+ peak of rock cocaine.

The ESI-MS spectra of the drugs with potting soil in Fig. 8 displaythe MH+ peaks for each drug along with peaks from the potting soilparticles. These spectra indicate how efficiently electrostatic liftingretrieves particles from the table surface. The particle sizes of thepotting soil did not allow passage through the nanospray capillarytips. The drugs dissolved quickly into the potting soil and thereforecould not be extracted. However, sensitivity of the ESI-MS analysis isseen from looking at the spectra. Rock cocaine and crystal meth MH+

peaks show higher intensities than the black tar heroin, as seen inFig. 8 a–c. The black tar heroin MH+ peak may have interference fromthe potting soil particles. Adequate intensity is shown for this peakeven with the interferences.

The electrostatic lift studies were done with Raman spectroscopyto investigate the adherence of the analytes to the metalised plasticfilm. In order to obtain the Raman spectra for the drug lifts, themetalised plastic films were plated with 50 nm of gold (93.999%purity) on the non-metalised side of the film. As before, the lifts werecompleted on a table surface. In the electrostatic lifting process forrock cocaine, a medium voltage range was applied in the liftingprocess for ~30 s. Two of the particles were left behind while theothers lifted onto the film. Fig. 10a and c shows the image capturedalong with the Raman spectrum obtained from the lift. The procedurewas repeated for crystal methamphetamine and black tar heroin. Inthe electrostatic lifting process for crystal methamphetamine, twoattempts were required in order for the majority of the particles to

Fig. 7. The NSI-MS spectrum of the black tar heroin extraction from the lift. A prominentsignal appears at m/z 370.33 for the MH+ peak of black tar heroin. The inset shows theESI-MS spectrum of the black tar heroin/sand-based soil wash from the lift. Aprominent signal appears at m/z 370.33 for the MH+ peak of black tar heroin.

Fig. 8. (a) The ESI-MS spectrum for the black tar heroin/potting soil wash from the lift.The MH+ peak for black tar heroin appears at m/z 370.33 along with peaks fromthe potting soil. (b) The ESI-MS spectrum for the rock cocaine/potting soil wash fromthe lift. The MH+ peak for rock cocaine appears at a leading intensity at m/z 304.27.(c) The ESI-MS spectrum for the crystal methamphetamine/potting soil wash fromthe lift. The MH+ peak for crystal methamphetamine appears at leading intensity atm/z 150.27 along with peaks from the potting soil.

Fig. 9. (a) The MS–MS spectrum of caffeine. The MH+ peak ofm/z 195.00 appears alongwith the degradation products. (b) The MS–MS spectrum of rock cocaine. The MH+

peak ofm/z 303.80 appears along with the degradation products. The inset displays theexpanded view of the degradation products occurring at a lower intensity.

Table 1Ratios of ion count calculated for each drug lift. The table shows the ratios for drug liftsdone with both potting soil and sand based soil with NSI-MS and ESI-MS.

NL TIC Ratio

Drug/(sand-based soil) (NSI-MS)Black tar heroin 8.06E+07 2.51E+09 3.21E−02Rock cocaine 2.34E+09 4.02E+09 5.82E−01Crystal methamphetamine 4.92E+07 6.71E+08 7.33E−02

Drug/(sand-based soil) (FSI-1S)Black tar heroin 1.55E+07 7.74E+08 2.00E−02Rock cocaine 1.06E+08 1.91E+09 5.55E−02Crystal methamphetamine 4.95E+07 7.95E+08 6.23E−02

Drug/(potting soil)(ESI-MS)Black tar heroin 3.07E+08 1.06E+10 2.90E−02Rock cocaine 2.76E+08 4.40E+09 6.27E−02Crystal methamphetamine 6.41E+07 2.03E+09 3.16E−02

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adhere to the lift. Two to three particles were left behind on the tablesurface from the original amount. Fig. 10b and d shows the capturedimage of the crystal methamphetamine on the gold plated film alongwith the Raman spectrum obtained.

The electrostatic lifting process for the black tar heroin requiredfour attempts to lift the drug particles. Only one particle from theoriginal amount adhered to the film. No results could be obtained forthe Raman spectroscopic analysis of the black tar heroin. No detectionof analyte could be seen nor could an image be captured in goodquality. The rock cocaine and crystal methamphetamine particleswere favorable toward Raman spectroscopic analysis as can be seenfrom their spectra. The gold plated films, in some instances, required

more attempts to lift the analytes and did not retrieve all of theparticles present, Fig. 10c and d displays obvious detection of analytepresent from the lifts. Raman spectroscopic studies were extended toanalyse rock cocaine in a blind soil mixture in order to verify detectionof the analyte from the matrix. Fig. 11 displays the image of rockcocaine crystal along with its spectrum. Raman imaging can beperformed on peaks of interest, utilizing the nanomanipulator-coupled to MS for near-absolute identification with CID.

UV fluorescence studies were done in addition to Ramanspectroscopy studies in order to differentiate the drug particles fromthe soil matrix on the lifts. Fig. 12a shows the RGB fluorescence of the

Table 2Peak area calculations of black tar heroin, crystal meth, rock cocaine taken from themass spectra. Peak area ratios are shown for both NSI-MS and ESI-MS analysis of eachdrug.

Drugs m/zBackgroundrange

m/z MH+peakrange

MH+peakarea

Bkg. area Bkg. arearatio

Black tar heroin(ESI-MS)

300.07to 400.0

369.53to 370.87

7.45E+06 3.77E+07 l.98E−0l

Black tar heroin(NSI-MS)

300.07to 400.0

369.53to 370.88

3.86E+07 9.47E+07 4.08E−0l

Rock cocaine(ESI-MS)

200.07to 500.0

303.47to 304.80

1.64E+07 3.71E+07 4.41E−01

Rock cocaine(NSI-MS)

200.07to 500.1

303.47to 304.87

1.15E+08 1.76E+08 6.55E−01

Crystal meth(ESI-MS)

100.07to 300.0

149.47to 150.73

1.42E+07 2.94E+07 4.82E−01

Crystal meth(NSI-MS)

100.07to 300.1

149.33to 150.8

2.21E+07 3.20E+07 6.92E−0lFig. 11. The rock cocaine Raman spectrum obtained from the gold plated lift. The insetdisplays the image of the rock cocaine crystal located among the soil mixture.

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rock cocaine/sand-based soil mixture. The RGB fluorescence exhibitsthe rock cocaine particles among the soil mixture. The imaging ofthe rock cocaine particles is clearly seen from the soil matrix withthe RGB fluorescence. The RGB fluorescence image of the crystalmethamphetamine particle is clearly seen among the potting soilmixture shown in Fig. 12b. This analysis was done using the invertedmicroscope for crystal methamphetamine since fluorescence couldnot be seen with the crystal methamphetamine on the film lift mostlikely due to the black background of the film. No images were takenof the black tar heroin particles. Fluorescence could not be seen withthe black tar heroin among the soil particles.

5. Conclusion

The introduction of electrostatic lifting with nanomanipulation-coupled to nanospray ionization mass spectrometry demonstrateseffectively how ultra-trace amounts of drug particles can be lifted andextracted with ease, eliminating the need for a preconcentrationtechnique. The quantity of particles lifted through the electrostatic

Fig. 10. (a) Image captured of rock cocaine particles on the gold plated lift with laser appliedlaser applied. (c) The rock cocaine Raman spectrum obtained from the gold plated lift. (d)

lifting process is sufficient for NSI-MS analysis. The nanomanipulator-coupled to the microscope provides an efficient means of extractionby bringing the nanospray tip to the sample. As can be seen from thedrug spectra, single crystal extraction provides ample signal fordetection for these analytes. Higher selectivity is achievable with thismethod as opposed to ESI-MS alone. Nanomanipulation-coupled toNSI-MS provides the benefit of being able to select the analyte(s) ofinterest among a matrix. The imaging software utilised provides anenhanced capability to locate the analytes among the matrix in orderto complete extraction. Raman spectroscopic studies revealed thedetection of analytes that were electrostatically lifted. Although thesestudies did not reveal any information for the black tar heroin, it canbe understood that the crystalline forms of these analytes are mostpreferable for lift and detection with microscopy. The Ramanspectroscopic studies still indicate that the electrostatic lifting processis effective in lifting ultra-trace particles, even the black tar heroin.The data from the NSI-MS spectra on the drug lifts verify the parention peaks of the drugs. The MS–MS spectra provide qualitativeverification of the drug analytes according to their degradation

. (b) Image captured of a crystal methamphetamine particle on the gold plated lift withThe crystal methamphetamine spectrum obtained from the gold plated lift.

Fig. 12. (a) The RGB fluorescence image captured of the rock cocaine/sand-based soilmixture. (b) The RGB fluorescence image captured of the crystal methamphetamine/potting soil mixture.

203N. Wallace et al. / Science and Justice 51 (2011) 196–203

products. Both the NSI-MS and MS–MS spectra demonstrate theenhanced sensitivity and selectivity of utilizing mass spectrometry,providing non-contestable results as to the identity of the analytes.The UV fluorescence imaging studies exhibited the drug particlesamong the soil matrix. The utilization of this imaging technique can beapplied in the extraction of analytes in mixtures where the matrixappears to dominate under normal microscopic view. In addition tothis imaging technique, the capabilities to distinguish the uniquegeometric shapes of drug crystals could be applied as well to thenanomanipulation method.

The utilization of nanomanipulation-coupled to NSI-MS hasalready proven to be advantageous in the analysis of trace particlesfrom previous experimental studies. The lifting of drug particles fromthe electrostatic process provides an innovative means to collect drugresidues in ultra-trace amounts. This process combined withnanomanipulation-coupled to NSI-MS displays a new technique ofcollection and extraction where the quantity of the particles is not alimitation for analysis. The usage of this combinedmethod could be animprovement in many types of trace analysis.

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