Microchemical Journal 115 (2014) 106–112

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Microchemical Journal

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Analysis of gunshot residues produced by .38 caliber handguns usinginductively coupled plasma-optical emission spectroscopy (ICP OES)

Gabriela Vanini a,⁎, Rafael M. Souza a, Caline A. Destefani a,b, Bianca B. Merlo b, Tânia M. Piorotti b,Eustáquio V.R. de Castro a, Maria Tereza W.D. Carneiro a, Wanderson Romão a,c,⁎a Laboratório de Petroleômica e Forense, Departamento de Química, Universidade Federal do Espírito Santo, 29075-910 Vitória, ES, Brazilb Laboratório de Química Legal, Superintendência de Polícia Técnico-Científica do Estado do Espírito Santo, 29045-402 Vitória, ES, Brazilc Instituto Federal do Espírito Santo, 29106-010 Campus Vila Velha, ES, Brazil

⁎ Corresponding author at:Núcleo de CompetênciasFernando Ferrari, 514, Goiabeiras, Vitória, ES, 29075-910,

E-mail addresses: gabrielavanini@hotmail.com (G. Vanwandersonromao@gmail.com (W. Romão).

http://dx.doi.org/10.1016/j.microc.2014.03.0030026-265X/© 2014 Elsevier B.V. All rights reserved.

a b s t r a c t

a r t i c l e i n f o

Article history:Received 2 December 2013Received in revised form 3 March 2014Accepted 3 March 2014Available online 11 March 2014

Keywords:Ballistic forensicsFirearms leadBariumAntimonyICP OES

A new analytical method is proposed for the collection and quantification of gunshot residues (GSRs) from fire-arms using inductively coupled plasma optical emission spectrometry (ICP OES). Lead (Pb), barium (Ba) andantimony (Sb) concentrations in GSR from .38 caliber Taurus® handguns were monitored, and three importantmethodologies were evaluated such as: i) the collection region of the hand of the shooter; ii) tape-type versusswab collectors; and iii) GSR quantification from the right and left hands. Pb, Ba and Sb were found in four ofthe hand regions analyzed (palm, back, thumb and forefinger palm (TF-palm), and thumb and forefinger back(TF-back)), with their concentrations increasing as a function of the number of shots (one, three and five).Leadwas found to be themost abundant species present. In terms of relative analytical sensitivity, higher concen-trations of these three elements are mainly found in the back, TF-palm and TF-back regions. The effect of handwashing was also evaluated, which the TF-palm and the TF-back regionsmaintained sensitivity for the detectionof three elements (concentrations higher than 4.56 μg L−1) for only three and five shots. Among the collectiondevices analyzed, swab collectors (dry, moistened with EDTA, andmoistened with water) presented higher sen-sitivity than tape-type collectors (adhesive, double-sided and adhesive-plaster). Additionally, swabs are a moreeconomical collection device, providing a simple and fast collection method that does not require microwavedigestion. Pb, Ba and Sb concentrations were also evaluated on the left and right hands. It was observed thatPb is mainly found on the right hand, whereas Ba and Sb concentrations are similar on both hands. ICP OES istherefore a powerful tool for GSR analysis, providing multielemental quantification of Pb, Ba and Sb.

© 2014 Elsevier B.V. All rights reserved.

1. Introduction

Violence directly affects civil society. Firearms are used in 71% of allhomicides in Brazil, corresponding to approximately 35,000 homicidesper year. Therefore, the development of new analytical methodologiesin ballistic forensics is important. Ballistics represents a sub-area ofcriminalistics that includes the study of firearms and ammunition, inwhich the main goal is to relate the suspect to the murder weapon,most often through the ammunition [1]. Firearm ammunition consistsof the projectile, case, propellant and primer mixture, the last ofwhich contains lead styphnate (C6HN3O8Pb), barium nitrate, antimonytrioxide, antimony tetroxide and aluminum. Generally, the primer

em Química do Petróleo, Av.Brazil. Tel.: + 55 27 3145 4502.ini),

mixture is compressed by the firing pin, where the C6HN3O8Pb andantimony tetroxide crystals are broken, initiating combustion [1,2]. Asa consequence of combustion, residues are formed that contain oxidesof carbon (CO and CO2), water and metal oxides (lead oxide, bariumoxide and antimony oxide) [1]. During firing, a considerable amountof material in the gaseous or solid aerosol phase is produced and ex-pelled along with the projectile. Part of the gaseous material solidifies,producing gunshot residues (GSR). GSR is composed of the elementslead, barium and antimony [3], which can be found primarily depositedon the shooter's hands, face and clothes; on people close to the firearmdischarge; and even on the victim [4].

In Brazil, the colorimetric test utilizing the reagent sodiumrhodizonate (Feigl–Suter reaction) has been routinely used; however,this test only detects Pb [5]. Despite its lower cost, one of the majorproblems with this test is contamination with other materials, whichleads to false positive results [6].

Recently, several studies have reported new analytical techniquesfor identifying firearms fromGSR [3,4,7–11]. Among them, the scanning

Table 2Main microwave operating conditions.

Collectors (tape) Parameters Stage 1 Stage 2 Stage 3

Adhesive and Scotch® Temperature (°C) 200 200 CoolingRF Power (W) 700 1000Time (min) 12 6

Double-sided andadhesive-plaster

Temperature (°C) 220 250 CoolingRF power (W) 700 1000Time (min) 12 20

107G. Vanini et al. / Microchemical Journal 115 (2014) 106–112

electron microscopy/energy X-ray spectroscopy technique, SEM/EXS[12–15], has been used and supported by a large number of experts be-cause it allows for the correlation of themorphology and chemical com-position of individual particles composed of Pb, Ba and Sb [16–18].However, in July 1998, the Brazilian Cartridge Company (CBC) startedthe production and marketing of clean range ammunition [1]. This am-munition contains a primer composed of the non-heavy metals Ti, Cuand Zn, and the projectiles are completely covered, thereby preventingany contamination with Pb. The use of the clean range ammunition hasmade the SEM/EXS technique ineffective, as no spherical particles con-taining Pb/Ba/Sb are produced by this ammunition when fired [19].Furthermore, SEM/EXS requires a considerable amount of analyst timeand expensivemaintenance, and therefore, its implementation as a rou-tine technique in forensic laboratories has come into question. Otherimportant analytical tools have been highlighted in forensic ballistics,such as X-ray fluorescence (XRF), inductively coupled plasma massspectrometry (ICP-MS) and inductively coupled plasma optical emis-sion spectrometry (ICP OES). Berendes and collaborators [20] reportedthe first use of XRF to produce micro-images of the Pb, Ba and Sbelements in GSR produced from conventional ammunition and fromclean range ammunition (Ti, Cu and Zn). Despite the XRF techniquebeing multi-elementary, selective, non-destructive, rapid and inexpen-sive, its main disadvantage is its low sensitivity (generally µg g−1),which can lead to false negative results [2].

ICP-MS and ICPOES present higher sensitivity thanXRF (fromng g−1

to mg g−1); thus, these techniques appear to be more promising andversatile. Reis and collaborators [10] reported a new methodology forthe recovery and analysis of GSR containing Pb, Ba and Sb based on theuse of a swab moistened with a 2% (w/v) EDTA solution and ICP-MS[8,19]. Maxima and minima concentrations were found for Pb, Sb, andBa (7250 and 1.05; 108 and 0.72; and 482 and 1.25 μg L−1, respectively)after one shot from a .38 caliber handgun. Despite the high sensitivity ofthe ICP-MS technique, its high installation and maintenance costs havemade its implementation difficult. Herein, the ICP OES technique[21–26]was evaluated in the quantification of GSR using .38 caliber Tau-rus handguns containing Brazilian cartridges. Analytical methodologieswere applied to determine the most sensitive collection region fromthe hand of the shooter, choice of collector (tape-types: adhesive,double-sided, adhesive-plaster, and Scotch®; and swabs: dry,moistenedwith EDTA, andmoistened with water), and to evaluate the presence ofGSR on the right and left hands.

2. Experimental

2.1. Materials and reagents

The collection of GSR was performed in the Ballistic Laboratory ofthe Criminal Institute of Vitória City, Espírito Santo State, Brazil. The

Table 1Main ICP OES parameters.

RF power (W) 1350Coolant gas (L min−1) 15Auxiliary gas (L min−1) 0.2Nebulizer gas (L min−1) 1.2Sample uptake (mL min−1) 1.0Viewing AxialAnalyte wavelengths (nm) Pb = 220.353

Ba = 233.527Sb = 206.826

Limit of detection (μg L−1) Pb = 1.49Ba = 0.15Sb = 4.79

Limit of quantification (μg L−1) Pb = 4.97Ba = 0.50Sb = 15.97

firearm used was a Taurus® .38 caliber handgun and a CBC .38 SPLlead round-nose cartridge case.

Nitric acid (HNO3) of suprapure quality (65%, Merck Química Brasil,Brazil), ultrapure water (18.2 MΩ·cm), prepared by a reverse osmosissystem (PURELAB Mk2 Ultra, UK), hydrogen peroxide (Cromoline FineChemicals, Brazil), and ethylenediaminetetraacetic acid (EDTA, Sigma-Aldrich, USA) were used. The EDTA was used as a complexing agenton moistened swabs. All reagents and solvents were used as received.A stock multielemental solution containing 1000 μg L−1 of the stan-dards Ba, Sb and Pb (Sigma-Aldrich, Switzerland) was serially diluted(100, 200, 300 to 500 μg L−1) to form the calibration curve. All standardsolutions were acidified with 2% HNO3.

2.2. Instrumentation

An ICP OES (PerkinElmer, Model Optima 7000, USA) was used forthe quantification of Pb, Ba and Sb. A Meinhard concentric nebulizerand cyclonic spray chamber with peristaltic pumping were used for in-troducing the samples into the plasma torch. The operating parameterswere optimized using a central composite design. The optimized oper-ating parameters, as well as the values of the limit of detection (LOD)and limit of quantification (LOQ) of the analytes Pb, Ba and Sb, areshown in Table 1.

After the collection step, the samples were digested in an ultrasonicbath (Unique, Model UltraCleaner 1450, Brazil) and in a microwave(CEM, Model Xpress, USA). The program for microwave heating isdescribed in Table 2.

2.3. Evaluating the best collection region of GSR from the hand of the shooter

To evaluate the best collection region for GSR on the hands ofshooters, the four different regions were studied: palm, back, thumband forefinger palm (TF-palm) and thumb and forefinger back(TF-back), as shown in Fig. 1.

The GSR was obtained from six volunteers (three men and threewomen) who fired zero (or blank, 6)⁎, one (6),⁎ three (6) and fiveshots (6), in triplicate. The effect of handwashing on the ability to detectGSR on the shooters' hands was also evaluated (18)⁎. Thus, a total of 36samples were collected for each region analyzed. A swab moistenedwith a solution of 2% EDTA (w/v)was used as the collector [10]. Thefire-armswere cleaned before each test shot, thereby eliminating any possi-bility of prior contamination. The criterion adopted for the selection ofshooters consisted of people who did not have direct contact with sub-stances that could contain the three preponderant elements (Pb, Ba andSb), thus avoiding prior contamination [27].

The GSR samples were generally collected in the following order:i) before shooting (blank); ii) one shot; iii) hand washing; iv) threeshots; v) hand washing; vi) five shots; and vii) hand washing. For thehand washing step, a similar procedure was performed in all cases:the shooters hands were washed with coconut soap, vinegar and de-ionized water. The collectors containing GSR were stored in 15 mLpolypropylene tubes. After collection, to each tube, 2 mL of a 10%HNO3 (v/v) solution was added and diluted to a final volume of 10 mL.

⁎ Number in parenthesis represents the number of collected samples.

Palm BackThumb and

forefinger palm

Thumb and forefinger back

Fig. 1. Image of the collection regions of GSR from hands of shooters: palm, back, thumb and forefinger palm (TF-palm) and thumb and forefinger back (TF-back).

Fig. 2. Tape-type collectors: (a) adhesive, (b) double-sided, (c) adhesive-plaster and (d) Scotch®.

Fig. 3. Image of shooter holding a Taurus .38 caliber handgun.

108 G. Vanini et al. / Microchemical Journal 115 (2014) 106–112

The samples were then submitted to an ultrasonic bath for 20 min at25 kHz and heated in a water bath for 1 h at 100 °C. Finally, the swabswere removed by centrifugation, and the extracts were diluted to 10 mLwith deionized water and analyzed by ICP OES.

2.4. Evaluating the best collector

After choice of the collection region (TF-palm and TF-back), a studywas performed to determine the best collector. Six different methodsfor collecting GSR were studied: using swabs (dry, moistened withEDTA solution (2% w/v) and moistened with water) and using tape-type collectors (adhesive, double-sided, adhesive-plaster and Scotch®).The sequence of the shot,washing, and collection procedurewas similarto that described in previous sections (0, 1, 3 and 5 shots, in triplicate);however, only one unique volunteer was utilized. A total of 21 samples(sum of the blank (3) with the number of shots (9) and the number ofhand washing (9)) were collected for each collection device. The sameprocedure was also applied for the digestion step and for the extractionof GSR from the swabs (dry, moistened with EDTA solution (2% w/v),and moistened with water).

For the collection of GSR using tape-type collectors, two woodenspatulas were fixed at the ends of the tape, producing a collection areaof 3 cm2 (1.5 cm × 2 cm), as shown in Fig. 2. In all cases, only one sideof the tape-type collector was used. The extraction of GSR from thetape-type collectors was performed utilizing a microwave as previouslyreported [28]. Briefly, the wooden support was removed from the tape-type collector, and the remainder was inserted into a Teflon tube. Ineach tube, 5 mL of concentrated HNO3, 3 mL of a 30% (v/v) H2O2 solu-tion, and 2 mL of ultrapure water were added. The samples were then

submitted to extraction by microwave, and the main experimentalconditions are described in Table 2. Finally, the extracts were trans-ferred to polypropylene tubes, 5 mL of ultrapure water was added,and the samples were analyzed via ICP OES.

2.5. Pb, Ba and Sb quantification of GSR from the right and left hands of aright handed shooter

Herein, the ability of the ICP OES technique to detect GSR on the leftand right hands of a shooter (a unique volunteer) was evaluated. Thedry swab collection technique was applied to the TF-back and TF-palm

Table 3Pb, Ba and Sb concentrations (μg L−1) of GSR obtained from four different hand regions of male and female shooters: palm, back, thumb and forefinger palm (TF-palm) and thumb and forefinger back (TF-back). The values in parentheses are thestandard deviations from triplicate data.

Samples Palm Back TF-palm TF-back

Pb Ba Sb Pb Ba Sb Pb Ba Sb Pb Ba Sb

ManBlank 1.24 (0.01) bLOD 2.81 (1.80) 3.88 (0.01) bLOD bLOD bLOD bLOD bLOD 11.26 (0.01) bLOD bLOD1 shot 21.99 (0.01) 7.02 (0.08) 5.13 (1.81) 337.45 (0.01) 17.00 (0.21) 10.39 (1.60) 336.30 (0.01) 25.81 (0.03) 15.87 (0.65) 958.97 (0.01) 25.56 (0.39) 13.31 (0.23)3 shots 159.86 (0.01) 14.46 (0.20) 6.60 (1.13) 480.21 (0.15) 42.73 (0.01) 38.79 (1.13) 1369.87 (0.02) 63.80 (2.01) 25.32 (0.12) 1047.11 (3.11) 41.93 (0.79) 20.49 (1.02)5 shots 255.07 (0.01) 17.71 (0.44) 23.47 (2.91) 1138.50 (0.01) 124.83 (0.09) 139.18 (2.41) 1913.80 (0.02) 72.93 (0.07) 34.80 (0.93) 5183.18 (0.02) 92.12 (0.45) 33.41 (0.90)1 shot and washing bLOD bLOD bLOD 2.02 (0.01) bLOD 7.93 (1.4076) bLOD bLOD bLOD bLOD bLOD bLOD3 shots and washing bLOD bLOD bLOD 17.59 (0.01) 3.98 (0.01) bLOD 20.02 (0.01) 7.43 (0.07) 8.75 (0.03) 27.82 (1.45) 4.56 (2.01) 20.00 (3.01)5 shots and washing 1.90 (0.01) 6.10 (0.01) 8.98 (0.01) 222.47 (0.01) 4.08 (0.16) 27.31 (0.14) 220.48 (0.01) 29.35 (0.07) 27.69 (0.69) 626.95 (0.96) 14.61 (0.66) 28.89 (0.02)

WomanBlank bLOD bLOD bLOD bLOD bLOD bLOD bLOD bLOD bLOD 2.38 (0.01) bLOD bLOD1 shot 38.22 (0.01) 7.93 (0.07) bLOD 187.82 (0.01) 9.75 (0.09) 6.47 (1.70) 357.97 (0.01) 22.27 (0.36) 9.34 (0.89) 673.70 (0.01) 29.54 (0.27) 17.89 (0.82)3 shots 38.92 (0.01) 9.96 (0.55) bLOD 242.27 (0.01) 14.24 (1.14) 7.38 (0.01) 446.70 (0.99) 25.68 (1.01) 11.17 (2.55) 1045.78 (0.85) 35.72 (1.10) 23.82 (0.01)5 shots 289.50 (0.01) 23.42 (0.10) 26.42 (2.50) 1049.25 (0.01) 28.11 (0.09) 46.21 (0.40) 2145.78 (0.01) 45.93 (0.15) 27.21 (1.94) 4770.89 (0.01) 48.90 (0.31) 29.75 (0.99)1 shot and washing bLOD bLOD bLOD 20.02 (0.01) bLOD bLOD 12.02 (0.01) bLOD bLOD bLOD bLOD bLOD3 shots and washing 13.92 (0.01) bLOD bLOD 62.91 (2.75) bLOD bLOD 20.12 (0.02) bLOD bLOD 67.23 (0.29) 2.32 (1.37) bLOD5 shots and washing 33.25 (0.01) bLOD 9.64 (1.31) 163.44 (0.01) 3.47 (0.92) 24.81 (1.95) 87.52 (0.01) 8.01 (0.12) 17.89 (0.98) 160.86 (0.01) 4.71 (1.67) bLOD

109G.V

aninietal./Microchem

icalJournal115(2014)

106–112

† Numbers in parentheses represent the number of shots.

Fig. 4. 3D plots of Pb × Ba × Sb as a function of collection region: (a) palm; (b) back; (c) TF-palm; and (d) TF-back. Symbols corresponds to (●) blank; (○) man; (▼) woman; and(△) washing.

110 G. Vanini et al. / Microchemical Journal 115 (2014) 106–112

regions. Fig. 3 displays the right hand of the shooter holding theTaurus® .38 caliber handgun. The sequence of the shot and collectionprocedure was similar to that described in previous sections (1, 3 and5 shots, in triplicate); however, the washing step was not performed.A total of 20 samples (sum of the blank (2) with the number of shots(18)) were collected. Swabs containing GSRwere stored in 15 mL poly-propylene tubes. Then, 2 mL of HNO3 (10% (v/v)) and 8 mL of ultrapurewater were added to the samples. The samples were transferred to anultrasonic bath, agitated at 25 kHz for 20 min and heated in a waterbath for 1 h at 100 °C. Finally, the extracts were removed from thecentrifuge tube, diluted in 10 mL of deionized water and analyzed viaICP OES.

3. Results and discussion

3.1. Evaluating the best collection region of GSR on the hand of the shooter

Table 3 shows the Pb, Ba and Sb concentrations found in the fourhand regions analyzed (palm, back, TF-palm and TF-back). In all cases,

an increase in GSR concentration is observed as a function of the num-ber of shots (one, three and five). Lead was the element found to bemost abundant in both sexes (for men: from 21.99 (1)† to 255.07(5) μg L−1 for palm region; from 337.45 (1) to 1138.50 (5) μg L−1 forback region; from 336.30 (1) to 1913.80 (5) μg L−1 for TF-palm region;and from958.97 (1) to 5183.18 (5) μg L−1 for TF-back region). Lower Pbconcentrations were observed for women: from 38.22 (1) to 289.50(5) μg L−1 for palm region; from 187.82 (1) to 1049.25 (5) for backregion; from 357.97 (1) to 2145.78 (5) for TF-palm region; and from673.70 (1) to 4770.89 (5) μg L−1 for TF-back region. The higher concen-tration of Pb observed for men is due primarily to different physicalcharacteristics existing between male and female hands: male handsare larger, thicker and have more hair, which selectively contributes toa higher adhesion of the GSR.

When sensitivity is compared as a function of region, greater con-centrations of three elements (Pb, Ba and Sb) are mainly found on the

111G. Vanini et al. / Microchemical Journal 115 (2014) 106–112

back, TF-palm and the TF-back regions. However, when the effectof hand washing is analyzed, the three elements are only detected inthe TF-palm and the TF-back regions after three and five shots. TheTF-palm and the TF-back regionsweremore sensitive, providing resultsmore representative as a function of the number of shots and of handswashing [10]. This result is illustrated in Fig. 4c–d, which displays a 3Dplot of Pb × Ba × Sb.

3.2. Evaluating the best collector

Fig. 5 shows the Pb, Ba and Sb concentrations of GSRs sampled usingdifferent collectors with TF-palm and TF-back as collection points for 1,3 and 5 shots. In addition to the elements of interest (Pb/Ba/Sb), Al wasalso quantified using ICP OES because it is a potential interference in Pbmeasurement [22]. GSR and average Al concentrations were obtainedin triplicate and are shown in a 3D histogram as a function of thenumber of shots and number of hand washings. For blank analyses,Pb (14.14 μg L−1) and Ba (3.55 μg L−1) were detected in the double-sided collector, and Ba (1.06 μg L−1 and 7.61 μg L−1) was detected inthe adhesive collector (tape-type and plaster). In general, the tape-type collectors (with the exception of Scotch®)provided lower sensitiv-ity than the collector swabs (Fig. 5), and therefore, they were less suit-able for analysis. Note that for dry swabs and the Scotch ® collectors,no external contamination was observed for the elements Pb, Ba andSb. Among the collector swabs (dry, moistened with EDTA, and moist-ened with water), the dry swabs provided a better sensitivity for Pb,

Fig. 5. Pb, Ba and Sb concentrations of GSR in different collectors as a function of number of shTF-palm and TF-back regions.

Ba and Sb as a function of the number of shots considering the effectof hand washing (see the insert in Fig. 5). Additionally, the swab is acost effective, simple and rapid collection method because microwavepre-treatment is not necessary. The use of swabs for sampling GSR hasalso been reported in other papers [11,29]. When swabs are analyzedin the presence of EDTA, the sensitivity for Pb is increased [4,10]; how-ever, EDTA also acts as complexing agent for other elements, such as Al,which is detected in high concentrations (blank: 284 μg L−1; one shot:46 μg L−1; three shots: 72 μg L−1; andfive shots: 91 μg L−1) [30]. Finally,the Scotch® collector provides high sensitivity only for Pb andBa,wherethe presence of Sb was not detected (bLOD).

3.3. Evaluating the Pb, Ba and Sb concentrations on the left and right hands

Fig. 6 shows the average concentrations of Pb, Ba and Sb detected onthe left and right hands as a function of the number of shots. TheTF-palm and TF-back regions were sampled using dry swabs as the col-lection system. It was observed that there is an increase in the GSR con-centration as a function of the number of shots, which was observed asa higher concentration of Pb found on both hands.When comparing theGSR concentration between the left and right hands, Pb is mainly foundon the right hand, whereas the Ba and Sb concentrations are similar onboth hands. This difference is due to lower densities of these elements(Ba = 3510 kg m−3 and Sb = 6697 kg m−3) in relation to the Pb(11,340 kg m−3), thus allowing for a higher dispersion of particles.

ots (1, 3 and 5) and of the effect of hand washing. The collection was performed from the

0

100

200

300

400

500

600

700

800

900

Pb Ba Sb Pb Ba SbLeft hand Right hand

Co

nce

ntr

atio

n (

µg

L-1

)

1 shot

3 shots

5 shots

Fig. 6. Pb, Ba and Sb concentrations of GSR collected from left and right hands as a functionof the number of shots.

112 G. Vanini et al. / Microchemical Journal 115 (2014) 106–112

4. Conclusion

Inductively coupled plasma optical emission spectrometry (ICP OES)is a powerful tool for gunshot residue analysis, providingmultielementalquantification of lead (Pb), barium (Ba) and antimony (Sb)with limits ofdetection and quantification of 1.49 and 4.97 μg L−1 for Pb; 0.15 and0.50 μg L−1 for Ba; and 4.79 and 15.97 μg L−1 for Sb.

Pb, Ba and Sb were found in the four hand regions analyzed (palm,back, TF-palm and TF-back), and their concentrations increased as afunction of the number of shots (one, three and five). Pb was the mostabundant (with maxima concentrations of 5183.18 μg L−1 for themale shooter and 4770.89 μg L−1 for the female shooter). High sensitiv-ity ismainly observed on theback, TF-palm and the TF-back regions. Theeffect of hand washing was also evaluated, where the assay was able todetect the three elements at a concentration higher than 4.56mg L−1 onthe TF-palm and the TF-back regions. This behavior was observed onlyfor three and five shots. Among the collectors analyzed, swab collectors(dry, moistened with EDTA, and moistened with water) providedhigher sensitivity than tape-type collectors (adhesive, double-sidedand adhesive-plaster). Additionally, swabs are more cost effective asthey provide a simple and rapid collectionmethod that does not requiremicrowave digestion. Pb, Ba and Sb concentrations were also evaluatedon the left and right hands. It was observed that Pb is mainly found onthe right hand, whereas Ba and Sb concentrations are similar on both

hands due to the lower densities of Ba and Sb (Ba = 3510 kg m−3

and S = 6697 kg m−3) in relation to Pb (11,340 kg m−3), thus provid-ing a higher dispersion of particles.

Acknowledgments

The authors thank the Civil Police for their assistance with thegunshot residue collection experiments. GV acknowledges FAPES andCAPES for fellowships.

References

[1] D. Tocchetto, Balística Forense: Aspectos técnicos e jurídicos, 6th editionMillenniumeditor, São Paulo, Brazil, 2009.

[2] Ciência Forense: Balística, Available from: http://www.quimica.net 2007 (accessed18.09.13).

[3] O. Dalby, D. Butler, J.W. Birkett, J. Forensic Sci. 55 (2010) 924–943.[4] W. Romão, N.V. Schwab, M.I.M.S. Bueno, R. Sparrapan, M.N. Eberlin, A. Martyni, B.D.

Sabino, A.O. Maldaner. Quim. Nova 34 (2011) 1717–1728.[5] M.R. Bartsch, H.J. Kobus, K.P. Wainwright, J. Forensic Sci. 41 (1996) 1046–1051.[6] C. Sébastien, G. Nadia, Forensic Sci, Int. 216 (2012) 78–81.[7] A. Zeichner, N. Levin, M. Dvorachek. J. Forensic Sci. 36 (1990) 1020–1026.[8] F.S. Romolo, P. Margot, Forensic Sci. Int. 119 (2001) 195–211.[9] L. Moens, N. Jakubowski, Anal. Chem. News Features 70 (1998) 251–256.

[10] E.L.T. Reis, J.E.S. Sarkis, C. Rodrigues. Quim. Nova 27 (2003) 409–413.[11] A. Zeichner, N. Levin, J. Forensic Sci. 38 (1993) 571–584.[12] A. Zeichner, Anal. Bioanal. Chem. 376 (2003) 1178–1191.[13] R.E. Berk, J. Forensic Sci. 54 (2009) 69–76.[14] R.E. Berk, J. Forensic Sci. 54 (2009) 60–68.[15] E.F. Holly, J.W. Michael, J.G. Stuart, Forensic Sci. Int. 213 (2013) 88–91.[16] M.R. Rijnders, A. Stamouli, A. Bolck. J. Forensic Sci. 55 (3) (2010) 616–623.[17] M. Germani, J. Forensic Sci. 36 (1991) 331–342.[18] W.L. Tillman, J. Forensic Sci. 32 (1987) 62–71.[19] A. Martiny, A.P.C. Campos, M.S. Sader, A.L. Pinto, Forensic Sci. Int. 177 (2008) 9–17.[20] A. Berendes, D.Neimke, R. Schumacher,M.J. Barth, J. Forensic Sci. 51 (2006)1085–1090.[21] A. Ulrich, C.Moor, H. VonMont, H.R. Jordi, M. Loroy, Anal. Bioanal. Chem. 378 (2004)

1059–1068.[22] N. Yunes, S.Moyano, S. Cerutti, J.A. Gásquez, L.D.Martinez, Talanta 59 (2003) 943–949.[23] F.V. Silva, L.C. Trevizan, C.S. Silva, A.R.A. Nogueira, J.A. Nóbrega, Spectrochim. Acta B

57 (2002) 1905–1913.[24] D. Atanassova, V. Stefanova, E. Russeva, Talanta 47 (1998) 1237–1243.[25] V. Umashankar, R. Radhamani, K. Ramadoss, D. Murty, Talanta 57 (2002)

1029–1038.[26] C.F. Petry, Determination of Trace Elements in Environmental Samples by ICP OES,

32, Federal University of Rio Grande do Sul, Porto Alegre, 2005, pp. 42–43, (MSc inChemistry).

[27] L. Garofano, M. Capra, F. Ferrari, G.P. Brave, D. Di Tullio, M. Dell'Olio, A. Ghitti,Forensic Sci. Int. 103 (1999) 1–21.

[28] A.M. Dobney, W. Wiarda, P. De Joode, G.J.Q. Van Der Peijl, J. Anal. At. Spectrom. 17(2002) 478–484.

[29] L. Reid, K Chana, C. Chem, J.W. Bond, D.Phil. Matthew, J. Almond, S. Black. J. ForensicSci. 3 (2010) 753–756.

[30] M. Miyazawa, M.A. Pavan, Quim. Nova 15 (1992) 286–290