Protocol of the experiment: (adsorption of tnt on hair) july 15, 2002

Accummulation of Explosives in Hair
Jimmie C. Oxley,1 Ph.D.; James L. Smith,1 Ph.D.; Louis J. Kirschenbaum,1 Ph.D.; Kajal. P. Shinde,1 M.Sc.; and Suvarna Marimganti,1 B.Sc.
1Chemistry Department, University of Rhode Island, Kingston, RI 02881.
*This work was funded by Oklahoma City Memorial Institute for Prevention of Terrorism (MIPT).
ABSTRACT: The sorption of explosives [TNT, RDX, PETN, TATP, EGDN] to hair during
exposure to their vapors is examined. Three colors of hair were simultaneously exposed to explosive vapor. Following exposure of hair, the sorbed explosive was removed by extraction with acetonitrile and quantified. Results show that sorption of explosives, via vapor diffusion, to black hair is significantly greater than to blond, brown or bleached hair. Furthermore, the rate of sorption is directly related to the vapor density of the explosive: EGDN > TATP >>> TNT >> PETN > RDX. In some cases, the explosive-containing hair was subject to repeated washings with sodium dodecylsulfate or simply left out in an open area to determine the persistence of the explosive contamination. While explosive is removed from hair with time or washing, some persists. These results indicate that hair can be a useful indicator of explosive exposure/handling. KEYWORDS: forensic science, TNT, RDX, PETN, TATP, EGDN, hair, explosive sorption,
There is considerable evidence that drugs, metals and other chemicals are assimilated into hair as a result of ingestion and metabolic activity.1 This study documents the sorption to hair of explosives in the vapor phase. Since the mid-1900's researchers have been examining hair of laboratory animals and humans as evidence of exposure to chemicals.2-5 Hair has been shown to sorb heavy metals, pesticides, drugs (illicit and prescription), nicotine, and other chemicals which contaminate the environment (Table 1), but illicit drug detection appears to generate the most interest. While analysis of body fluids, i.e. blood and urine, provide unequivocal evidence of drug use, these methods are invasive. Furthermore, the elimination time is short; abstinence of only a few days reduces concentrations of drugs and their metabolites in body fluids to below detectable limits. In contrast, hair has been shown to retain drugs and their metabolites for many weeks following abstinence. The Society for Forensic Toxicology has accepted drug analysis of hair as a confirmatory technique, and the Substance Abuse and Mental Health Administration reviewed various factors pertinent to use of this technique as legal evidence.6,7 Hair testing has the advantages of being non-invasive, able to provide a historical record of exposure, resistant to countermeasures, and may offer a wider window of detection than analysis of body fluids.8-10 These advantages are evident from the suggestion that applicants for re-instatement of their driver's license in the province of Brescia, Italy be required to submit hair samples as proof of sustained abstinence from cocaine and heroin.11 Despite the advantages, there remains much controversy concerning detection of drugs in hair as evidence of drug usage. In addition to the presence of drugs and drug metabolites in the hair matrix that result from illicit use, drugs can be present after passive exposure.8 There is also evidence that assimilation is related to hair color and race.12-17 Hair color in humans and laboratory animals (rats and monkeys) appears to influence the extent to which drugs are sorbed, with dark hair picking up more than light hair. This is evident in a study where the subjects (rats) had both black and white hairs. The black hairs assimilated significantly more methadone than white.12 A number of studies have attempted to elucidate the sorption processes associated with the binding of drugs to hair. There is convincing evidence that drug-binding sites are associated with melanin granules, but the importance of other factors, such as hair lipid content, is a matter of some debate. One hypothesis is that hydrophobic interactions involving lipids binding non-polar organic substrates to hair play an important role. 18-21 Hair is composed of complex micro-environments and mechanisms by which it associates or assimilates substances are unclear. In this study the authors prefer to use the term "sorption" instead of more definitive terms such as "adsorption" or "absorption" to describe the interactions of explosives with hair because specific mechanisms by which explosives associate with hair have not been ascertained. The use of hair as evidence of exposure to explosives was pioneered by Wardleworth and Ancient of Royal Airforce Research and Development Establishment (RARDE), now British Defense Scientific and Technical Laboratory (dstl). They showed that nitrobenzene and ethylene glycol dinitrate (EGDN), both liquids with high vapor pressures, sorbed to bulk hair.22 With researchers at dstl, we initiated a preliminary study to evaluate the feasibility of detecting common military explosives in hair. Most military explosives are solids with very low vapor pressures. That study showed that both 2,4-dinitrotoluene and 2,4,6-trinitrotoluene (TNT, the most common filler of landmines) were readily sorbed by hair.23 The contamination of hair with explosives can occur by several modes—the interaction with explosive vapor, direct contact with explosive particles, or secondary contact involving direct transfer of particles from hands to hair. The study reported herein examined contamination of hair via vapor interaction only. This mode of exposure was chosen as a benchmark because it could be performed without the use of human subjects. Cut hair could be acquired by purchase or donation. A complimentary study is underway at dstl to examine particulate transfer to scalp hair of human subjects (The presence of explosive contamination is assessed by swabbing the hair with combs threaded with specially prepared gauze or cotton.). To examine explosive transfer to hair by vapor contact only, weighed quantities of hair were suspended over explosive powder. Four colors of hair were examined—black, brown, blond and bleached—though the majority of the studies focus on the first three. Five explosives were used—2,4,6-trinitrotoluene (TNT); hexahydro-1,3,5-trinitro-s- triazine (RDX, the active ingredient in C4); pentaerythritol tetranitrate (PETN, the explosive found in detonating cord and sheet explosives); ethylene glycol dinitrate (EGDN); and triacetone triperoxide (TATP, a homemade explosive recently figuring in a number of terrorist incidents). These explosives represent a broad range of volatilities. The sorption isotherms of TNT on the different colored hairs are reported. In addition, the persistence of explosive contamination on hair over time and after treatment with detergent was examined.
Exposure of Hair to Explosives Amber, glass, wide-mouth, screw-cap jars (10.5 cm diameter x 8.5 cm high) were washed with soap and water, rinsed with acetone, oven dried, and cooled to room temperature in a desiccator. Approximately, 0.5 g of explosive was placed in the bottom of the jar. Hair tresses, obtained from various sources, were washed by repeated rinsing with sodium dodecylsulfate. Each hair color was removed from its plastic storage bag with forceps, placed on clean paper, and cut into about 1.5-2.5 cm lengths with scissors. About 100 strands of this hair ( 0.3 g) were positioned on weighing paper (ends folded), weighed, and transferred to an aluminum foil weighing boat 1.5 cm in height and 6 cm in diameter. Three of these containers ("baskets") were strung vertically on an aluminum wire so that they would stack into the wide-mouth jar one above the other with sufficient space for air/vapor circulation. Generally, the oriental hair was in the top basket; the brown hair in the middle; and the blond hair in the bottom. During handling, care was taken that no contact was made between hair and other objects, particularly contact with the solid explosive on the bottom of the jar. The jars were stored in a fume hood in the laboratory, and the samples were incubated for various intervals. Quantification of Explosives Sorbed to Hair At the completion of the exposure time, the tier of baskets was removed from the explosive- exposure jar, and each hair type was placed on clean waxed paper where it was spread out and fluffed to mix inside and outside fibers. Each hair color was then divided into three portions of about 0.1 g each. Each portion, three for each of the three hair colors, was weighed into an amber, 16 mL, screw-cap bottle. None of the hair strands was allowed to touch the lid of the bottle. Acetonitrile (5.00 mL) was added, and the samples were sonicated for 20 minutes before they were placed on a shaker (speed 86 shakes/minute) for overnight extraction. After extraction, the acetonitrile was removed using a Pasteur pipette and about 1 mL of this solution was put in a 2 mL, septum screw- cap gas chromatograph (GC) vial (Initially, solution was filtered prior to placement in the vials; however, this step was later deemed unnecessary). The acetonitrile extracts were analyzed on a Hewlett Packard (HP) 5890 or an Agilent 6890N gas chromatograph (GC) using an electron capture detector (ECD) or micro-ECD, respectively. The column used was a J&W Scientific DB-5MS column [8 m x 0.53mm (megabore), film 1.5 um] (HP) or a HP-5 (20 m x 0.25mm, capillary column, Agilent). Details, including the injector and detector temperatures, initial and final oven temperatures, hold times and ramp rates, are shown below in Table 3. An external standard method was used to extracted samples quantify samples. Known concentrations of explosives were prepared in HPLC grade solvent (usually acetonitrile) and analyzed via GC or LC. Standard curves of area and height versus concentration for each explosive were constructed (using 5 points between 0.01 and 1.0 ppm). The correlation coefficients for the standard curves were better than 0.99. Both height and area data gave comparable results. The peak heights and/or areas for acetonitrile extracts of hair were used to extrapolate concentrations from the appropriate separately prepared standard curve. From the concentration and volume of extract plus mass of hair extracted, and it was possible to determine mass of explosive sorbed per gram of hair (µg/g). EGDN sorption was determined using high pressure liquid chromatography (HPLC). Analysis of 5uL samples was with a Hypersil BDS-C18 column (4.0 X 100 mm, 3-micron) and a mobile phase of 40% methanol in water. Quantification at 214 nm was with a photodiode array detector.
Persistence of Explosive in Hair Experiments described above show that hair sorbs explosive vapor. However, questions of retention are important to any potential forensic applications. These issues were addressed with several types of explosive-exposed hairs. Explosive-contaminated hair was divided into three portions ( 0.1 g each), and one or two portions were immediately analyzed to confirm the amount of explosive sorbed. The other portions were treated in one of the following ways. To examine persistence of the explosive in hair over time, portions of the hair were placed on clean watch glasses and allowed to stand in an explosive-free office (i.e. static air flow) for at least 2 days prior to analysis. The persistence of explosive upon washing of hair was evaluated as follows. A portion of the hair ( 0.1 g) was placed in 100 mL beakers with 0.5 mL of 2 % SDS solution. The mixture was stirred well with a glass rod. After a little water ( 5 mL) was added, the foam was decanted, and the procedure was repeated. The hair was then rinsed three times until no foam was visible. The hair was dried and extracted with acetonitrile as described above.
Results and Discussion
Sorption versus Position in Jars The baskets in the jars were different distances form the solid explosives. To determine whether ordering of the hair in the baskets made a difference, blond hair was placed in all three baskets and exposed to TATP for 24 hr. Results were similar to within experimental error (Table 2). Sorption versus Amount of Hair Four explosives were pure powders: TNT, PETN, RDX, TATP and one, EGDN, was a liquid. To determine whether the amount of hair in each basket affected the results, two exposure chambers were prepared in which each basket contained only a third as much hair (about 0.1 g) as was usually used. The results were similar to within experimental error, indicating reproducibility, and in correct proportion to hair exposed in 0.3 g portions for comparable periods of time.
Sorption Versus Chemical Composition of Explosive The literature reports that the occurrence of drugs in hair by users may be related to color. Our initial studies used black, blond and bleached hair. We found, like for drugs, that the black hair sorbed more chemical (in this case, TNT) than blond while bleached hair sorbed the least TNT. (Fig. 1) Three colors of hair, black (oriental), brown, and blond were exposed to TNT vapors for varying amounts of time in an attempt to determine at what concentration the hair was saturated. Table 4 shows micrograms of TNT observed on average of three runs for 10 time intervals. When these data are plotted (Fig. 2), it appeared that the hair was nearing saturation at 1800 hours (75d). For the brown and blond hair, sorption of TNT reached a maximum of 60 and 70 ug per gram hair, respectively, after about 1000 hours. In contrast, black oriental hair contained greater than 100 ug of TNT per gram hair and this was still increasing after 1000 hours. Much longer exposure times than those used for TNT were needed before significant quantities of PETN or RDX were detected. Table 5 indicates that in 5040 hours ( 7 months) the micrograms of PETN sorbed approached the same levels observed for the three colors of hair for TNT after 75 days. Table 6 shows that RDX sorption was substantially less; about 7 ug/gram hair (oriental) and about 2 ug/gram hair (brown and blond) after 5808 hours. Our hypothesis was that saturation levels of hair were comparable for every explosive, but the rates of achieving saturation were dramatically different. A different type of explosive, TATP, was used to test this hypothesis. The uptake of TATP was prompt and much more extensive. The apparent plateau of 100 ug per gram black hair for the NO2 functionalized explosives (TNT, RDX, PETN) was not observed for TATP (Table 7). TATP readily sorbed over 1000 ug/gram for black (oriental) hair within 48 hours. We reasoned that the high vapor pressure of TATP was related to the high rate of sorption. EGDN is a NO2 functionalized explosive with a relatively high vapor pressure. Table 8 indicates that sorption rate for EDGN was 21000 ug/gram for black (oriental) hair in 48 hours. Clearly, vapor pressure is an important, perhaps dominant criterion, for sorption of explosives to hair under the experimental conditions used in this study. Effect of Vapor Density on Sorption Vapor pressure data were available for TNT, RDX, PETN, and EGDN, but none had been reported for TATP. To further investigate the relationship between vapor pressure and sorption to hair we determined the vapor pressure of TATP. The vapor density of TATP in sealed containers, equilibrated at specified temperatures, was determined by injecting known volumes of vapor into a gas chromatograph with electron capture detection. Assuming ideal gas behavior, it was possible to calculate the vapor pressure. Vapor pressures were measured as a function of temperature and a Clapeyron plot, constructed. Details have been reported elsewhere.24 The vapor density of TNT was measured at the same time to confirm the applicability of the protocol used to determine the vapor pressure of TATP. The value determined for TNT was in agreement with those reported in the literature (Table 9). Thus, we have confidence in the value measured for TATP--0.03 mm at 25oC. Figure 3 illustrates time dependent uptake of various explosives. Not surprisingly rate of sorption appears directly related to available vapor of the explosive (room temperature vapor pressures in EGDN (0.07) > TATP(0.03) >>> TNT(4 x 10-6) >> PETN(2 x 10-8 ) > RDX(2 x 10-9).
The foregoing analysis presupposes that explosive vapors reach equilibrium with the solid within a short time. Various experiments, such as the similarity of uptake with different size samples (vide supra) or different size of containers, have convinced us that this is true.
Persistence of Explosives in Hair It was found that after standing in an explosive-free environment or being washed hair still retained a detectable amount of explosive (Table 10). Those with the highest vapor pressures, TATP and EGDN, were preferentially lost on standing. TNT, with a relatively low vapor pressure, was almost completely retained on standing, but significantly depleted upon washing. Since high retention in air was also expected with PETN, only the washing test was performed.
This study shows that hair is a viable surface from which explosive traces can be recovered. While contamination of hair may come by contact with explosive vapor or by particulate transfer— direct or indirect (e.g. hands transfer to hair), this study specifically examined vapor transfer. It showed that even explosives with extremely low vapor pressure (i.e. RDX) may be sorbed by hair. The sorbed explosive persists on the hair. Simply standing in air, TATP, EGDN and TNT remained on hair up to two days; and TNT, up to six days. (Six days was the maximum standing time allowed since it was assumed after six days, head hair would be washed.) It is likely that similar persistence in air will be observed for PETN and RDX. A more rigorous test of persistence is washing. Though explosive sorbed by hair was susceptible to removal during washing, laboratory washings showed that some explosives persisted through up to three (TATP, EGDN, PETN) and six (TNT) rinses. Since frequency and mode of hair washing varies dramatically among individuals, there is the possibility that explosive residues will persist in hair for days after exposure. Preliminary results from the dstl Forensic Explosive Laboratory with subjects who handle explosives suggest that particulate transport is even more significant than vapor deposition. Indeed some workers, who reportedly washed their hair after a day of exposure to explosives, were still found contaminated the following day.
The shapes of the curves in Figure 2 suggest an adsorption mechanism for describing the interaction of TNT vapor with hair. However, hair is a complex matrix consisting of myriad micro- environments. These preliminary results do not provide sufficient evidence for us to fully speculate on mechanisms of interaction between explosives and hair.
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Additional information and reprint requests:Jimmie C. OxleyChemistry DepartmentUniversity of Rhode IslandKingston, RI 02881Phone/fax:401-874-2103E-mail: Table 1: Chemicals Known to be Sorbed to Hair Table 2: Blond Hair Exposed to TATP 24 hr Table 3: GC Analysis Conditions Table 4: TNT Sorbed to Hair ug TNT/g Hair (GC Analysis by Area). Standard deviations are indicated in parentheses.
Table 5: PETN (ug)/g Hair Table 6: RDX (ug)/g Hair Table 7: TATP (ug)/g Hair Table 8: EGDN (ug)/g Hair. The Demeo Brown hair (for scientific purposes) was purchased from Demeo Brothers, NY Table 9: Values for TNT and TATP Vapor Pressure Table 10: Persistence Table1: Chemicals Known to be Sorbed to Hair Blond Hair Exposed to TATP 24 hr ug/g hair average ug std dev Table 3: GC Analysis Conditions Volume Temperture Temperture Temperture Hold Time Temperature Final Hold Retention Time (min) Time (min) TATP vapor@ split 125:1 * Analyses performed on HP 5890 GC with DB-5MS column; all others used Agilent 6890N with HP-5 column.
TNT Sorbed to Hair ug TNT/g Hair (GC Analysis by area)
hair hours
91 std dev
144 std dev
192 std dev 220 std dev 380 std dev 500
504 std dev 648 std dev 1800 std dev
PETN (ug)/g Hair
hair hours 1848
RDX (ug)/g Hair
TATP (ug)/g Hair
hair hours
EGDN (ug/g) Hair
Values for TNT & TATP Vapor Pressure log 10P(mmHg) = A-[B/T(K)] for all data except Cundall, 1978 where the A and B values compute as logeP with P in units of Pascal. The value in Pascal units is converted to mm Hg in this table. % Retained on Standing in Air 48 h % Retained on 3 Washes of 2% SDS Percent of explosive retained is relative to the ug of explosive (per gram hair) of the sample after exposure to explosive but before standing or washing (shown in upper table).
TNT in Hair after 144 hr Exposure Time, Hours
-- PETN --
-- TATP/10--
- EGDN/10-
Figure 1: TNT uptake by hair Figure 2: Sorption of TNT by Black, Brown, & Blond Hair over Time Figure 3: Sorption of Various Explosives vs. Time (TATP & EGDN values were divided by 10)


seems always to be the woman. This probably relates to the X-chromosomal localization of DCX. 1. des Portes V, Pinard JM, Billuart P, et al. A novel CNS gene required Our study has important implications for genetic for neuronal migration and involved in X-linked subcortical laminar counseling of families with SBH/XLIS patients. Ow- heterotopia and lissencephaly syndrome. Cell 1998;92:51– 61.

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