In the Laboratory
Using Laboratory Chemicals To Imitate Illicit Drugs in a Forensic Chemistry Activity Shawn Hasan, Deborah Bromfield-Lee, Maria T. Oliver-Hoyo,* and Jose A. Cintron-Maldonado Department of Chemistry, North Carolina State University, Raleigh, NC 27695; *
[email protected] Research has shown that hands-on applications of chemistry to the solution of real problems stimulate students’ interest (1, 2). One particular area that sparks student motivation and enthusiasm for the course material is forensic science (2–5). Forensic chemistry is essentially the application of chemistry to law-related matters. Taking into consideration that inquirybased activities and active-learning environments not only create interest, but also may help students learn more effectively and develop independent learning skills (6, 7), we developed a new inquiry-based activity that recreates the work of a forensic chemist. This activity builds upon traditional drug-identification tests by including presumptive forensic testing procedures and incorporating laboratory chemicals that produce screening results similar to controlled substances. The forensic approach to chemistry encourages students to obtain accurate results with cautious interpretations because of the implications involved with an incorrect determination (proving someone’s innocence or guilt). The identification of drugs of abuse is the most prominent area in forensics that involves chemistry (8, 9). The scheme of analysis used by a forensic chemist typically involves subjecting an unknown drug sample to a series of screening (presumptive) tests followed by a confirmatory test. Each technique has a unique degree of discriminating power, set forth by the Scientific Working Group for the Analysis of Seized Drugs (10). Examples of the common techniques performed for the analysis of drugs, in order of decreasing discriminating power from A to C, are shown in Table 1. When a category A (confirmatory) technique is incorporated into the analytical scheme, then at least one other technique (from either category A, B, or C) must be used. If a category A technique is not used, then at least three different validated methods from B or C should be employed. The results from category A and B techniques must be reviewable (printed spectra, chromatograms, photocopies of TLC plates, etc.). These are the recommended minimum standards for the forensic identification of drugs of abuse. For this activity, chemical spot tests (CSTs) and thinlayer chromatography (TLC) were chosen due to their simplicity, versatility (11), common use by forensic chemists
(12–17), availability, and low cost of the reagents and equipment needed. CSTs are microscale color reactions that allow for quick qualitative testing across a broad range of inorganic and organic substances. Forensic chemists use TLC to run many samples in parallel (qualitatively) or two-dimensionally (quantitatively) (13). The general procedure is to develop a second TLC plate with the suspected material alongside an authentic or standard sample (9). If both the known and unknown have the same Rf values, a tentative identification can be made (9, 16). Because the possibility of distinguishing hundreds of basic drugs from one another simply by their Rf values is improbable (9, 18), TLC is only selected after a series of CSTs are performed. Forensic Activity The focus of this activity is drug identification techniques since the majority of evidence analyzed by a forensic chemist comes from drug-related crimes (9). This activity includes the following learning objectives: (i) to explain how simple color reactions can screen for illicit drugs; (ii) to describe how TLC can be used to separate and tentatively identify drugs; (iii) to predict how polarity changes affect TLC results, and (iv) to explain why CSTs and TLC serve for screening purposes only. Actual scenarios promote creativity, which has been shown to increase both participation and the desire to learn about analytical techniques (19). Therefore, students are first introduced to the activity with a fictitious scenario detailing how the ten drug samples were confiscated during a warehouse raid (see the online supplement). For obvious reasons, obtaining heavily regulated controlled substances to create an undergraduate student activity is not practical for most educational institutions. This is primarily the reason why most traditional experiments in this area have focused on common over-the-counter (OTC) analgesic analysis using TLC. Only recently has the use of OTC chemicals and CSTs been investigated for instructional laboratory development (20, 21). We were able to identify OTC and laboratory chemicals that mimic actual street drugs in terms of physical properties and
Table 1. Categories of Analytical Techniques Category A
Category B
Category C
Infrared spectroscopy
Gas chromatography
Chemical spot tests
Mass spectrometry
Liquid chromatography
Fluorescence spectroscopy
Nuclear magnetic resonance spectroscopy
Microcrystalline tests
Ultraviolet spectroscopy
Raman spectroscopy
Thin-layer chromatography
Melting point
Pharmaceutical identifiers
Immunoassay
Ion mobility spectrometry Note: The categories are from ref 10.
© Division of Chemical Education • www.JCE.DivCHED.org • Vol. 85 No. 6 June 2008 • Journal of Chemical Education
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In the Laboratory
color response. Using these selected chemicals, the focus of the activity is on the screening aspect of drug testing, which provides students with the opportunity to understand what obstacles a forensic chemist faces when analyzing a sample of unknown identity. This activity aims to foster independent analytical and logical-thinking skills as students utilize forensic techniques to solve a real-world problem. Selected Laboratory Chemicals as Mock Drugs Five chemicals were identified that produced results mimicking illicit drugs in physical appearance, chemical availability (unregulated), value (low cost), and color-reaction results (associated color and response factor). Mock drugs used in this activity include the laboratory chemicals chlorpromazine HCl (for heroin: opiates) (11, 12, 22), methapyrilene HCl (for cocaine: stimulants) (23), 2-chloroacetophenone (for mescaline: hallucinogen) (11, 22), and indole (for LSD: hallucinogen) as well as the OTC drug Benadryl or diphenhydramine HCl (for cocaine) (21). In addition, other common OTC drugs were included to provide students with negative test results such as different forms of analgesics (aspirin, Tylenol, ibuprofen, and Excedrin). The information inherent in obtaining a negative response should not be overlooked. If a student observes a negative response, it is reasonable for them to assume that illicit drugs are not present or in quantities below the usual ingested drug quantities (24). Experimental Procedure Students collect data from the reactions of ten chemicals (laboratory and OTC) with five chemical spot test reagents typically found in the crime laboratory. Laboratory grade and OTC chemicals are purchased in crystal, powder, tablet, or capsule form. Capsules are split open and tablets crushed into a fine powder before testing. Two drops of CST reagent are added with a Pasteur pipet to each of four wells on a porcelain test plate. If there is no reaction after a few seconds elapse, contamination in the porcelain test plate is ruled out. Quantities in the order of 100–500 μg of each analyte are then added and allowed to react for 5 minutes before the final color is noted. The scheme shown in Figure 1 effectively mimics five illicit drugs using CSTs and differentiates the mock drugs from the other OTC chemicals. The selected chemicals provide students with positive and negative responses to each of the five CSTs. This introduces the concept of false positives in a forensic testing scheme. The TLC system ethyl ether:methanol (90:10), similar to the system developed by Clarke (16), provides a spread of Rf values with high reproducibility for the ten selected chemicals in this activity. This allows students to tentatively identify all of the materials tested in the first portion of the activity by CSTs. Solutions of 1 mg/mL in ethyl ether are stored in 1-dram vials (~4 mL capacity) on a lab bench and are stable for two weeks under these conditions. The ten compounds are effectively separated based on their affinity towards the ethyl ether:methanol mobile phase. Spotted TLC plates are examined under both shortwave and longwave UV light to ensure an adequate quantities of starting material is present. Developed plates are placed in a fume hood and allowed to dry for 2 minutes. The plates are examined under UV light, marked lightly, and then placed
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in an iodine chamber. The use of both UV light and an iodine chamber can distinguish between samples with close Rf values, since substances chosen do not have similar reactions to the iodine or light. Hazards Very small quantities of chemicals are used in this activity, however, all reagents and chemicals should be handled with gloves under adequate ventilation. Some reagents contain small quantities of either concentrated sulfuric acid (hygroscopic) or nitric acid (strong oxidizer). Chlorpromazine HCl, methapyrilene HCl, indole, stannous chloride, selenous acid, ammonium vanadate, and cobalt thiocyanate are hazardous in case of inhalation, skin contact (irritant, permeator), eye contact (irritant), and ingestion. 2-Chloroacetophenone is a lachrymator. Formaldehyde is a suspected human carcinogen and flammable. It is harmful if inhaled or absorbed through the skin and is an eye and skin irritant. Diethyl ether is flammable, an irritant, and an anesthetic by inhalation. Methanol is a flammable liquid that may cause skin and eye irritation. Iodine is a corrosive oxidant with irritant vapors and it must be stored away from combustible materials, strong acids, metals, and reducing agents. Safety goggles, disposable nitrile gloves, and standard laboratory apparel must be worn at all times. UV rays may be harmful to unprotected eyes and skin. Chemical spot tests and TLC should be performed in a hood. Hazardous waste should be deposited in designated and labeled containers. Conclusion The described forensic activity utilizes two common forensic presumptive techniques to justify further confirmatory testing on mock illicit samples. Throughout the activity, students learn about the non-specific nature of CSTs, the strengths of combining CSTs and TLC techniques for forensic screening, the challenges in forensic chemistry when analyzing samples of unknown identity, and the relevance of false positives in a forensic testing scheme. This hands-on forensic activity provides educators with an opportunity to expose students to the techniques used by the modern forensic chemist for drug screening. Students who conducted this experiment were able to perform the procedures and attain the learning goals of the experiment. We identified OTC and laboratory chemicals that mimic actual street drugs in terms of physical properties and color response using CSTs. The scheme we developed effectively differentiates the mock drugs from the other chosen OTC chemicals. These selected chemicals allow the student to explore the screening aspect of drug testing. In addition, the selected chemicals provide students with positive and negative responses to each of the five CSTs. Confirmatory testing techniques can be combined with this presumptive activity to both qualitatively and quantitatively analyze the sample. Interpreting and comparing spectra of drugs is critical in crime laboratory analysis (8). Although drug-testing experiments involving TLC have been thoroughly described in the literature (25–29), the combination of using CSTs and TLC for a forensic activity has not. The incorporation of these techniques in an activity provides students with a more discriminating procedure.
Journal of Chemical Education • Vol. 85 No. 6 June 2008 • www.JCE.DivCHED.org • © Division of Chemical Education
© Division of Chemical Education • www.JCE.DivCHED.org • Vol. 85 No. 6 June 2008 • Journal of Chemical Education
codeine
orange
Figure 1. CST scheme.1
heroin
yellow
(á)
(ź)
any other color
heroin
red
not illicit material
morphine
red
nitric acid
violet
codeine
olive– gray
positive (á)
codeine
olive– gray
(á)
amphetamine
Mandelin
any other color
(ź)
any other
(ź)
test for barbiturates
methcolor amphetamine
blue–green
mescaline
yellow– green
LSD
Mecke’s
any other color
( ź)
light tan– olive
(á)
cobalt thiocyanate
green– black
psylocybin
green
heroin
red
(á)
any other color
negative (ź)
cocaine
blue w/solid
not illicit material
any other color
(ź)
methamphetamine
blue–green
Mandelin
amphetamine
yellow– green
(á)
reddish tones
Marquis
unknown
In the Laboratory
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In the Laboratory
Note 1. Marquis reagent is composed of a mixture of formaldehyde and concentrated sulfuric acid; Mandelin’s reagent is a solution of ammonium vanadate in sulfuric acid; and Mecke’s reagent is selenious acid dissolved in concentrated sulfuric acid.
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17. Macherone, A. J.; Siek, T. J. J. Chem. Educ. 2000, 77, 366–367. 18. Coumbis, R. J.; Fulton, C. C.; Calise, J. P.; Rodriguez, C. J. Chrom. 1971, 54, 245–250. 19. Bender, S.; Lillard, S. J. J. Chem. Educ. 2003, 80, 437–440. 20. Anderson, J. J. Chem. Educ. 2005, 82, 1809–1810. 21. Lawrence, J. K. Workshop in Forensic Chemistry; Center for Workshops in Chemical Sciences: 2004. See also http://www. williams.edu/Chemistry/lkaplan/ (accessed Feb 2008). 22. U.S. Department of Justice. NILECJ Standard for Chemical Spot Test Kits for Preliminary Identification of Drugs of Abuse; U.S. Department of Justice: Washington, DC, July 2000. 23. Masoud, A. N. J. Pharm. Sci. 1975, 64, 841–844. 24. Velapoldi, R. A.; Wicks, S. A. J. For. Sci. 1974, 19, 636–656. 25. Jellin E. E. Western Carolina University, Chemistry and Physics. http://paws.wcu.edu/jellen/6.pdf (accessed Feb 2008). 26. Cawley, J. J J. Chem. Educ. 1995, 72, 272–273. 27. Bonicamp, J. M. J. Chem. Educ. 1985, 61, 160–161. 28. Martin, N. H. J. Chem. Educ. 1981, 58, 818–819. 29. Cormier, R. A.; Hudson, W. B.; Siegal, J. A. J. Chem. Educ. 1979, 56, 180.
Supporting JCE Online Material
http://www.jce.divched.org/Journal/Issues/2008/Jun/abs813.html Abstract and keywords Full text (PDF) Links to cited URLs and JCE articles Supplement Student handouts
Instructor notes
JCE Featured Molecules for June 2008 (see p 880 for details) Structures of some of the molecules discussed in this article are available in fully manipulable Jmol format in the JCE Digital Library at http://www.JCE.DivCHED.org/JCEWWW/Features/ MonthlyMolecules/2008/Jun/.
Journal of Chemical Education • Vol. 85 No. 6 June 2008 • www.JCE.DivCHED.org • © Division of Chemical Education
