forensic drug testing and analysis.pdf

Introduction The purposes of drug testing by the criminal justice system for persons who have recently ingested a drug, to identify users, to monitor and deter drug use, and to estimate national druguse trends in criminals. Substantial work has been reliability and methodology of drug-testing technologies. justice system tests involve urinalysis. Experimental research on radioimmunoassay of hair samples. Much discussion system drug testing focuses on pretrial drug testing, the Use Forecasting program, and the testing of juvenile detainees. offenders typically began their drug use in their early teens, testing of juvenile detainees may provide the most effective detection and prevention of drug abuse in a high-risk population. testing of persons detained or monitored by the criminal raises a number of critical legal and ethical issues that differ raised by testing other. A drug can be defined as a natural or synthetic substance that is used to produce physiological or psychological effects in humans or other animals. However, criminalists are concerned primarily with a small number of drugs many of them illicit that are commonly used for their intoxicating effects. These include marijuana, the most widely used illicit drug in the United States, and alcohol, which is consumed regularly by 90 million Americans. Drug abuse has grown from a problem generally associated with members of the lower end of the socioeconomic ladder to one that cuts across all social and ethnic classes of society. Today, approximately 23 million people in the United States use illicit drugs. Because of the epidemic proportions of illegal drug use, more than 75 percent of the evidence evaluated by crime laboratories in the United States is drug related . The deluge of drug specimens has necessitated the expansion of existing crime laboratories and the creation of new ones. For many concerned forensic scientists, the crime laboratory’s preoccupation with drug evidence represents a serious distraction that takes time away from evaluating evidence related to homicides and other types of serious crimes. However, the increasing caseloads associated with drug evidence have justified the expansion of forensic laboratory services. This expansion has increased the overall analytical. capabilities of crime laboratories. 1 Drug testing is a key component of drug court programs because it provides readily available and objective information to the judge, other justice system officials, treatment personnel, and caseworkers regarding a participant’s progress in treatment. The drug testing process, coupled with immediate program responses, forces defendants to address their substance abuse problems immediately and continuously. Every professional discipline requires professionally trained individuals. Forensic drug testing is no exception. Drug testing is a complex science and requires the support of a forensic expert regardless of the testing method that is used. As with any scientific test, the interpretation of a drug test result requires balancing a number of factors, including elements directly related to the test, the physical characteristics of the individual being tested, and the nature and length of the individual’s drug usage. The value and usefulness of a drug testing regime are dependent on the scientific integrity of the drug testing process and the accurate interpretation and assessment of the raw data. This is not to say that every program must hire a pathologist or certified lab technician to interpret test results. However, every court should have technical support, which is generally available from the drug testing/chemical companies that provide equipment, supplies, and training in this area. To reduce demand for drugs, people must be deterred or dissuaded from initiating drug use, and persons who already use illicit drugs must be induced to cease. Drug-abuse education, prevention, and treatment programs and some law-enforcement actions are interventions intended to accomplish these goals. In the past fifteen years, with the development of cost effective technology for measuring chemical markers of drug use in the body, a new strategy of identification through drug testing has become available for reducing demand for drugs. Knowledge that one may be tested for drugs may deter persons from initiating use, and the testing itself can identify current users for referral to treatment, to periodic urine monitoring, or to other interventions. Drug testing has been embraced more by government agencies, private corporations, the military, and drug treatment programs than by criminal justice agencie . 2 Drug Dependence In assessing the potential danger of drugs, society has become particularly conscious of their effects on human behavior. In fact, the first drugs to be regulated by law in the early years of the twentieth century were those deemed to have “habit-forming” properties. The early laws were aimed primarily at controlling opium and its derivatives; cocaine; and, later, marijuana. The ability of a drug to induce dependence after repeated use is submerged in a complex array of physiological and social factors. Dependence on different drugs exists in numerous patterns and in all degrees of intensity, and depends on the nature of the drug, the route of administration, the dose, the frequency of administration, and the individual’s rate of metabolism. Furthermore, nondrug factors play an equally crucial role in determining the behavioral patterns associated with drug use. The personal characteristics of the user, his or her expectations about the drug experience, society’s attitudes toward and possible responses to the drug, and the setting in which the drug is used are all major determinants of drug dependence. The questions of how to define and measure a given drug’s influence on the individual and its danger to society are difficult to assess. The nature and significance of drug dependence must be considered from two overlapping points of view: the interaction of the drug with the individual, and the drug’s impact on society. It will be useful to approach the problem from two distinctly different aspects of human behavior: psychological dependence and physical dependence. Psychological Dependence The common denominator that characterizes all types of repeated drug use is psychological dependence on continued use of the drug. It is important to discard the unrealistic image that all drug users are hopeless “addicts” who are social dropouts. Most users present a quite normal appearance and remain both socially and economically integrated into the life of the community. The reasons some people abstain from drugs while others become moderately or heavily involved are difficult if not impossible to delineate. Psychological needs arise from numerous personal and social factors that inevitably stem from the individual’s desire to create a sense of well-being and to escape from reality. 3 In some cases, the individual may seek relief from personal problems or stressful situations or may be trying to sustain a physical and emotional state that permits an improved level of performance. Whatever the reasons, the underlying psychological needs and the desire to fulfill them create a conditioned pattern of drug abuse. . The intensity of the psychological dependence associated with a drug’s use is difficult to define and largely depends on the nature of the drug. For drugs such as alcohol, heroin, amphetamines, barbiturates, and cocaine, continued use will probably result in a high degree of involvement. Other drugs, such as marijuana and codeine, appear to have a considerably lower potential for the development of psychological dependence. However, this does not imply that repeated abuse of drugs deemed to have a low potential for psychological dependence is safe or will always produce low psychological dependence. We have no precise way to measure or predict the impact of drug abuse on the individual. Even if a system could be devised for controlling the many possible variables affecting a user’s response, the unpredictability of the human personality would still come into play. Our general knowledge of alcohol consumption Physical Dependence Although emotional well-being is the primary motive leading to repeated and intensive use of a drug, certain drugs, taken in sufficient dose and frequency, can produce physiological changes that encourage their continued use. Once the user abstains from such a drug, severe physical illness follows. The desire to avoid this withdrawal sickness, or abstinence syndrome, ultimately causes physical dependence, or addiction. Hence, for the addict who is accustomed to receiving large doses of heroin, the prospect of abstaining and encountering the resulting body chills, vomiting, stomach cramps, convulsions, insomnia, pain, and hallucinations is a powerful inducement for continuing to use. Interestingly, some of the more widely abused drugs have little or no potential for creating physical dependence. Drugs such as marijuana, LSD, and cocaine create strong anxieties when their repeated use is discontinued; however, no medical evidence attributes these discomforts to physiological reactions that accompany withdrawal sickness. On the other hand, use of alcohol, 4 heroin, and barbiturates can result in the development of physical dependence. Physical dependence develops only when the drug user adheres to a regular schedule of drug intake; that is, the interval between doses must be short enough so that the effects of the drug never wear off completely. For example, the interval between injections of heroin for the drug addict probably does not exceed six to eight hours. Beyond this time the addict will begin to experience the uncomfortable symptoms of withdrawal. Many users of heroin avoid taking the drug on a regular basis for fear of becoming physically addicted to its use. Similarly, the risk of developing physical dependence on alcohol becomes greatest when the consumption is characterized by a continuing pattern of daily use in large quantities. Societal Aspects of Drug Use The social impact of drug dependence is directly related to the extent to which the user has become preoccupied with the drug. Here, the most important element is the extent to which drug use has become interwoven in the fabric of the user’s life. The more frequently the drug satisfies the person’s need, the greater the likelihood that he or she will become preoccupied with its use, with a consequent neglect of individual and social responsibilities. Personal health, economic relationships, and family obligations may all suffer as the drug-seeking behavior increases in frequency and intensity and dominates the individual’s life. The extreme of drug dependence may lead to behavior that has serious implications for the public’s safety, health, and welfare. Drug dependence in its broadest sense involves much of the world’s population. As a result, a complex array of individual, social, cultural, legal, and medical factors ultimately influence society’s decision to prohibit or impose strict controls on a drug’s distribution and use. Invariably, society must weigh the beneficial aspects of the drug against the ultimate harm its abuse will do to the individual and to society as a whole. Obviously, many forms of drug dependence do not carry sufficient adverse social consequences to warrant their prohibition, as illustrated by the widespread use of such drug-containing substances as tobacco and coffee. Although the heavy and prolonged use of these drugs may eventually damage body organs and injure an individual’s health, there is no evidence that they result in antisocial behavior, even with prolonged or excessive use. 5 Hence, society is willing to accept the widespread use of these substances. We are certainly all aware of the disastrous failure of the United States’ prohibition of alcohol use during the 1920s and also of the current debate on whether marijuana should be legalized. Each of these issues emphasizes the delicate balance between individual desires and needs and society’s concern with the consequences of drug abuse; moreover, this balance is continuously subject to change and reevaluation. Table 1: The potential of some commonly abused drugs to produce dependence with regular use . 6 Collection and preservation of drug evidence Preparation of drug evidence for submission to the crime laboratory is normally relatively simple and accomplished with minimal precautions in the field. The field investigator must ensure that the evidence is properly packaged and labeled for delivery to the laboratory. Considering the countless forms and varieties of drug evidence that are seized, it is not practical to prescribe any single packaging procedure for fulfilling these requirements. Generally, common sense is the best guide in such situations, keeping in mind that the package must prevent loss and/or crosscontamination of the contents. Often, the original container in which the drug was seized will meet these requirements. Specimens suspected of containing volatile solvents, such as those involved in glue-sniffing cases, must be packaged in an airtight container to prevent evaporation of the solvent. All packages must be marked with sufficient information to ensure identification by the officer in future legal proceedings and to establish the chain of custody. To aid the drug analyst, the investigator should supply any background information that may relate to a drug’s identity. Analysis time can be markedly reduced when the chemist has this information. For the same reason, the results of drug-screening tests used in the field must also be transmitted to the laboratory. However, although these tests may indicate the presence of a drug and may help the officer establish probable cause to search and arrest a suspect, they do not offer conclusive evidence of a drug’s identity. Forensic drug analysis and testing One only has to look into the evidence vaults of crime laboratories to appreciate the assortment of drug specimens that confront the criminalist. The presence of a huge array of powders, tablets, capsules, vegetable matter, liquids, pipes, cigarettes, cookers, and syringes is testimony to the vitality and sophistication of the illicit-drug market. If outward appearance is not evidence enough of the United States in 1971. In 1972, production quotas were established reducing amphetamine production approximately 80 percent below 1971 levels. 7 The criminal penalties for the unauthorized manufacture, sale, or possession of controlled dangerous substances are related to the schedules as well. The most severe penalties are associated with drugs listed in schedules I and II. For example, for drugs included in schedules I and II, a first offense of individual trafficking is punishable by up to twenty years in prison and/or a fine of up to $1 million for an individual or up to $5 million for other than individuals. The table summarizes the control mechanisms and penalties for each schedule of the Controlled Substances Act. The Controlled Substances Act also stipulates that an offense involving a controlled substance analog a chemical substance substantially similar in chemical structure to a controlled substance triggers penalties as if it were a controlled substance listed in schedule I. This section is designed to combat the proliferation of so-called designer drugs substances that are chemically related to some controlled drugs and are pharmacologically very potent. These substances are manufactured by skilled individuals in clandestine laboratories with the knowledge that their products will not be covered by the schedules of the Controlled Substances Act. For instance, fentanyl is a powerful narcotic that is commercially marketed for medical use and is also listed as a controlled dangerous substance. This drug is about one hundred times as potent as morphine. A number of substances chemically related to fentanyl have been synthesized by underground chemists and sold on the street. The first such substance we know of was sold under the street name China White. These drugs have been responsible for more than a hundred overdose deaths in California and nearly twenty deaths in western Pennsylvania. As designer drugs such as China White become identified by drug officials and linked to drug abuse, they are placed in appropriate schedules. When a forensic chemist picks up a drug specimen for analysis, he or she can expect to find just about anything, so all contingencies must be prepared for. The analysis must leave no room for error because its results will have a direct bearing on the process of determining the guilt or innocence of a defendant. There is no middle ground in drug identification either the specimen is a specific drug or it is not and once a positive conclusion is drawn, the chemist must be prepared to support and defend the validity of the results in a court of law. 8 Screening and Confirmation The challenge or difficulty of forensic drug identification comes in selecting analytical procedures that will ensure a specific identification of a drug. Presented with a substance of unknown origin and composition, the forensic chemist must develop a plan of action that will ultimately yield the drug’s identity. This plan, or scheme of analysis, is divided into two phases. First, faced with the prospect that the unknown substance may be any one of a thousand or more commonly encountered drugs, the analyst must employ screening tests to reduce these possibilities to a small and manageable number. This objective is often accomplished by subjecting the material to a series of color tests that produce characteristic colors for the more commonly encountered illicit drugs. Even if these tests produce negative results, their value lies in having excluded certain drugs from further consideration. Once the number of possibilities has been reduced substantially, the second phase of the analysis must be devoted to pinpointing and confirming the drug’s identity. In an era in which crime laboratories receive voluminous quantities of drug evidence, it is impractical to subject a drug to all the chemical and instrumental tests available. Indeed, it is more realistic to look on these techniques as constituting a large analytical arsenal. The chemist, aided by training and experience, must choose tests that will most conveniently identify a particular drug. 9 Forensic chemists often use a specific test to identify a drug substance to the exclusion of all other known chemical substances. A single test that identifies a substance is known as a confirmation. The analytical scheme sometimes consists of a series of nonspecific or presumptive tests. Each test in itself is insufficient to prove the drug’s identity; however, the proper analytical scheme encompasses a combination of test results that characterize one and only one chemical substance the drug under investigation. Furthermore, experimental evidence must confirm that the probability of any other substance responding in an identical manner to the scheme selected is so small as to be beyond any reasonable scientific certainty. Another consideration in selecting an analytical technique is the need for either a qualitative or a quantitative determination. The former relates just to the identity of the material, whereas the latter refers to the percentage of each component in the mixture. Hence, a qualitative identification of a powder may reveal the presence of heroin and quinine, whereas a quantitative analysis may conclude the presence of 10 percent heroin and 90 percent quinine. Obviously, a qualitative identification must precede any attempt at quantitation; there is little value in attempting to quantitate a material without first determining its identity. Essentially, a qualitative analysis of a material requires the determination of numerous properties using a variety of analytical techniques. On the other hand, a quantitative measurement is usually accomplished by precise measurement of a single property of the material. Forensic chemists normally rely on several tests for a routine drug identification scheme: color tests, microcrystalline tests, chromatography, spectrophotometry, and mass spectrometry.. Color Tests Many drugs yield characteristic colors when brought into contact with specific chemical reagents. Not only do these tests provide a useful indicator of a drug’s presence, but they are also used by investigators in the field to examine materials suspected of containing a drug . However, color tests are useful for screening purposes only and are never taken as conclusive identification of unknown drugs. Five primary color-test reagents are as follows: 10 1. Marquis. The reagent turns purple in the presence of heroin and morphine and most opium derivatives. Marquis becomes orange-brown when mixed with amphetamines and methamphetamines. 2. Dillie-Koppanyi. This is a valuable screening test for barbiturates, in whose presence the reagen turns a violet-blue color. 3. Duquenois-Levine. This is a valuable color test for marijuana, performed by adding a series of chemical solutions to the suspect vegetation. A positive result is shown by a purple color when chloroform is added. 4. Van Urk. The reagent turns blue-purple in the presence of LSD. However, owing to the extremely small quantities of LSD in illicit preparations, this test is difficult to conduct under field conditions. 5. Scott Test. This is a color test for cocaine. A powder containing cocaine turns a cobalt thio cyanate solution blue. Upon the addition of hydrochloric acid, the blue color is transformed to a clear pink color. Upon the addition of chloroform, if cocaine is present, the blue color reappears in the chloroform layer. Figure 01 A field color-test kit for cocaine. The suspect drug is placed in the plastic pouch. Tubes containing chemicals are broken open, and the color of the chemical reaction is observed. Courtesy Tri-Tech, Inc., Southport, NC, www.tritechusa.com 11 Microcrystalline Tests A technique considerably more specific than color tests is the microcrystalline test. A drop of a chemical reagent is added to a small quantity of the drug on a microscopic slide. After a short time, a chemical reaction ensues, producing a crystalline precipitate. The size and shape of the crystals, examined under a compound microscope, reveal the identity of the drug. Crystal tests for cocaine and methamphetamine are illustrated in Figure 02–03. Figure 02; A photomicrograph of a cocaine crystal formed in platinum chloride (4003).. San Bernardino County Sheriff. Figure 03; A photomicrograph of a methamphetamine crystal formed in gold chloride (4003) San Bernardino ,County Sheriff. 12 Over the years, analysts have developed hundreds of crystal tests to characterize the most commonly abused drugs. These tests can be rapidly executed and often do not require the isolation of a drug from its diluents; however, because diluents can sometimes alter or modify the shape of the crystal, the examiner must develop experience in interpreting the results of the test. Most color and crystal tests are largely empirical that is, scientists do not fully understand why they produce the results they do. From the forensic chemist’s point of view, this is not important. When the tests are properly chosen and used in proper combination, they reveal characteristics that identify the substance as a certain drug to the exclusion of all others. Chromatography Chromatography is a means of separating and tentatively identifying the components of a mixture. It is particularly useful for analyzing drug specimens, which may be diluted with practically any material to increase the quantity of the product available to prospective customers. The task of identifying an illicit-drug preparation would be arduous without the aid of chromatographic methods to first separate the mixture into its components. Thin-Layer Chromatography Thin-layer chromatography (TLC) uses a solid stationary phase and a moving liquid phase to separate the constituents of a mixture. Thin-layer chromatography is a powerful tool for solving many of the analytical problems presented to the forensic scientist. The method is both rapid and sensitive; moreover, less than 100 micrograms of suspect material is required for the analysis. In addition, the equipment necessary for TLC work has minimal cost and space requirements. Importantly, numerous samples can be analyzed simultaneously on one thin-layer plate. This technique is principally used to detect and identify components in complex mixtures. In TLC, the components of a suspect mixture are separated as they travel up a glass or plastic plate, eventually appearing as a series of dark or colored spots on the plate. This action is then compared to a standard sample separation of a specific drug, such as heroin. If both the standard and the suspect substances travel the same distance up the plate, they can tentatively be identified as being the same substance. 13 A thin-layer plate is prepared by coating a glass plate or plastic backing with a thin film of a granular material, usually silica gel or aluminum oxide. This granular material serves as the solid stationary phase and is usually held in place on the plate with a binding agent such as plaster of paris. If the sample to be analyzed is a solid, it must first be dissolved in a suitable solvent, then a few microliters of the solution is spotted with a capillary tube onto the granular surface near the lower edge of the plate. A liquid sample may be applied directly to the plate in the same manner. The plate is then placed upright in a closed chamber that contains a selected liquid, but the liquid must not touch the sample spot. The liquid slowly rises up the plate by capillary action. This rising liquid is the moving phase in Thin layer chromatography. As the liquid moves past the sample spot, the components of the sample become distributed between the stationary solid phase and the moving liquid phase. The components with the greatest affinity for the moving phase travel up the plate faster than those that have greater affinity for the stationary phase. When the liquid front has moved a sufficient distance (usually 10 centimeters), the development is complete, and the plate is removed from the chamber and dried . An example of the chromatographic separation of ink is shown in . Often the plate is sprayed with a chemical reagent that reacts with the separated substances and causes them to form colored spots. Figure 04 shows the chromatogram of a marijuana extract that has been separated into its components by TLC and visualized by having been sprayed with a chemical reagent. Figure 05 shows a sample suspected of containing heroin and quinine that has been chromatographed alongside known heroin and quinine standards. The distance the unknown material migrated up the suspect plate is compared to the distances that heroin and quinine migrated up a standard sample plate. If the distances are the same, a tentative identification can be made. However, such an identification cannot be considered definitive because numerous other substances can migrate the same distance up the plate when chromatographed under similar conditions. Thus, thin-layer chromatography alone cannot provide an absolute identification; it must be used in conjunction with other testing procedures to prove absolute identity. 14 Between a stationary liquid phase and a moving gas phase. In gas chromatography, the moving phase is called the carrier gas, which flows through acolumn constructed of glass. The stationary phase is a thin film of liquid within the column, which is known as a capillary column.. Figure 04; In thin-layer chromatography, (a) liquid sample is spotted onto the granular surface of a gel-coated plate. (b) The plate is placed into a closed chamber that contains a liquid. As the liquid rises up the plate, the components of the sample distribute themselves between the coating and the moving liquid. The mixture is separated, with substances with a greater affinity for the moving liquid traveling up the plate at a faster speed.. 15 Figure 05 ;(a) In thin-layer chromatography, the liquid phase begins to move up the stationary phase. (b) Liquid moves past the ink spot carrying the ink components up the stationary phase. (c) The moving liquid has separated the ink into its several components. Richard Megna\ Fundamental Photographs, NYC.. Figure 06; a thin layer standard Chromatogram of a marijuanaextract. Courtesy Sirchie Fingerprint Laboratories, Youngsville, NC,www.sirchie.com 16 Figure 07; Chromatographs of know heroin(1)and quinine (2) alongside a suspect sample (3).Richard saferstain. Capillary columns are composed of glass and are 15 to 60 meters in length. These types of columns are very narrow, ranging from 0.25 to 0.75 millimeter in diameter. Capillary columns can be made narrow because their stationary liquid phase is actually a very thin film coating the column’s inner wall. As the carrier gas flows through the capillary column, it carries with it. The components of a mixture that have been injected into the column. Components with a greater affinity for the moving gas phase travel through the column more quickly than those with a greater affinity for the stationary liquid phase. Eventually, after the mixture has traversed the length of the column, it emerges separated into its components. Closer analysis. 17 The Gas Chromatograph A simplified scheme of the gas chromatograph is shown in the figure. The operation of the instrument can be summed up briefly as follows: The carrier gas is fed into the column at a constant rate. The carrier gas, generally nitrogen or helium, is chemically inert. The sample under investigation is injected as a liquid into a heated injection port with a syringe, where it is immediately vaporized and swept into the column by the carrier gas. The column itself is heated in an oven in order to keep the sample in a vapor state as it travels through the column. In the column, the components of the sample travel in the direction of the carrier gas flow at speeds that are determined by their distribution between the stationary and moving phases. If the analyst has selected the proper liquid phase and has made the column long enough, the components of the sample will be completely separated as they emerge from the column. As each component emerges from the column, it enters a detector. One type of detector uses a flame to ionize the emerging chemical substance, thus generating an electrical signal. The signal is recorded on a strip-chart recorder as a function of time. This written record of the separation is called a chromatogram. A gas chromatogram is a plot of the recorder response (on the vertical axis) over time (on the horizontal axis). A typical chromatogram shows a series of peaks, each of which corresponds to one component of the mixture. under similar chromatographic conditions, gas chromatography cannot be considered an absolute means of identification. Conclusions derived from this technique must be confirmed with other testing procedures. Gas chromatography is widely used because of its ability to resolve a highly complex mixture into its components, usually within minutes. It hasthe added advantages of being extremely sensitive and yielding quantitative. results. Gas chromatography has sufficient sensitivity to detect and quantitate materials down to the nanogram (i.e., 0.000000001 gram). 18 Figure 08; Basic gas chromatography. Gas chromatography permits rapid separation of complex mixtures into individual compounds and allows identification and quantitative determination of each compound. As shown, a sample is introduced by a syringe (1) into a heated injection chamber (2). A constant stream of nitrogen gas (3) flows through the injector, carrying the sample into the column (4), which contains a thin film of liquid. The sample is separated in the column, and the carrier gas and separated components emerge from the column and enter the detector (5). Signals developed by the detector activate the recorder (7), which makes a permanent record of the separation by tracing a series of peaks on the chromatograph (8). The time it takes a component to emerge from the column identifies the component present, and the peak area identifies the concentration. Courtesy Varian Inc., Palo Alto, CA 19 Figure 09; An unknown mixture of barbiturates is identified by comparing its retention times to (b), a known mixture of barbiturates. Courtesy Varian Inc., Palo Alto, CA. Spectrophotometry The technique of chromatography is particularly suited for analyzing illicit drugs because it can separate a drug from other substances that may be present in the drug preparation. However, chromatography has the drawback of not being able to specifically identify the material under investigation. For this reason, other analytical tools are frequently used to identify drugs. 20 These include the technique of spectrophotometry, which can identify a substance by exposing it to a specific type of electromagnetic radiation. Theory of Light The knowledge of the nature and behavior of light is fundamental to understanding physical properties important to the examination of forensic evidence. One can think of light as a continuous wave. The wave concept depicts light as having the up-and-down motion of a continuous wav.. Such a wave can be characterized by two distinct properties: wavelength and frequency. The distance between two consecutive crests (high points) or troughs (low points) of a wave is called the wavelength; it is designated by the Greek letter lambda (l) and is typically measured in nanometers (nm), or millionths of a meter. The number of crests (or troughs) passing any one given point in a unit of time is defined as the frequency of the wave. Frequency is normally designated by the letter f and is expressed in cycles per second (cps). Frequency and wavelength are inversely proportional to one another, as shown by the relationship expressed in the following equation: In this equation, c represents the speed of light. Many of us have held a glass prism up toward the sunlight and watched it transform light into the colors of the rainbow. The process of separating light into its component colors is called dispersion. Visible light usually travels at a constant velocity of nearly 300 million meters per second. However, on passing through the glass of a prism, each color component of light is slowed to a speed slightly different from those of the others, causing each component to bend at a different angle as it emerges from the prism . This bending of light waves results in a change in velocity called refraction. The observation that a substance has a color is consistent with this description of white light. For example, when light passes through a red glass, the glass absorbs all the component colors of light except red, which passes through or is transmitted by the glass. Likewise, one can determine the color of an opaque object by observing its ability to absorb some of the component colors of light while reflecting others back to the eye. Color is thus a visual indication that objects absorb certain portions of visible light and transmit or reflect others. Scientists have long recognized this phenomenon and have learned to characterize chemical substances by the type and quantity of light they absorb. This has important implications for the identification and classification of forensic evidence.. 21 Figure 10; The frequency of the lower light wave is twice that of the upper wave. Electromagnetic Spectrum Visible light is only a small part of a large family of radiation waves known as the electromagnetic spectrum . All electromagnetic waves travel at the speed of light (c) and are distinguishable from one another only by their different wavelengths or frequencies. Hence, the only property that distinguishes X-rays from radio waves is the different frequencies the two types of waves possess.Similarly, the range of colors that make up the visible spectrum can be correlated with frequency. For instance, the lowest frequencies of visible light are red; waves with a lower frequency fall into the invisible infrared (IR) region.. The highest frequencies of visible light are violet; waves with a higher frequency extend into the invisible ultraviolet (UV) region. No definite boundaries exist between any colors or regions of the electromagnetic spectrum; instead, each region is composed of a continuous range of frequencies, each blending into the other. Just as a substance can absorb visible light to produce color, many of the invisible radiations of the electromagnetic spectrum are likewise absorbed. This absorption phenomenon is the basis for spectrophotometry, an analytical technique that measures the quantity of radiation that a particular material absorbs as a function of wavelength or frequency.. 22 Figure 11: The electromagnetic spectrum. The Spectrophotometer An object does not absorb all the visible light it is exposed to; instead, it selectively absorbs some frequencies and reflects or transmits others. Similarly, the absorption of other types of electromagnetic radiation by chemical substances is also selective. Selective absorption of a substance is measured by an instrument called a spectrophotometer, which produces a graph or absorption spectrum that depicts the absorption of light as a function of wavelength or frequency. The spectrophotometer measures and records the absorption spectrum of a chemical. The basic components of a simple spectrophotometer are the same regardless of whether it is designed to measure the absorption of UV, visible, or IR radiation. These components are illustrated diagrammatically, They include (1) a radiation source, (2) a mono chromator or Frequency selector, (3) a sample holder, (4) a detector to convert electromagnetic Radiation into an electrical signal, and (5) a recorder to produce a record of the signal. The measuring absorption of UV, visible, and IR radiation is particularly applicable to obtaining qualitative data pertaining to the identification of drugs. Ultraviolet and Visible Spectrophotometry Ultraviolet (UV) and visible spectrophotometry measure the absorption of UV and visible light as a function of wavelength or frequency. 23 For example, the UV absorption spectrum of heroin shows a maximum absorption band at a wavelength of 278 nanometers (see Figure 11–23). This shows that the simplicity of a UV spectrum facilitates its use as a tool for determining a material’s probable identity. For instance, a white powder may have a UV spectrum comparable to heroin and therefore may be tentatively identified as such. (Fortunately, sugar and starch, common diluents of heroin, do not absorb UV light.). This technique, however, does not provide a definitive result; other drugs or materials may have a UV absorption spectrum similar to that of heroin. Nevertheless, UV spectrophotometry is often useful in establishing the probable identity of a drug. For example, if an unknown substance yields a UV spectrum that resembles that of amphetamine), thousands of substances are immediately eliminated from consideration, and the analyst can begin to identify the material from a relatively small number of possibilities. A comprehensive collection of UV drug spectra provides an index that can rapidly be searched in order to tentatively identify a drug or, failing that, at least to exclude certain drugs from consideration. Figure 12 ;The ultraviolet spectrum of heroin. Figure 13; The ultraviolet spectrum of an amphetamine. 24 Infrared Spectrophotom etry In contrast to the simplicity of a UV spectrum, absorption in the infrared (IR) region provides a far more complex pattern. Figure 12–13 depicts the IR spectra of heroin and secobarbital. Here, the absorption bands are so numerous that each spectrum can provide enough characteristics to identify a substance specifically. Different materials always have distinctively different infrared spectra; each IR spectrum is therefore equivalent to a “fingerprint” of that substance and no other. This technique is one of the few tests available to the forensic scientist that can be considered specific in itself for identification. The IR spectra of thousands of organic compounds have been collected, indexed, and cataloged as invaluable references for identifying organic substances. The selective absorption of light by drugs in the UV and IR regions of the electromagnetic spectrum provides a valuable technique for characterizing drugs. Mass Spectrometry The Gas Chromatography section discussed the operation of the gas chromatograph. This instrument is one of the most important tools in a crime laboratory. Its ability to separate the components of a complex mixture is unsurpassed. However, gas chromatography has one important drawback: its inability to produce specific identification. A forensic chemist cannot unequivocally state the identity of a substance based solely on its retention time as determined by the gas chromatograph. Fortunately, by coupling the gas chromatograph to a mass spectrometer, forensic chemists have largely overcome this problem. A mixture’s components are first separated on the gas chromatograph. A direct connection between the gas chromatograph column and the mass spectrometer then allows each component to flow into the spectrometer as it emerges from the gas chromatograph. In the mass spectrometer, the material enters a high-vacuum chamber where a beam of high-energy electrons is aimed at the sample molecules. The electrons collide with the molecules, causing them to lose electrons and to acquire a positive charge. These positively charged molecules, or ions, are very unstable or are formed with excess energy and almost instantaneously decompose into numerous smaller fragments. 25 The fragments then pass through an electric or magnetic field, where they are separated according to their masses. The unique feature of mass spectrometry is that, under carefully controlled conditions, no two substances produce the same fragmentation pattern. In essence, one can think of this pattern as a “fingerprint” of the substance being examined (see Figure 14– 16).Mass spectrometry thus provides a specific means for identifying a chemical structure. It is also sensitive to minute concentrations. Mass spectrometry is widely used to identify drugs; however, further research is expected to yield significant applications for identifying other types of physical evidence. (Figure 14–16) illustrates the mass spectra of heroin and cocaine; here, each line represents a fragment of a different mass (actually the ratio of mass to charge), and the line height reflects the relative abundance of each fragment. Note how different the fragmentation patterns of heroin and cocaine are. Each mass spectrum is unique to each drug and therefore provides a specific test for identifying that substance. The combination of the gas chromatograph and mass spectrometer (GC/MS) is further enhanced when a computer is added to the system. The integrated gas chromatograph/mass spectrometer/computer system provides the ultimate in speed, accuracy, and sensitivity. With the ability to record and store in its memory several hundred Figure 14; How GC/MS works. Left to right, the sample is separated into its components by the gas chromatograph, and then the components are ionized and identified by characteristic fragmentation patterns of the spectra produced by the mass spectrometer. Courtesy Agilent Technologies, Inc., Palo Alto, CA. 26 Figure 15; The mass spectrum of heroin. (b) The mass spectrum of cocaine. mass spectra, such a system can detect and identify substances present in quantities of only one millionth of a gram. Furthermore, the computer can be programmed to compare an unknown spectrum against a comprehensive library of mass spectra stored in its memory. The advent of personal computers and micro circuitry has enabled the design of mass spectrometer systems that can fit on small tables. Such a unit is pictured in Figure 14–16, With data obtained from a GC/MS determination, a forensic analyst can, with one instrument, separate the components of a complex drug mixture and then unequivocally identify each substance present in the mixture. Research-grade mass spectrometers are found in laboratories as larger, floor-model . 27 Figure 16; A tabletop mass spectrometer. (1) The sample is injected into a heated inlet port, and carrier gas sweeps it into the column. (2) The GC column separates the mixture into its components. (3) In the ion source, a filament wire emits electrons that strike the sample molecules, causing them to fragment as they leave the GC column. (4) The quadrupole, consisting of four rods, separates the fragments according to their mass. (5) The detector counts the fragments passing though the quadrupole. The signal is small and must be amplified. (6) The data system is responsible for total control of the entire GC/MS system. It detects and measures the abundance of each fragment and displays the mass spectrum. Courtesy Agilent Technologies, Inc., Palo Alto, CA Conclusion: Drug testing, the technology of addiction medicine, identifies the use of specific drugs with the potential for misuse and addiction. Drug test results do not identify or diagnose substance use disorders, or establish the presence of impairment or physical dependence. Although drug testing is not a magic bullet that solves all of the problems associated with substance use disorders, drug testing is essential for the identification of recent drug use in all settings in which drug and in many cases, alcohol use is problematic. Drug tests are not the only way to identify drug use. It is also valuable to speak with people, since self-report identifies the use of drugs not included on test panels and covers a far longer period of time than do drug tests, and reports from others (e.g. family members, workplace supervisors, etc.) can provide useful information as well. 28 Self-report permits detailed questions related to the pattern of drug use, consequences arising from that use, and efforts that have been made to cut down or stop use. Thus, self-report is complementary to drug testing. It is wise to use both.The most basic and crucial questions about drug testing involve whom to test, what drugs to test for, what matrix to use (which body fluid or tissue to test), and what to do with the test results. These questions must be answered in each specific application of drug testing. Today drug testing is dramatically evolving to become more effective at the same time that the modern drug epidemic is evolving to become more complex. A generation ago, drug testing meant almost exclusively testing urine or blood. Now drug testing matrices includes oral fluid, hair, nails, sweat and breath. Similarly, in years past, drug testing meant the identification of the recent use of a relatively small number of widely-used, mostly agriculturally-produced, drugs. Now the dramatic and deadly increase in the misuse of prescription controlled substances presents a significant challenge to testing. While standard drug testing practice historically included testing for a small number of widely used drugs, such a narrow focus has become less useful today especially with the emergence of the ever-changing, synthetic “designer” drugs that are designed to evade detection through drug tests and to evade drug laws. Unlike drugs from earlier generations, today's drugs of abuse are often created in chemistry laboratories and not grown on farms; nor are neither they exclusively distributed through well-established criminal channels. Designer drugs, for example, are produced in clandestine laboratories all over the world and sold in convenience stores and gas stations or sent by global delivery services. In addition, prescription drugs associated with misuse and addiction usually originate with legal prescriptions written by physicians. Most drug testing panels today include less than 20 drugs, often as few as five. The available testing panels change much more slowly than the rapid changes in the patterns of drug use. The efforts to thwart drug testing are dramatically more sophisticated, better organized, and more available than was true even a decade ago. Looking forward, drug testing technology will become increasingly sensitive and easier to use, possibly leading to the development of breath testing for drugs of abuse, as is now done for alcohol. 29 The move to from urine testing to oral fluid testing reduces privacy concerns and minimizes the subversion problems that bedevil urine testing. Drug testing practices in the future must include identification of a far larger number of drugs. Drug testing must become less expensive and more resistant to subversion. Drug tests must rapidly identify newly emerging drugs of abuse. Important as these technical challenges are in drug testing, the challenge that is directly addressed by this White Paper, while different, is no less important. 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