Determination of methamphetamine enantiomer ratios in urine by gas chromatography-mass spectrometry

[Research progress on chiral separation of amphetamines, ketamine, cathinones]

Enantiomers are ubiquitous in nature, and they are especially important in the field of pharmaceutical chemistry. Although the enantiomers of chiral drugs have identical chemical structures, they differ notably in their pharmacological, toxicological, pharmacokinetic, metabolic, and other biological activities. The same is true for amphetamines, ketamine, and cathinones, as the chiral separation of these three drugs is representative of drugs. Gas chromatography (GC), high performance liquid chromatography (HPLC), and capillary electrophoresis (CE) are widely used for the chiral separation of these three kinds of drugs. There are some similarities among the three methods for the chiral separation of amphetamines, ketamine, and cathinones: n-trifluoroacetyl-L-prolinyl chloride and (+)R-α-methoxy-α-trifluoromethylphenylacetic acid are the two typical chiral derivatization reagents used in GC. In HPLC, three kinds of chiral stationary phases are used: proteins, polysaccharides, and macrocyclic antibiotics. Cyclodextrin and its derivatives are most commonly used in CE. However, these three methods have inherent shortcomings. In the case of GC, impurities produced during chiral derivatization may interfere with the analysis, and high reaction temperatures affect the efficiency of chiral separation. HPLC has limited application scope and is expensive. In CE, there has no established process to determine the appropriate chiral selector. In recent years, research into application of the chiral separation of the above-mentioned three kinds of drugs has its own characteristics in forensic toxicology. The chiral separation of amphetamine drugs is mostly used to infer the prototype and synthesis route of drugs on the market. The chiral separation of ketamine involves a variety of biological samples. For cathinones, chiral separation methods emphasize their wide applicability. In this review, 66 reports published in professional local and overseas magazines during the past decade are collated. The characteristics of the enantiomers of amphetamines, ketamine, and cathinones as well as the mechanism of chiral recognition are briefly introduced. The commonness of the research and the application of chiral separation in forensic toxicology are reviewed. This paper proposes that the chiral separation of drugs can be further investigated from the following three aspects: 1) the use of computer technology to establish a molecular model for exploring the mechanism of chiral recognition; 2) developing new technologies for chiral separation and carrying out commercial research on the supercritical fluid method; 3) applying chiral separation to judicial practice, pharmaceutical research and development, and other practical fields.

Defunct brain stem cardiovascular regulation underlies cardiovascular collapse associated with methamphetamine intoxication

BACKGROUND

Intoxication from the psychostimulant methamphetamine (METH) because of cardiovascular collapse is a common cause of death within the abuse population. For obvious reasons, the heart has been taken as the primary target for this METH-induced toxicity. The demonstration that failure of brain stem cardiovascular regulation, rather than the heart, holds the key to cardiovascular collapse induced by the pesticide mevinphos implicates another potential underlying mechanism. The present study evaluated the hypothesis that METH effects acute cardiovascular depression by dampening the functional integrity of baroreflex via an action on brain stem nuclei that are associated with this homeostatic mechanism.

METHODS

The distribution of METH in brain and heart on intravenous administration in male Sprague-Dawley rats, and the resultant changes in arterial pressure (AP), heart rate (HR) and indices for baroreflex-mediated sympathetic vasomotor tone and cardiac responses were evaluated, alongside survival rate and time.

RESULTS

Intravenous administration of METH (12 or 24 mg/kg) resulted in a time-dependent and dose-dependent distribution of the psychostimulant in brain and heart. The distribution of METH to neural substrates associated with brain stem cardiovascular regulation was significantly larger than brain targets for its neurological and psychological effects; the concentration of METH in cardiac tissues was the lowest among all tissues studied. In animals that succumbed to METH, the baroreflex-mediated sympathetic vasomotor tone and cardiac response were defunct, concomitant with cessation of AP and HR. On the other hand, although depressed, those two indices in animals that survived were maintained, alongside sustainable AP and HR. Linear regression analysis further revealed that the degree of dampening of brain stem cardiovascular regulation was positively and significantly correlated with the concentration of METH in key neural substrate involved in this homeostatic mechanism.

CONCLUSIONS

We conclude that on intravenous administration, METH exhibits a preferential distribution to brain stem nuclei that are associated with cardiovascular regulation. We further found that the concentration of METH in those brain stem sites dictates the extent that baroreflex-mediated sympathetic vasomotor tone and cardiac responses are compromised, which in turn determines survival or fatality because of cardiovascular collapse.

Bioenergetics failure and oxidative stress in brain stem mediates cardiovascular collapse associated with fatal methamphetamine intoxication

BACKGROUND

Whereas sudden death, most often associated with cardiovascular collapse, occurs in abusers of the psychostimulant methamphetamine (METH), the underlying mechanism is much less understood. The demonstration that successful resuscitation of an arrested heart depends on maintained functionality of the rostral ventrolateral medulla (RVLM), which is responsible for the maintenance of stable blood pressure, suggests that failure of brain stem cardiovascular regulation, rather than the heart, holds the key to cardiovascular collapse. We tested the hypothesis that cessation of brain stem cardiovascular regulation because of a loss of functionality in RVLM mediated by bioenergetics failure and oxidative stress underlies the cardiovascular collapse elicited by lethal doses of METH.

METHODOLOGY/PRINCIPAL FINDINGS

Survival rate, cardiovascular responses and biochemical or morphological changes in RVLM induced by intravenous administration of METH in Sprague-Dawley rats were investigated. High doses of METH induced significant mortality within 20 min that paralleled concomitant the collapse of arterial pressure or heart rate and loss of functionality in RVLM. There were concurrent increases in the concentration of METH in serum and ventrolateral medulla, along with tissue anoxia, cessation of microvascular perfusion and necrotic cell death in RVLM. Furthermore, mitochondrial respiratory chain enzyme activity or electron transport capacity and ATP production in RVLM were reduced, and mitochondria-derived superoxide anion level was augmented. All those detrimental physiological and biochemical events were reversed on microinjection into RVLM of a mobile electron carrier in the mitochondrial respiratory chain, coenzyme Q10; a mitochondria-targeted antioxidant and superoxide anion scavenger, Mito-TEMPO; or an oxidative stress-induced necrotic cell death inhibitor, IM-54.

CONCLUSION

We conclude that sustained anoxia and cessation of local blood flow that leads to bioenergetics failure and oxidative stress because of mitochondrial dysfunction, leading to acute necrotic cell death in RVLM underpins cardiovascular collapse elicited by lethal doses of METH.

History of mass spectrometry at the Olympic Games

Mass spectrometry has played a decisive role in doping analysis and doping control in human sport for almost 40 years. The standard of qualitative and quantitative determinations in body fluids has always attracted maximum attention from scientists. With its unique sensitivity and selectivity properties, mass spectrometry provides state-of-the-art technology in analytical chemistry. Both anti-doping organizations and the athletes concerned expect the utmost endeavours to prevent false-positive and false-negative results of the analytical evidence. The Olympic Games play an important role in international sport today and are milestones for technical development in doping analysis. This review of the part played by mass spectrometry in doping control from Munich 1972 to Beijing 2008 Olympics gives an overview of how doping analysis has developed and where we are today. In recognizing the achievements made towards effective doping control, it is of the utmost importance to applaud the joint endeavours of the World Anti-Doping Agency, the International Olympic Committee, the international federations and national anti-doping agencies to combat doping. Advances against the misuse of prohibited substances and methods, which are performance-enhancing, dangerous to health and violate the spirit of sport, can be achieved only if all the stakeholders work together.

Interpretation of oral fluid tests for drugs of abuse

Oral fluid testing for drugs of abuse offers significant advantages over urine as a test matrix. Collection can be performed under direct observation with reduced risk of adulteration and substitution. Drugs generally appear in oral fluid by passive diffusion from blood, but also may be deposited in the oral cavity during oral, smoked, and intranasal administration. Drug metabolites also can be detected in oral fluid. Unlike urine testing, there may be a close correspondence between drug and metabolite concentrations in oral fluid and in blood. Interpretation of oral fluid results for drugs of abuse should be an iterative process whereby one considers the test results in the context of program requirements and a broad scientific knowledge of the many factors involved in determining test outcome. This review delineates many of the chemical and metabolic processes involved in the disposition of drugs and metabolites in oral fluid that are important to the appropriate interpretation of oral fluid tests. Chemical, metabolic, kinetic, and analytic parameters are summarized for selected drugs of abuse, and general guidelines are offered for understanding the significance of oral fluid tests.

Determination of tuaminoheptane in doping control urine samples

Since January 2007, the list of prohibited substances established by the World Anti-Doping Agency includes the sympathomimetic compound tuaminoheptane (1-methyl-hexylamine, 2-heptylamine). Primarily used as nasal decongestant drug it has been considered relevant for sports drug testing due to its stimulating properties. A confirmatory gas chromatographic-mass spectrometric procedure was developed including liquid-liquid extraction and imine formation of tuaminoheptane employing various aldehydes and ketones such as formaldehyde, acetaldehyde, benzaldehyde and acetone. Extraction and derivatisation conditions were optimised for utmost efficiency, and characteristic fragment ions obtained after electron ionisation allowed for a sensitive and selective analytical assay, which was validated with regard to recovery (50%), lower limit of detection (20 ng mL(-1)) as well as interday- and intraday precision (<15%). The applicability to authentic urine samples was demonstrated using administration study specimens obtained from two male persons using Rhinofluimucil (tuaminoheptane hemisulfate) for intranasal application. The administered drug was detected up to 46 h after repeated topical instillation of a total of approximately 3 mg.

Simultaneous determination of amphetamine and methamphetamine enantiomers in urine by simultaneous liquid–liquid extraction and diastereomeric derivatization followed by gas chromatographic–isotope dilution mass spectrometry

A simple, rapid, reliable, and economic analytical scheme starting with in situ liquid-liquid extraction and asymmetric (or diastereomeric) chemical derivatization (ChD) followed by gas chromatography (GC)-isotope dilution mass spectrometry (MS) is described for the simultaneous determination of D- and L-amphetamine (AP) and methamphetamine (MA) in urine which could have resulted from the administration of various forms of questioned amphetamines or amphetamines-generating drugs. By using L-N-trifluoroacetyl-1-prolyl chloride (L-TPC) as chiral derivatizing agent, resolutions of 2.2 and 2.0 were achieved for the separation of AP and MA enantiomeric pairs, respectively, on an ordinary HP-5MS capillary column. The GC-MS quantitation was carried out in the selected ion monitoring (SIM) mode using m/z 237 and 251 as the quantifier ions for the respective diastereomeric pairs of AP-L-TPC and MA-L-TPC. The calibration curves plotted for the two pairs of analytes stretch with good linearity down to 45 ng/mL, and the limits of detection and quantitation determined were as low as 40 and 45 ng/mL, respectively. Also, a comparative study using 10 real-case urine specimens previously screened as positive for MA administration showed mostly tolerable biases between the two sums (of concentration) of D- and L-MA obtained via an asymmetric L-TPC-ChD approach and via an ordinary pentafluoropropionylation (PFPA-ChD) approach, respectively, as well as between the two sums of D- and L-AP obtained thereupon, thus validating the proposed analytical scheme as a promising forensic protocol for the detailed analysis of enantiomeric amphetamines in urine.

Drug Testing in Blood: Validated Negative-Ion Chemical Ionization Gas Chromatographic–Mass Spectrometric Assay for Determination of Amphetamine and Methamphetamine Enantiomers and Its Application to Toxicology Cases

Background: Enantioselective analysis of amphetamine (AM) or methamphetamine (MA) in urine is already a well-established tool for differentiation of illicit from therapeutic ingestion of AM or MA derivatives. However, because of the increasing importance of plasma or serum in analytical toxicology, a method for enantioselective analysis of AM and MA in these matrices is needed.

Methods: AM and/or MA were extracted from 0.2 mL of blood plasma or serum by mixed-mode solid-phase extraction. After derivatization with S-(−)-heptafluorobutyrylprolyl chloride, the resulting diastereomers were separated by gas chromatography on a HP-5MS column during a 15-min program and detected by mass spectrometry in the negative-ion chemical ionization mode (NICI-GC-MS). The method was fully validated and applied to &gt;50 samples from authentic toxicology cases.

Results: The derivatized AM and MA enantiomers were well separated and sensitively detected. The method was linear from 5 to 250 μg/L per enantiomer with analytical recoveries, accuracy, and within- and between-run precision well within required limits. Extraction yields were 88.9–98.6%. Implications of concentrations and enantiomeric composition of AM and MA in the authentic samples were considered.

Conclusions: This sensitive, reliable, rapid NICI-GC-MS assay is suitable for enantioselective determination of AM and MA in blood plasma or serum samples.

Introduction to the application of capillary gas chromatography of performance-enhancing drugs in doping control

Performance-enhancing drugs banned by antidoping rules are detected in doping control preferably by hyphenated chromatographic techniques, capillary gas chromatography in particular. Based on the prohibited classes of substances and on the general aspects of sample collection and preparation, a survey is given about the usual procedures of screening, identification and confirmation of the most important doping agents: stimulants, narcotics, anabolics, diuretics, beta-blockers. In addition to gas chromatography itself, the application of various MS techniques doping is outlined.

Chiral gas chromatographic assay with flame ionization detection for amphetamine enantiomers in microsomal incubates

A chiral assay for amphetamine enantiomers in rat liver microsomal incubates is based on derivatization with (S)-(-)-N-(trifluoroacetyl)-prolyl chloride (S-TFPC), capillary chromatographic separation of the diastereomeric amide derivatives, and detection by a flame ionization detector. The method is capable of detecting low levels of S- or R-amphetamine. The assay is linear from 5 to 250 micrograms/mL for each enantiomer, and the limit of detection is 0.5 microgram/mL. The analytical method affords the average recoveries of 77.53 +/- 5.22% for R-amphetamine and 74.47 +/- 3.08% for S-amphetamine. The method allows the study of the metabolic depletion of S- and R-amphetamine in rat liver microsomal incubates. The time-dependent concentration of amphetamine enantiomers in rat liver microsomes was determined, and the stereoselectivity of amphetamine phase I metabolism was observed.

Methamphetamine--properties and analytical methods of enantiomer determination

Methamphetamine is one of the most frequently abused drugs of today. Due to its stereogenic center, it can exist as single enantiomer. Like many other chiral compounds, methamamphetamine enantiomers exhibit different pharmacological effects on living organisms. For this reason, it is necessary to develop enantioselective and sufficiently sensitive methods of determination. This review focuses on methamphetamine with an accent on analytical chemistry and especially on chiral separations of this toxicologically important compound.

Determination of drugs of abuse in blood

The detection and quantitation of drugs of abuse in blood is of growing interest in forensic and clinical toxicology. With the development of highly sensitive chromatographic methods, such as high-performance liquid chromatography (HPLC) with sensitive detectors and gas chromatography-mass spectrometry (GC-MS), more and more substances can be determined in blood. This review includes methods for the determination of the most commonly occurring illicit drugs and their metabolites, which are important for the assessment of drug abuse: Methamphetamine, amphetamine, 3,4-methylenedioxymethamphetamine (MDMA), N-ethyl-3,4-methylenedioxyamphetamine (MDEA), 3,4-methylenedioxy-amphetamine (MDA), cannabinoids (delta-9-tetrahydrocannabinol, 11-hydroxy-delta-9-tetrahydrocannabinol, 11-nor-9-carboxy-delta-9-tetrahydrocannabinol), cocaine, benzoylecgonine, ecgonine methyl ester, cocaethylene and the opiates (heroin, 6-monoacetylmorphine, morphine, codeine and dihydrocodeine). A number of drugs/drug metabolites that are structurally close to these substances are included in the tables. Basic information about the biosample assayed, work-up, GC column or LC column and mobile phase, detection mode, reference data and validation data of each procedure is summarized in the tables. Examples of typical applications are presented.

Derivatization procedures for gas chromatographic-mass spectrometric determination of xenobiotics in biological samples, with special attention to drugs of abuse and doping agents

The development of low cost MS detectors in recent years has promoted an important increase in the applicability of GC-MS system to analyze for the presence of foreign substances in the human body. Drugs and toxic agents are in vivo metabolized in such a way that more polar compounds are usually formed. Derivatization of these metabolites is often an unavoidable requirement for gas chromatographic analysis. Application of derivatization methods in recent years has been relevant, especially for silylation, acylation, alkylation and the formation of cyclic or diastereomeric derivatives. Given the relevance of drug of abuse testing in modern toxicology, main derivatization procedures for opiates, cocaine, cannabis, amphetamines, benzodiazepines and LSD have been reviewed. Papers describing the analyses of drugs of abuse in matrixes other than blood, such as hair or sweat, have received special attention. Advances in derivatization for sports drug testing have been particularly relevant for anabolic steroids, diuretics and corticosteroids. Among the several methodologies applied, the formation of trimethylsilyl, perfluoroacyl or methylated derivatives have proved to be both versatile and extensively used. Further advances in derivatization for GC-MS applications in clinical and forensic toxicology will depend on the one hand on the degree of further use of GC-MS for routine applications and, on the other hand, on the alternative progress made for developments in LC-MS or CE-MS. Last but not least, the appearance of comprehensive libraries in which reference spectra for different derivatives of many drugs and their metabolites are collected will have an important impact on the expansion of derivatization in GC-MS for toxicological applications.

Determination of amphetamine, methamphetamine and amphetamine-derived designer drugs or medicaments in blood and urine

This paper reviews procedures for the determination of amphetamine, methamphetamine and amphetamine-derived designer drugs or medicaments in blood and urine. Papers published from 1991 to early 1997 were taken into consideration. Gas chromatographic and liquid chromatographic procedures with different detectors (e.g., mass spectrometer or diode array) were considered as well as the seldom used thin-layer chromatography and capillary electrophoresis. Enantioselective procedures are also discussed. A chapter deals with amphetamine-derived medicaments, e.g. anoretics, antiparkinsonians or vasodilators, which are metabolized to amphetamine or methamphetamine. Differentiation of an intake of such medicaments from amphetamine or methamphetamine intake is discussed. Basic information about the biosample assayed, internal standard, work-up, GC column or LC column and mobile phase, detection mode, reference data and validation data of each procedure is summarized in Tables. Examples of typical applications are presented.

Enantioselective gas chromatographic assay of 2-alkylamines using N-(trifluoroacetyl)prolyl derivatives and a chiral capillary column

The chromatographic properties of (R)-(+)-N-(trifluoroacetyl)prolyl and (S)-(-)-N-(trifluoroacetyl)prolyl derivatives on a chiral gas chromatography capillary column were assessed for the measurement of enantiomeric purities of 2-butylamine, 2-pentylamine, 2-hexylamine, 2-heptylamine and 2-octylamine and their N-methyl analogues, which are used as precursors in the synthesis of some selective, specific, irreversible monoamine oxidase-B inhibitors. Using a Chirasil-Val column it was possible to separate all four diastereomers of the primary amines, and three of the four isomers of the secondary amines. Quantitation of the enantiomers is facilitated even with enantiomerically impure reagent when compared to the use of an achiral phase.

Methamphetamine psychosis: spontaneous recurrence of paranoid-hallucinatory states and monoamine neurotransmitter function

We studied the process that triggers spontaneous recurrences of methamphetamine (MAP) psychosis, a phenomenon known as flashbacks, in 28 female patients who experienced flashbacks, by comparing them with 92 female nonflashbackers with a history of previous MAP psychosis. The study evaluated plasma monoamine neurotransmitter function in 12 of the 28 flashbackers and in 8 of the 92 nonflashbackers. Control data were obtained from 28 normal, healthy females composed of 13 MAP users and 15 nonusers, none of whom became psychotic. The 28 flashbackers had experienced significantly greater frequencies of threatening events and frightening paranoid-hallucinatory states during previous MAP abuse than the 92 nonflashbackers. The dominant triggering factor was a mild fear of other persons. Plasma norepinephrine (NE) levels were significantly higher in the 12 flashbackers during flashbacks than during periods of normalcy and were significantly higher than those in the 13 user and 15 nonuser control subjects. Plasma NE levels in the 12 flashbackers during periods of normalcy were significantly higher than those in the 13 user control subjects. The eight nonflashbackers had significantly higher NE levels than the 13 user control subjects. This suggests that an increase in peripheral noradrenergic activity may be related to the occurrence of flashbacks. The present study suggests that repeated MAP use with frightening experiences may induce sensitivity to psychosocial stressors. A mild fear of other persons may have actualized the encoded frightening memories associated with the frightening experiences via increased sensitivity to psychosocial stressors. Thus, flashbacks may have been caused through an increase in peripheral noradrenergic activity.

Monoamine neurotransmitter metabolites and spontaneous recurrence of methamphetamine psychosis

The present study was conducted to evaluate plasma levels of monoamine neurotransmitter metabolites in spontaneous recurrences of methamphetamine psychosis (i.e., flashbacks). The subjects were 50 physically healthy females comprised of 25 who experienced flashbacks (flashbackers), 18 who did not experienced methamphetamine psychosis, and 9 who were currently suffering from persistent methamphetamine psychosis. The control data were available from 28 normal healthy females, of whom 20 had previously abused methamphetamine (users) and 8 who had not (nonusers), none of whom had ever become psychotic. Plasma levels of norepinephrine (NE), dopamine (DA), and 5-hydroxytryptamine (5-HT), and their respective metabolites were assayed. Plasma NE levels were significantly higher in the 25 flashbackers during their flashbacks than during their periods of normalcy, and were significantly higher than those in the 20 user and 8 nonuser controls. Plasma 3-methoxy-4-hydroxyphenylglycol (MHPG) levels during flashbacks were significantly higher than those in the 20 user controls. The nine subjects with persistent methamphetamine psychosis had significantly higher NE levels than the user and nonuser controls. The 16 nonflashbackers had significantly higher MHPG levels than the user controls. The present study suggests that an increase in peripheral noradrenergic activity is related to the occurrence of flashbacks.

Stimulants, narcotics and beta-blockers: 25 years of development in analytical techniques for doping control

More than 25 years of developing doping control methods have led to comprehensive screening and confirmation procedures for stimulants, narcotics and beta-blockers. Much of this work has been initiated and/or improved by the late Prof. Dr. Manfred Donike. The methodological approach covered in this overview was applied to doping control procedures during the XXV Summer Olympics in Barcelona, Spain, in 1992 and the XVII Winter Olympics in Lillehammer, Norway, in 1994. Urine samples are screened through a combination of two analytical methods that are complementary: (a) gas chromatographic analysis of the parent compound and unconjugated metabolites, following single-step sample extraction and detection by a nitrogen-specific detector based on a retention index identification system and (b) gas chromatographic analysis including also conjugated drugs and metabolites after hydrolysis, solid-phase extraction, derivatisation and mass spectrometric detection. Confirmation and identification is always performed by gas chromatographic separation and full scan mass spectrometric detection. These methods facilitate the rapid screening and confirmation of more than 100 stimulants, narcotic analgesics and beta-blockers in urine for at least 24 h after the intake of a pharmaceutical dose. Application of the methods ensures high quality standards for the unequivocal identification of doping agents as well as a rapid turnaround time for sample analyses.

Chiral identification and determination of ephedrine, pseudoephedrine, methamphetamine and methcathinone by gas chromatography and nuclear magnetic resonance

The enantiomers of the related substances methamphetamine, ephedrine, pseudoephedrine and methcathinone were determined by both gas chromatography after derivatization and by nuclear magnetic resonance using a chiral solvating agent. For GC the substances were derivatized with (R)-(+)-alpha-methoxy-alpha-(trifluoromethyl)phenylacetic acid (MTPA) to give diasteromeric derivatives. Resolution (baseline) of at least 1.6 was obtained between all derivatives. NMR determination of the enantiomers was conducted in a chiral environment by the addition of the chiral solvating agent, (R)-(+)-1,1'-bi-2-naphthol, to NMR solutions of the substances. Racemization of methcathinone was demonstrated to be facile by exposure to alkaline solutions for varying periods of time. Enantiomeric ratios of some products derived from the oxidation of ephedrine were determined.

Sensitive enantiomer-specific high-performance liquid chromatographic analysis of methamphetamine and amphetamine from serum using precolumn fluorescent derivatization

In order to study the stereoselective disposition of methamphetamine (MAP), a widely abused drug, we have developed a sensitive HPLC assay to separate and quantitate the enantiomers of MAP and amphetamine (AP) in rat serum. Serum samples to which was added aniline sulfate (internal standard) were alkalized with 0.02 M carbonate buffer (pH 10.6) and extracted with ethyl acetate. Following back extraction with hydrochloric acid, neutralization, and reconstitution, the sample was derivatized with (-)-fluorenylethyl chloroformate overnight at room temperature. The derivatized products were separated following injection onto a reversed-phase C18 column. The mobile phase consisted of 0.02 M acetate buffer-acetonitrile-tetrahydrofuran (46:39:15, v/v). The fluorescent intensity of the effluent was monitored at excitation and emission wavelengths of 265 and 330 nm, respectively. The derivatized aniline, R-, S-AP, R- and S-MAP had retention times of 21.0, 22.6, 23.6, 27.7 and 29.0 min, respectively. Linear standard curves were obtained over the concentration range of 5-250 ng/ml. The inter-day and intra-day coefficients of variation for the assay of all four compounds at 12.5, 50.0 and 250 ng/ml were in the range of 2.1-18.6%. The method was applied to quantitate the concentrations of MAP and AP enantiomers in rat serum following a short term intravenous infusion of racemic MAP (15 mg/kg). There were no differences in serum concentrations of MAP enantiomers but the concentrations of S-AP were consistently greater than those of R-AP. These data suggest a stereoselective disposition for the formation and/or elimination of amphetamine.