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

(+) or (-)-1-(9-fluorenyl)ethyl chloroformate as chiral derivatizing agent: A review

Over the last 30years, (±)-1-(9-fluorenyl)ethyl chloroformate ((±)-FLEC) was used as a chiral derivatizing agent in various analytical applications involving a wide range of endogenous, pharmaceutical and environmentally relevant molecules. This comprehensive review aims to present all the significant aspects related to the state of the art in FLEC labeling and subsequent chiral separation of the resulting diastereomers using LC, SFC and CE techniques.

Monitoring precursor chemicals of methamphetamine through enantiomer profiling

Smuggling of methamphetamine is affected by enforced regulation and international situation, resulting in changes of precursors and synthetic methods used. Enantiomer ratio of methamphetamine can provide information concerning its precursor and synthetic method. This information is useful for the prevention of smuggling methamphetamine and its precursor, and resultant reduction of methamphetamine abuse. In the present study, we investigated on the enantiomer ratios of 433 crystalline methamphetamine samples seized in Korea from 1994 to 2005. Excluding 17 samples of low purity, 416 samples were used for enantiomer profiling. The methamphetamine samples were derivatized with (S)-(+)-alpha-methoxy-alpha-(trifluoromethyl)phenylacetyl chloride ((S)-(+)-MTPACl), and the derivatives were analyzed by GCMS in selected ion monitoring (SIM) mode. The enantiomer ratios of the samples were calculated from the standard calibration curves of each enantiomer, both of which showed good linearity in the range of 0-1.2 microg. Most of the seizures were pure S(+)-enantiomer, but 21% (95 of 416 samples) contained R(-)-enantiomer above 1%. They began to appear from 1997, and increased continuously up to 50% in the year 2005 (55 of 111 samples). From this study, we could find out that alternative precursors have been used recently for the illicit manufacture of methamphetamine seized in Korea.

Determination of amphetamines in human urine by liquid chromatography with fluorimetric detection using a solid-phase extraction procedure

A precise and feasible HPLC method has been developed for the analysis of amphetamine (AMPH), methamphetamine (MAMPH) and methylenedioxymethamphetamine (MDMA, ecstasy) in human urine. A chromatographic run on a C8 Genesis (150 mm x 4.6 mm, 5 microm) column maintained at 30 degrees C lasts about 17 min, using a mobile phase composed of ACN (12%) and a pH 2.5 phosphate buffer (88%) containing 0.3% triethylamine. Mirtazapine was used as the internal standard. Good linearity was found in the 100-2000 ng/mL concentration range for AMPH and MAMPH and in the 12-2000 ng/mL concentration range for MDMA. The pretreatment of urine samples was carried out by means of a careful SPE procedure on C2 cartridges. The extraction yields were very satisfactory for all analytes, with average values greater than 97%. The leading conditions allowed the determination of AMPH, MAMPH and MDMA with satisfactory precision and accuracy. The method has been successfully applied to the determination of the analytes in urine of AMPH users.

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 >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.

Preparation of immunoaffinity columns for direct enantiomeric separation of amphetamine and/or methamphetamine

Immunoaffinity chromatographic columns were prepared for direct enantiomeric determination of racemic methamphetamine and amphetamine in this study. The stationary phase was synthesized by covalently bonding an anti-D-methamphetamine monoclonal antibody onto a pre-activated support (e.g. silica, sepharose 4B). Chromatographic results revealed that the immunoaffinity columns achieved enantiomeric separation of racemic amphetamine and methamphetamine. The immunoaffinity columns also have the ability to directly extract D-methamphetamine from urine by changing the pH of the mobile phase, this ability making it practical for the columns to determine a very low concentration of D-methamphetamine in urine.

Investigation of stereoselective metabolism of amphetamine in rat liver microsomes by microdialysis and liquid chromatography with precolumn chiral derivatization

The utility of microdialysis as a quantitative sampling technique for in vitro drug metabolism studies was demonstrated by investigating the stereoselective metabolism of D-, L- and DL-amphetamine by the cytochrome P-450 enzymes. Microdialysates containing the isomers of amphetamine and its metabolite were derivatized with the fluorescent chiral derivatizing agent, (-)-fluorenylethyl chloroformate. The diastereoisomers were isocratically separated by liquid chromatography (LC) on a reversed-phase C18, 3-micron (100 x 3.2 mm) column. The intra- and inter-assay relative standard deviation (R.S.D.) was below 10%. Michaelis-Menten parameters, K(m) and Vmax were obtained for the formation of both D- and L-hydroxyamphetamine from D-, L- and DL-amphetamine in the concentration range of 10-350 microM.

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 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.

Capillary electrophoresis-laser-induced fluorescence detection of amphetamine in the brain

Prefrontal cortex microdialysis was done in rats that had received intraperitoneal amphetamine (AMPH). Samples were derivatized with 10(-4) M fluorescein isothiocyanate and incubated for 18 h. AMPH was separated by capillary electrophoresis (CE) and detected by laser-induced fluorescence detection (LIFD) from 30 to 150 min after injection. The limit of mass detection was 3 amol, which is three orders of magnitude lower than that in gas chromatography-mass spectrometry, and the limit of concentration detection was 3 x 10(-9) M. The results showed that CE-LIFD is a good method for detecting AMPH in brain dialysates of rats.

Influence of activated charcoal on the disposition kinetics of methamphetamine enantiomers in the rat following intravenous dosing

Methamphetamine (MAP) is a central nervous system stimulant that is widely abused by populations of several countries. There is no specific antidote for the treatment of an overdose. Activated charcoal administered orally has been used to enhance the systemic elimination of certain toxic substances via "gastrointestinal dialysis". The results of in vitro studies have shown that MAP can be rapidly adsorbed from solution by activated charcoal. We have evaluated the effect of a single oral dose of activated charcoal on the disposition kinetics of MAP following a short iv infusion. Male Sprague-Dawley rats were given an oral dose of activated charcoal (Actidose-aqua, 1 g/kg) 10 min before a short iv infusion of racemic MAP; whereas the control group was given an equivalent volume of water. Enantiomers of MAP and metabolites in serum and urine were analyzed by an enantiomer-specific method which employed HPLC and detection of a fluorescent derivative. There were no differences in any of the disposition parameters between the two groups. Within each group, the clearance (CLs) of l-MAP was greater than that of d-MAP. However, there were no differences in the steady-state volume of distribution (Vss). The CLs (mL/(min kg)) and Vss (L/kg) values for l- and d-MAP in the control group were (mean +/- SD): 55.8 +/- 20.4, 48.7 +/- 17.9, 2.64 +/- 1.16, and 2.90 +/- 1.36, respectively. The corresponding values in the charcoal-pretreated group were (mean +/- SD): 57.4 +/- 23.4, 51.1 +/- 20.7, 2.79 +/- 1.32, and 2.98 +/- 1.47. These results suggest that oral activated charcoal does not enhance the elimination of MAP from the body.

Disposition of CS-670, a novel nonsteroidal anit-inflammatory drug, and its metabolites in healthy human volunteers

CS-670, a novel nonsteroidal anti-inflammatory drug, is a racemic prodrug. Plasma concentrations and urinary excretion of CS-670 and its metabolites were determined in experimental subjects after oral administration at a single 120 mg dose. CS-670 and four metabolites, the saturated ketone (M-A), unsaturated-alcohol (M-B), cis-alcohol (M-C), and trans-alcohol (M-D), were quantitated by GC-MS. The major metabolites in human plasma were M-B, M-C, and M-D and their terminal half-lives (t1/2) were 0.9, 2.6, and 1.2 h, respectively. The total recovery in the urine was 26% of the dose, but unchanged CS-670 accounted for less than 2% over a 48 h period. In addition, the absolute configurations of the metabolites were examined by HPLC after derivatization with chiral reagents. It was found that the configuration of the propionic acid moiety of the metabolites, M-B, M-C, and M-D, in human plasma, was rapidly inverted from (-)-(R) to the (+)-(S) configuration in stereoselective biotransformation. Furthermore, the configurations of the 1'- and 2'-carbons of M-C and M-D, were found to be (1'R, 2'S) and (1'R, 2'S), respectively. These results show that CS-670 is readily biotransformed by chiral inversion of the 2-arylpropionic acid moiety and stereoselective reduction of the alpha, beta-unsaturated ketone moiety in humans.