Efficient determination of amphetamine and methylamphetamine in human urine using electro-enhanced single-drop microextraction with in-drop derivatization and gas chromatography.

An efficient method for the determination of amphetamine (AM) and methylamphetamine (MA) using electro-enhanced single-drop microextraction (EE-SDME) and gas chromatography has been developed. One advantage of this method is that the extraction efficiency is greatly enhanced by the electric field acceleration of the mass transfer of target analytes from the sample solution to the organic solvent drop. In addition, the extracted analytes were in situ derivatized with isobutyl chloroformate (IBCF) in the droplet, which further improved the sensitivity of this method. Under the optimum conditions, the enrichment factors (EFs) for AM and MA were 247 and 782, respectively. The proposed method exhibited low limits of detection (0.27 µg/L for AM and 0.14 µg/L for MA) and good linearity over the concentration range between 1 and 2000 µg/L with regression coefficients (r2) of more than 0.99. The intra- and interday recoveries were from 89.6 to 96.2% and 82.7-90.5%, respectively, and the intra- and interday precisions (RSDs) were from 5.2 to 8.3% and 8.9-12.8%. The proposed method was applied to the determination of amphetamines in a urine sample.

[Determination of six amphetamine-type stimulants in urine samples using electro-enhanced single drop microextraction-gas chromatography].

A method for the simultaneous determination of six amphetamine-type stimulants (ATSs) in urine by electro-enhanced single drop microextraction-gas chromatography (EE-SDME-GC) with a flame ionization detector (FID) was developed. The influences of the EE-SDME parameters on the extraction efficiencies were investigated. The 5 mL-samples at pH 7 were extracted with 2 µL dichloromethane for 3 min under an applied potential of -2.5 V. The analysis was performed on a HP-5 capillary column (30 m×0.32 mm×0.25 µm) using a flame ionization detector. The six ATSs were linear in the range of 20-1000 µg/L with correlation coefficients (r) between 0.989 and 0.997. The limits of detection (S/N=3) of the six ATSs ranged from 3.2 to 7.6 µg/L. The recoveries of the six ATSs in the spiked urine samples were 91.6%-111.2%, and the relative standard deviations were 2.9%-6.2% (n=3) at three spiked levels of 50, 100 and 500 µg/L. This method was rapid, sensitive, reliable, easily-operated and environment-friendly for the determination of the ATSs in urine samples.

Oxidized multiwalled carbon nanotubes coated fibers for headspace solid-phase microextraction of amphetamine-type stimulants in human urine.

Carbon nanotubes (CNTs) have attracted a lot of attention as effective sorbents due to their strong sorption properties and several potential applications in many fields. In this work, the acid oxidized multiwalled carbon nanotubes (MWCNTs-COOH) was coated onto a stainless steel wire by a simple physical adhesion approach to develop solid-phase microextraction (SPME) fibers. By combination of the MWCNTs-COOH coated fiber-based headspace SPME and gas chromatography-mass spectrometry (GC-MS), the developed method demonstrates a good enhancement factor (288-651), low limits of detection (LODs, 0.2-1.3µg/L) for determination of amphetamine-type stimulant drugs (ATSs) in urine samples. The recoveries of the spiked ATSs (5, 50 and 500µg/L) were in the range of 88-107%, the calibration curve was linear for concentrations of analytes in the range from 0.5 to 1000µg/L (R=0.963-0.999). Furthermore, single fiber repeatability and fiber-to-fiber reproducibility were in the range of 2.3%-6.2% (n=6) and 5.7%-9.8% (n=3), respectively. The MWCNTs-COOH coated fiber is highly thermally stable and can be used over 150 times. The method was successfully applied to the forensic determination of amphetamine (AMP) and methamphetamine (MAMP) in human urine samples and satisfactory results were achieved.

Determination of 13 Organic Toxicants in Human Blood by Liquid-Liquid Extraction Coupling High-Performance Liquid Chromatography Tandem Mass Spectrometry.

Pesticides and antidepressants are frequently misused in drug-facilitated crime because of their toxicological effect and easy-availability. Therefore, it is essential for the development of a simple and reliable method for the determination of these organic toxicants in biological fluids. Here, we report on an applicable method by the combination of optimized liquid-liquid extraction (LLE) procedure and high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) to identify and quantify dimethoate, omethoate, dichlorvos, carbofuran, fenpropathrin, diazepam, estazolam, alprazolam, triazolamm, chlorpromazine, phenergan, barbitone and phenobarbital in human blood. The method demonstrated a linear calibration curve in range of 20 - 500 µg/L (r > 0.994). The accuracy evaluated by recovery spiked at three different concentrations (50, 100 and 200 µg/L) was in the range of 58.8 - 83.1% with a relative standard deviations (RSD) of 3.7 - 7.4%. The limits of quantification ranged over 6.7 - 33.3 µg/L. This method was proved to be simple and reliable, and was thus successfully applied to forensic toxicology.

Catalytic wet oxidation of aqueous methylamine: comparative study on the catalytic performance of platinum-ruthenium, platinum, and ruthenium catalysts supported on titania.

Promotion of the dispersion of Ru species supported on TiO2 was achieved by introduction of Pt component and the role of Pt in enhancing the catalytic performances of Pt-Ru was investigated with catalytic wet air oxidation of methylamine used as a probing reaction. It was found that Pt-Ru/TiO2 displayed a much better catalytic performance compared with Pt/TiO2 and Ru/TiO2 catalysts due to having the highest dispersion of active species. Both high total organic carbon conversion and nitrogen selectivity (∼100%) over Pt-Ru/TiO2 catalyst were achieved at low temperature (200 °C). X-ray photoelectron spectroscopy characterization indicated that there were strong interactions between metal particles and the support, which may increase the catalytic performance of catalysts.