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A simple, rapid and low environmental toxicity ionic liquid-based ultrasonic-assisted dispersive liquid–liquid microextraction (DLLME) procedure was developed and validated for quantifying urinary levels of seven mercapturic acids (MAs) in human urine from nonsmokers and smokers. The ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate ([C8MIM][PF6]) and acetonitrile were used as extraction and disperser solvent, respectively, for the DLLME procedure, instead of using toxic chlorinated solvent. The factors affecting the extraction efficiency, such as the type and the amount of ionic liquid, type and volume of disperser solvent, extraction time and sample pH were optimized. In the proposed method, N-acetyl-S-(2-carboxyethyl)-l-cysteine (CEMA), N-acetyl-S-(3-hydroxypropyl)-l-cysteine (3-HPMA), N-acetyl-S-(2-hydroxy-3-butenyl)-l-cysteine + N-acetyl-S-(1-hydroxymethyl-2-propenyl)-l-cysteine (MHBMA isomers), N-acetyl-S-(phenyl)-l-cysteine (PMA), N-acetyl-S-(3,4-dihydroxybutyl)-l-cysteine (DHBMA), N-acetyl-S-(3-hydroxypropyl-1-methyl)-l-cysteine (HPMMA) and N-acetyl-S-(2-phenyl-2-hydroxyethyl)-l-cysteine + N-acetyl-S-(1-phenyl-2-hydroxyethyl)-l-cysteine (PHEMA isomers) can be determined. The optimized method showed a good precision level, with relative standard deviation values below 7.74 %. The method detection limits (MDL) between 0.05 and 2.50 µg L−1 and method quantification limits (MDQ) in the range of 0.20–8.25 µg L−1 were obtained for the proposed method. The recoveries for the analytes ranged from 85.32 to 127.61 %. Due to the good precision and the low limits of detection, the developed method is well suited for the determination of the analytes in human urine.

A heart-cutting two dimensional liquid chromatography coupled with tandem mass spectrometry method was developed for the analysis of tobacco-specific nitrosamines at low concentration level in Virginia-type cigarette smoke. A strong cation exchange column was utilized for the first dimensional separation, which effectively removed acidic and neutral components in the smoke, followed by a reversed phase liquid chromatography coupled with tandem mass spectrometric analysis. To capture components of the tobacco-specific nitrosamines in the effluent on the trapping column, a compensating pump was applied for on-line dilution and pH adjustment during the period of the tobacco-specific nitrosamines fraction transferring and enrichment. Highly sensitive determination of the tobacco-specific nitrosamines in mainstream cigarette smoke was achieved by isotope deuterated internal standards under the multiple reaction monitoring mode. Compared with traditional methodologies, the method was almost no matrix interference. Limits of quantity for the tobacco-specific nitrosamines were within 0.027–0.094 ng/mL. And the results showed good reproducibility and accuracy. Finally, the new method was applied to analysis of the Kentucky reference cigarettes and the results agreed well with joint experiments of Cooperation Centre for Scientific Research Relative to Tobacco. This article is protected by copyright. All rights reserved

In this study, a novel fully automated on-line coupled liquid chromatography-gas chromatography (LC-GC) technique was reported and applied for the determination of organochlorine pesticide residues (OCPs) in tobacco and tobacco products. Using a switching valve to isolate the capillary pre-column and the analytical column during the solvent evaporation period, the LC solvent can be completely removed and prevented from reaching the GC column and the detector. The established method was used to determinate the OCPs in tobacco samples. By using Florisil SPE column and employing GPC technique, polarity impurities and large molecule impurities were removed. A dynamic range 1-100ng/mL was achieved with detection limits from 1.5 to 3.3μg/kg. The method exhibited good repeatability and recoveries. This technology may provide an alternative way for trace analysis of complex samples.