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Two-dimensional gas chromatography (2D GC)–quadrupole time-of-flight mass spectrometry (QTOFMS) combined with derivatization was applied to determine naphthenic acids (NAs) in oil sand processed water (OSPW). Using the excellent resolution of 2D GC and mass resolution of QTOFMS with derivatization, 8 cyclohexane carboxylic acid isomers, 18 methylcyclohexyl carboxylic acid isomers, and 18 methylcyclohexyl acetic acid isomers were identified. Linear relationships across wide concentration ranges were established with correlation coefficients (R2) of 0.9995, 0.9992, and 0.9990, for cyclohexanecarboxylic acid, 4-methylcyclohexanecarboxylic acid, and 4-methylcyclohexane acetic acid. The precision, expressed as the relative standard deviation (RSD, n = 5), was from 7. 7–9.5% with recoveries between 72.0% and 84.9%. This method was applied to analyze sewage and showed high concentrations of naphthenic acids in untreated samples. [ABSTRACT FROM AUTHOR]

The Rosa chinensis cultivars Rosa Lvye, Rosa Knock out, Rosa Parade and Slater'scrimson China were analyzed for the volatile chemical composition in their flower petals. Headspace solid phase microextraction (HS-SPME) was applied to extract volatile flavors, and comprehensive two-dimensional gas chromatography (GC × GC) and quadrupole time-of-flight (QTOF) mass spectrometry (MS) were used for chemical profiling, including quantitative and qualitative analysis of the Rosa cultivars. A total of 97 volatile compounds were identified and 38 to 67 compounds were identified in each cultivar. The total concentrations of the extracted volatile compounds in the four cultivars were Rosa Knock out (750.21 ± 45.06 μg/g) > Rosa Parade (714.02 ± 6.94 μg/g) > Rosa Lvye (558.11 ± 9.08 μg/g) > Slater's crimson China (436.86 ± 3.21 μg/g). This study provides a specific chromatographic fingerprint for the Rosa chinensis cultivars, which can be applied in differentiation of the fragrance and aroma constituents. [ABSTRACT FROM AUTHOR]

The aroma fraction of fresh fruits is a key factor to evaluate quality and acceptance or resistance of customers. Due to the limited sensitivity of current analytical methods, many important aroma components are unidentified in most studies of fresh fruit. In this work, the aroma compounds in the fresh navel orange were studied by multidimensional gas chromatography quadrupole time-of-flight mass spectrometry which can simultaneously achieve one-dimensional and comprehensive two-dimensional separation on only one instrument, with no need to change columns. As a result, a total of 97 volatile compounds were determined by comprehensive two-dimensional gas chromatography while only 44 compounds were identified by one-dimensional gas chromatography. The identified compounds, which account for 98.30% of the volatile chemicals present in the orange, include 10 aldehydes, 8 ketones, 22 alcohols, 12 esters, 11 hydrocarbons and 34 terpenes. D-limonene was shown to be the predominant compound in fresh navel oranges. The results show that comprehensive two-dimensional gas chromatography provided reliable and comprehensive information on the aroma compounds in fresh navel oranges. [ABSTRACT FROM AUTHOR]

1.Aspirin (ASA) and clopidogrel (CLP) are used in combination as dual antiplatelet therapy (DAPT) for acute coronary syndrome based on their complementary mechanisms for platelet aggregation inhibition. However, the pharmacokinetics of such drug combination usage has not been thoroughly investigated. 2.In the current study, an LC-MS/MS method was developed to simultaneously determine the plasma concentrations of ASA and its metabolite salicylic acid (SA) with CLP and its metabolites, clopidogrel carboxylic acid (CLPM) and clopidogrel active metabolite derivative (CAMD). The pharmacokinetics of ASA, SA, CLP, CLPM and CAMD in rats receiving two-week DAPT with ASA and CLP were then determined. 3.After two-week DAPT with ASA and CLP in rats, the activities of aspirin esterase and rCyp2c11, enzymes mediating rat metabolism of ASA and CLP, respectively, in prepared rat liver microsomes were measured followed by further determination of rCyp2c11 mRNA expressions. The results demonstrated that DAPT led to minimal impact on aspirin esterase activity but significant decrease in rCyp2c11 activity and mRNA expression. 4.In conclusion, our findings on impairment in rCyp2C11 activity and mRNA expression by DAPT in rats could provide guidance on its safe clinical use with other CYP 2C19 substrates. [ABSTRACT FROM AUTHOR]