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An efficient method for the simultaneous analysis of seven 2-hydroxy fatty acids (2-HFAs) as tert-butyldimethylsilyl (TBDMS) derivative was developed by gas chromatography-mass spectrometry in selected ion monitoring mode. New mass spectral data on 2-hydroxycapric, 2-hydroxypalmitic, 2-hydroxystearic and 2-hydroxybehenic acids as di-TBDMS derivatives for hydroxyl and carboxyl groups were built. Under the optimal conditions, the present method showed a good correlation coefficient ( r ≥ 0.999) in the range of 0.01-0.5 µg. The precision showed low relative standard deviation of <10%, and the accuracy (percentage relative error) varied from −5.2 to 0.3 for the seven 2-HFAs studied. Recovery rates of all 2-HFAs were ≥ 93.2% with good precision. When applied to normal human plasma, seven 2-HFAs were positively identified. Therefore, the present efficient method will be useful for simultaneous analysis of 2-HFAs in plasma. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT A novel derivatization method was developed for the simultaneous determination of six acidic metabolites of catecholamine and serotonin by gas chromatography-mass spectrometry (GC-MS). The metabolites were converted to O-ethoxycarbonyl/ tert-butyldimethylsilyl (EOC/TBDMS) derivatives for the direct GC-MS analysis in selected ion monitoring mode. Their mass spectral pattern as EOC/TBDMS derivatives showed characteristic fragment ions of [M - 15]+ and [M - 57]+, which permitted rapid and accurate structural confirmation of acidic metabolites. The present method was linear ( r ≥ 0.998), reproducible (percentage relative standard deviation = 1.0-10.0) and accurate (% relative error = −9.7-9.8) with detection limits of 0.001-4.7 ng/mL. When applied to human urine samples, the method allowed simultaneous determination of six acidic metabolites of catecholamine and serotonin. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT A selective and sensitive analytical method was developed for enantiomeric separation and determination of N-methyl-DL-aspartic acid (NMA). The method involved the conversion of each enantiomer into N-ethoxycarbonylated ( S)-(+)-2-octyl ester derivative for the direct separation by gas chromatography-mass spectrometry (GC-MS). The diastereomeric derivatives showed characteristic mass spectral properties for analysis by selected ion monitoring mode (SIM) and enabling enantioseparation on an achiral capillary column. Two enantiomers were baseline separated, and the detection limits for N-methyl-L-aspartic acid (NMLA) and N-methyl-D-aspartic acid (NMDA) were 0.07 and 0.03 ng/g, respectively. When applied to rat brain tissues for absolute configuration of NMA, only NMDA was determined, while NMLA was monitored as lower than the limit of detection. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Metabolic profiling analysis of free amino acids (AAs) in plasma (20 µL) was performed by gas chromatography-mass spectrometry in selected ion monitoring mode after ethoxycarbonyl/tert-butyldimethylsilyl derivatives. Characteristic fragment ions, including [M − 57] + ions, permitted sensitive and selective detection of most of the AAs in the presence of co-extracted carboxylic acids, including free fatty acids, at much higher levels. The overall method was linear ( r ≥ 0.9991), reproducible (relative standard deviation = 2.3-8.8%) and accurate (relative error = −7.3-7.7%) with detection limits of 0.01-1.9 ng/mL. A total of 18 AAs, 15 protein AAs and three nonprotein AAs were quantitatively screened in a normal human plasma sample. This selective and simple method using a minimal sample volume was effective for the quantitation of plasma free AAs. Copyright © 2007 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]