Xiaolan Huang

Gas Chromatographic Retention Time Rule and Mass Spectrometric Fragmentation Rule of Fatty Acids and Its Application in Food

Abstract The fat in food samples was extracted using Soxhlet technique, and in-vial derivatized to their corresponding methyl ester and subsequently analyzed by GC/MS. Sufficient separation for the homologous and isomers of methyl esters of fatty acids was achieved with HP-88 capillary column. The gas chromatographic retention time rule of homologues and isomers of fatty acids methyl esters was studied, and mass spectrometric fragmentation rule was also investigated in this study. A novel method which can ascertain the carbon atom number and double bond number in fatty acids using 3 characteristic ions, as well as can confirm cis- and trans-isomers and double-bond positional isomers based on retention time rule, was established. Using this method, the contents of homologues and different kinds of isomers of fatty acids can be determined without standards. This method can be applied to the investigation of the compositions of fatty acids, especially trans-fatty acid, and determination fatty acids in lipid and food samples. The method is accurate, reliable, and convenient, and has been applied to the quantitative determination of the content of trans-fatty acid in food samples.

Determination of Polybromodiphenyl Ethers and Polybromobiphenyls in Electrical and Electronic Equipments by Gas Chromatography-Mass Spectrometry

Abstract A method for the determination of polybromobiphenyls (PBBs) and polybromodiphenyl ethers (PBDEs) in electrical and electronic equipments by GC-MS has been developed. The pretreatment procedures, such as solvent selection, extraction method, and column type, were discussed in detail, and standard mass spectral library of PBBs and PBDEs was established. The PBBs and PBDEs were identified by the combination of retention time, isotopic rule of bromine, characteristic ion, and retrieved reference library. The detection limit was as low as 5 mg kg−1, and the recovery rates of PBBs and PBDEs were 92.5% and 91.3%, respectively. The relative standard deviation (RSD) was lower than 4.3%. The most important characteristic of this method was its short separation time, which was within 6 min and it is the fastest that has ever been reported. Results that met the directions of Restriction of Hazardous Substances Directive (RoHS) were obtained. This method can be used to analyze the bromine-based flame retardant in electrical and electronic equipments, plastic, rubber, and decorative materials for automobiles.

SIMULTANEOUS DETERMINATION OF 17 TOXIC ALKALOIDS IN HUMAN FLUIDS BY LIQUID CHROMATOGRAPHY COUPLED WITH ELECTROSPRAY IONIZATION TANDEM MASS SPECTROMETRY

A sensitive and specific method was proposed and validated for the simultaneous determination of 17 poisonous alkaloids in human blood and gastric juice by liquid chromatography and electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). After mixing with boric acid buffer solution (pH 9), the samples were extracted with chloroform followed by chloroform-ether (2:1, v/v). The simultaneous qualitative and quantitative analysis of 17 alkaloids, including koumine, atropine, scopolamine, brucine, strychnine, aconitine, bulleyaconitine A, ephedrine, pilocarpine, lobeline, ergometrine, anabasine, oxymatrine, theophylline, colchicine, tetrahydropalmatine, and eserine, were performed by using ESI+ in multiple-reaction monitoring (MRM) mode. Under the optimized conditions, the calibration curves of the 17 compounds presented good linearity (r≧0.9952) in the ranges of 0.5–50 µg/L and 0.5–500 µg/L. The quantitation limits (LOQs) and detection limits (LODs) ranged from 0.5–1 and 0.1–0.5 µg/L, respectively. The average extraction recoveries were obtained in the range of 81.7–102.3%. The intra-day and inter-day relative standard deviations (RSDs) were less than 10% and 15%, respectively. The results indicated that the method was simple, rapid, selective, sensitive, and stable enough to examine toxic alkaloids and was suitable for poisoning diagnosis and forensic toxicology.