Tudies On The Phenolic Acids By On-line Derivatization Gas Chromatography/mass Spectrometry

On-line derivatization gas chromatogrphy/mass spectrometry is a new technology.The polar compounds containing hydroxyl,carboxylic acid,amine or thiol functional groups were derivatized to their methyl esters by derived reagents in the GC injection port.The paper studies the main influencing factors for derivatization and extraction efficiency.And a method of derivatization at injection port following three phase hollow fiber microextraction for the simultaneous determination of phenolic acids in beers by gas chromatography was developed.Chapter one mainly focused on two aspects:1.The history,chemical process,derived reagents and the devices for the on-line derivatization;2.The extraction mode and main influencing factors for the hollow fiber microextraction.In chapter two,in order to get the highest derivatization efficiency of p-cresol,p-chlorophenol,p-tert-butyl-phenol by on-line derivatization gas chromatogrphy/mass spectrometry.Several parameters related to the derivatization efficiency were optimized.The optimized conditions were as follows:reaction temperature was 300?,derived reagents was TMAH.In chapter three,a method of derivatization at injection port following three phase hollow fiber microextraction with tetramethylammonium hydroxide(TMAH)as a dual-function regent,for the simultaneous determination of salicylic acid,p-hydroxybenzoic acid,cinnamic acid,vanillic acid,p-coumaric acid and ferulic acid in beers by gas chromatography was developed.In this method,phenolic acids were extracted from aqueous samples to a thin layer of organic solvent(hexyl acetate)phase impregnated into the pores of the hollow fiber wall,and then back extracted to an acceptor solution(TMAH)located inside the lumen of the hollow fiber.Upon injection,the phenolic acids were derivatized to their methyl esters in the GC injection port.Several parameters related to the derivatization and extraction efficiency(i.e.,extraction solvent,the derivatization reagent and acceptor solvent,PH,salt content,stirring rate,extraction time and extraction temperature)were optimized.Under the optimal conditions,the linear range of phenolic acids were 0.50?15.00 mg/L,the limits of detection were 0.05?0.18 mg/L.The proposed method was applied to the determination of the phenolic acids in beers.Vanillic acid,p-coumaric acid and ferulic acid were found,others were not detected.The spiked average recoveries were 90.1%?106.8%and RSD%was less than 5.9%(n=3).The method is suitable for the determination of phenolic acids in beers.In the last chapter,the main results obtained from this research were summarized.Then,the problems to be considered for this research and the possible future trends in this field were also discussed.