Characterization Of Organic Acids And Esters By On-line Derivatization Gas Chromatography/Mass Spectrometry In The Presence Of Organic Alkali

The on-line derivatization gas chromatography(GC)technique is particularly suitable for the analysis of the high-molecular weight samples containing ester and polar components such as fatty acids,ginkgolic acids and triglycerides.The analytes mixed with organic alkali reagent such as tetramethylammonium hydroxide(TMAH)and injected into the heated injected port or pyrolysis,followed by GC analysis.The respective methyl derivatives products formed in the derivatization reaction are more suitable for GC analysis.In this work,the on-line derivatization technique was applied for the determination of organic acids and esters in plants,biodiesel,foods and environmental samples.Chapter one mainly focused on the history of derivatization technique,derivative mechanism,organic alkali reagents and the devices for the derivatization reaction as well as its applications in lipids,archaeological identification,environmental chemistry,synthetic polymers,natural products,life sciences and medicine,biological analysis and soil/sediment.In chapter two,on-line methylation gas chromatogrphy(OM-GC)in the presence of trimethylsulfonium hydroxide(TMSH)was developed to the quantitative analysis of alkylphenols.It was demonstrated that OM-GC with TMSH enables the highly sensitive determination of a total of 9 alkylphenols including polyunsaturated ginkgolic acid GA17:2 in Ginkgo biloba sarcotesta as their methyl derivatives on the resulted pyrograms with a DB-23 column.Compared with the HPLC method,the main advantages are simple operation,without any tedious and time-consuming pretreatment.The information of the positional double bond isomers of ginkgolic acids and the components of ginkgols can be obtained by the OM-GC method.In chapter three,thin layer chromatography combined with on-line hydrolysis methylation gas chromatogrphy(TLC-OHM-GC)were developed for the determination of free acids and glycerides in biodiesel samples.The solvent extraction(SE)technique and thermal desorption(TD)technique were applied to desorbed the acids and glyceride components on the silica gel of TLC.And then,the desorbed components were analyzed by the OHM-GC.The results show that the TLC-TD-OHM-GC method has the advantage of simple operation,save solvents and environmentally friendly.In chapter four,derivatization at injection port following hollow fiber-based liquid-liquid-liquid microextraction(HF-LLLME)with tetramethylammonium acetate(TMAAc)for the simultaneous determination of benzoic acid and sorbic acid in food samples and environmental water samples by gas chromatography(/mass spectrometry)(GC(/MS))has been described.In this method,TMAAc served two purposes.First,it used as the acceptor solution for extraction of acidic analytes of benzoic acid and sorbic acid at HF-LLLME step.Second,it used as derivatization reagent for the methyl derivatization of the acidic analytes on the GC injection port.The proposed method is a simple,rapid,accurate and sensitive method for the determination of benzoic acid and sorbic acid in various samples with complex matrix.In addition,the detection sensitivities of benzoic acid and sorbic acid by GC were dramatically improved.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.