Synthesis Of Several N-substituted Maleimide Thiol-derived Reagents And Their Analytical Applications

Maleimides are excellent derivative reagent for thiols selective label and quantitation.In the reaction of maleimide and thiols,the thiol is added across the double bond of the maleimide to yield a stable thioether.The derivative reaction can be performed under milder conditions within 10 minutes.Due to the double bond of maleimide structure has strong electron-withdrawing effect and the fluorophore attached thereto has an electron-donating action,there exists a photo-induced charge transfer(PET)phenomenon between the maleimide group and the fluorophore.Under the excitation of light,the electrons are transferred from the fluorophore into the empty electron orbit of the maleimide group so that the electrons excited by the light cannot directly migrate to the original state orbit to emit fluorescence,which leads to the quenching of the fluorescence.When the thiols binding with maleimide,the ability to bind electrons is reduced and the PET process is inhibited.The electrons excited by the light in the fluorophore can directly migrate back to the original state orbit,thereby enhancing the fluorescence emission.This enhancement of fluorescence only after the reaction makes it a unique advantage.In this paper,three maleimide thiols pre-column derivatization reagents were designed and synthesized,and then the synthesized reagents were used in environmental detection and food detection to establish a high selectivity,sensitivity and accuracy high performance liquid chromatography(HPLC-MS)method and high performance liquid chromatography-mass spectrometry(HPLC-MS/MS)method.Specific work is as follows: Chapter one: Brief introduction to the characteristics of maleimide derivative reagents,light induced charge transfer(PET)mechanism,stable isotope-coded derivatization,matrix theory of basic theoretical knowledge.Chapter two: Three novel maleimide thiols-derivative reagents were synthesized and characterized in this work,including carbazole-9-ethyl-2-maleimide,3-(9-ethylcarbazole)-maleimide and isotope-coded derivatization reagent d0/d4-acridone-10-ethyl-2-maleimide.The derivatized reagents show highly sensitive,rapidly reaction rate,and greatly selective and so on.Chapter three: The carbazole-9-ethyl-2-maleimides was used as fluorescent derivative reagents for the determination of thiols contaminants in DiYi River.Because of the PET,the derivatization reagent has no fluorescence,and the fluorescence is recovered after the reaction with thiol.The reagent can greatly reduce the background interference and improve the detection sensitivity in the process of detecting the thiol compound.At the same time,the framework material MOF-5 was used as selective adsorbent in dispersive solid phase extraction(DSPE)to selectively enrich the sulfur-containing compounds in river samples.This method achieves high selectivity and sensitivity analysis of thiols in wastewater.Chapter four: The stable isotope-coded derivatization reagent(SICD)d0/d4-acridone-10-ethyl-2-maleimide was used in the HPLC-MS/MS analysis for the determination of six kinds of thiol in wines.Firstly,the thiols were enriched by the p-HMB assisted solid phase extraction(SPE),then were labeled with SICD.The heavy labeled thiols were used as internal standard.The matrix effect can be greatly eliminated and realize the absolute quantitative of thiols by using stable isotope dilution method.Chapter five: In this chapter,a rapid,sensitive and accurate HPLC-FLD method for the detection of thiols components in coffee was established by using 3-(9-ethylcarbazole)-maleimide as the pre-column derivatization reagent combined with phydroxybromobenzoic acid(p-HMB)assisted fatty acid dispersion liquid-liquid extraction(FA-DLLE).The FA-DLLE method with heptanoic acid as extraction agent,p-HMB assisted extraction,realized the enrichment of thiols aroma components in coffee sample with greatly selective.The method can be used for quantitative and qualitative analysis of thiols in coffee samples.