Study On Analytical Method Of Perchlorate And Application In Tea

The presence of perchlorate in Chinese tea is an escalating problem that has aroused public concern over potential health hazards.Analytical techniques such as ion chromatography(IC),ion chromatography-mass spectrometry(IC-MS),and LC-mass spectrometry(LC-MS)allow for the accurate determination of perchlorate in tea samples.The determination methods,such as IC/IC-MS/LC-MS,often are not satisfied with the sensitivity requirement,or can't eliminate the effects from complex matrix.This dissertation consists of five parts.The first chapter summarized the background related to perchlorate.The second chapter summarized the progress of perchlorate analysis in food.The third part is the introduction of Chinese tea export and perchlorate contamination in tea.The forth chapter is the main body of the thesis in which compared with three kinds of methods for the determination of perchlorate in tea.Ion chromatography is not suitable for the determination of perchlorate in tea because it was not found.The method of ion chromatography-mass spectrometry(IC-MS)is simple and satisfied with the determination requirement of perchlorate in tea.The chromatographic analysis was performmed on Dionex 5000+ instrument,using high capacity and hydroxide selective column IonPac AS20 by a gradient elution.Perchlorate was seperated by KOH elution generated from on-line Eluent Generation Cartridge.MSQ Plus? as a detector scaned samples in the negative ESI for confirmation and quantification.The results display good linearity in the range of 0.5~20.0 ?g/L for all compounds,with correlation coefficients r>0.9998.The relative standard deviations RSD were 2.71%(n = 5)and the limit of quantification of the method was 0.025 mg/kg.The average recoveries of perchlorate in the 4 kinds of tea ranged from 91.6% to 114.4%.In order to develop the possibility for the higher sensitivity,TSQ Quantiva? was configured as a detector to scan samples in the negative ESI and multiple reaction monitoring(MRM)mode.The results showed that IC-MS/MS was more sensitive and higher level of recoveries for perchlorate determination in various of complex samples such as tea,and with good linearity in the range of 0.02~10.0 ?g/L.Meanwhile,the correlation coefficients r>0.9991 and the RSD were 2.67%(n = 5),with the limit of quantification of 0.002 mg/kg.