Study On Speciation Analysis Method Of Arsenic And Mercury Based On A Novel In-line Enrichment Technology

In recent years,with the rapid development of industry and agriculture,especially the illegal discharge of a large number of"three waste",urban sewage and domestic waste dumping and the abuse of agricultural inputs,heavy metal pollution has become one of the most serious environmental and food safety problems.The toxicity of heavy metal elements not only depends on the total amount,but also on the form of its existence.Therefore,the accurate and quantitative element form is of great significance to ensure the food safety in China.Currently,LC-AFS has the advantages of simple structure,low instrument and operating cost,which has become one of the most common hyphenated technologies in element morphology analysis.However,there are also certain limitations with LC-AFS.For example,the detection ability of trace/ultra-trace As(V)and mercury species is limited in the analysis of real samples.In order to improve the sensitivity of LC-AFS,this study constructed two in-line enrichment systems and their application methods:an LC-HG-in situ DBDT-AFS method for enrichment and determination of inorganic arsenic in rice based on post-column gas phase enrichment;and an in-line C₁₈microcolumn-LC-AFS method for enrichment and analysis of mercury forms in water and rice based on pre-column liquid phase enrichment technique.The main research contents are as follows:1.Based on the in situ gas phase enrichment technology,the LC-HG-in situ DBDT-AFS system was constructed,and the key parameters of DBDT pre-enrichment,such as capture gas flow rate and voltage,purge time,and release gas flow rate and voltage were optimized,and finally the air flow rate of 110m L/min and voltage of 11 k V were selected for capture;the interfering substances were removed by Ar purge for 190 s before release;the 180 m L/min H₂flow rate and voltage of 13 k V were selected for release.2.A method for the determination of inorganic arsenic in rice by LC-HG-in situ DBDT-AFS was developed.Under the optimized conditions,the linear range of the established LC-HG-in situ DBDT-AFS method was 0.5?50?g/L with R²>0.997,and the LOD of inorganic arsenic was 0.051?g/L(injection volume=100?L)with an enrichment multiple of 11.The results were verified by rice standards within the reference value,and there was no significant difference when compared with LC-ICP-MS,and the spiked recoveries of the actual samples were 93%?102%,indicating that the method can be applied to the study of inorganic As detection in rice.3.Based on the pre-column liquid-phase enrichment technology,the inline SPE enrichment-LC-AFS system was constructed.The in-line SPE enrichment device was designed and the relevant parameters of LC-AFS were optimized.4.The in-line C₁₈microcolumn-LC-AFS method was developed for the determination of mercury forms in water and rice.In this study,the enrichment conditions such as modified solution concentration,adsorbent capacity,injection volume,eluent type,flow rate and sample p H were optimized;the performance of the system was evaluated under the optimal conditions,and the results showed that R²>0.999 for Hg forms at 5?1000 ng/L.The LOD of Hg²⁺and Met Hg is 0.3 and 0.2 ng/L.When the injection volume is 10 m L,the enrichment factors of Hg²⁺and Met Hg are 91 and 94,respectively.And the RSD of the standard solutions were 2%.The recoveries of the actual water samples and rice spiked were 92%?106%,indicating that the method can be applied to the enrichment detection of Hg speciation in water and rice.