Development And Application Of Online Purge-Trap Hyphenated With Multicollector Inductively Coupled Plasma Mass Spectrometry

Multicollector Inductively Coupled Plasma Mass Spectrometry（MC-ICPMS）is a kind of widely used isotope mass spectrometry,which can determine a variety of metal isotopes with high resolution and high precision.Mercury（Hg）is a global pollutant with high toxicity.The analysis of Hg isotopes using MC-ICPMS is of great importance to trace the environmental processes and sources of Hg.The MC-ICPMS coupled with cold vapor generation（CVG）is the currently used method for determination of Hg isotopes,which requires relatively high concentration of Hg in solution.To analyze Hg isotopes in samples containing relatively low Hg contents,a complex preconcentration procedure is often necessary which tend to time-consuming and cause errors.In this study,an on-line system coupled purge-trap with MC-ICPMS was established.The instrumental interface,data processing method and experimental conditions were designed and optimized in detail.Then,the established on-line system was successfully applied for determination of Hg isotopes in natural water samples.A home-made on-line system coupled MC-ICPMS with purge-trap was established,and the experimental parameters were optimized.Before coupling,the stability and accuracy of MC-ICPMS and purge-trap were tested to make sure each module works right.After the coupled system established,signal acquisition parameters（Sampling time:0.008 s,Sample number:5000 points）and flow parameters（Sample gas:0.89 L/min;Aridus gas:3.98 mL/min,Add gas:0.89 L/min,Purge-trap carrier gas:486 mL/min）were optimized to obtain the optimal Hg isotope signal.Due to the different enrichment efficiencies of two trap tubes,the sample-standard bracketing（SSB）method was optimized as standard-standard-sample-sample-standard-standard bracketing method.To ensure the stability and accuracy of the proposed on-line system,two standards（NIST SRM 3133 and NIST SRM 3177）were measured for many times,respectively.In addition,the data processing methods of transient signals collected from this on-line system were discussed.The precision and accuracy of linear regression slope（LRS）and peak area integration（PAI）were compared.Analytical results were consistent with reported values and had no significant differences by using LRS and PAI,while LRS showed a lower external precision（0.1‰）.Therefore,the established on-line system was accuracy and reliable for Hg isotope analysis,and LRS was selected for data treatment subsequently.The established on-line system was successfully applied for Hg isotope measurement in biological samples and natural water samples.The Hg isotopes in Rapana venosa tissues collected from the Bohai sea(δ²⁰²Hg=-1.96±0.33,Δ¹⁹⁹Hg=-0.32±0.15,2SD),water samples from the Wuhan Ducks Lake(δ²⁰²Hg=-1.47±2.45,Δ¹⁹⁹Hg=0.22±1.00,2SD)and from the East Lake in Wuhan(δ²⁰²Hg=-1.16±4.23,Δ¹⁹⁹Hg=-0.22±1.43,2SD)were determined.