Multielement electrochemical vapor generation system coupled with atomic fluorescence spectrometer for simultaneous measurement of trace levels of As and Hg in coastal seawater samples

Background: Toxic elements As and Hg in coastal waters affect human health through the food chain even at trace levels. The simultaneous determination of As and Hg in seawater using electrochemical vapor generation (ECVG) with atomic fluorescence spectrometer (AFS) currently has technical bottlenecks. One is the need for a simple and efficient chemical reaction cell and corresponding parameters to generate both AsH₃ and Hg vapors, and the other is a suitable preservation method of the mixed standard solutions.

Results: A novel, efficient, online ECVG device was developed and interfaced with a laboratory-built multichannel AFS. The electrolytic cell adopted Sn-Pb alloy as the cathode material to generate both AsH₃ and Hg vapors by electrolysis, replacing the unstable reagent tetrahydroborate (THB) usually used in most traditional vapor generation methods. The AFS was equipped with a built-in H₂ generator for fuel supply, instead of the conventional acid-THB system. A mixed standard solution of As and Hg was prepared and preserved using thiourea-ascorbic acid as a fixing agent for Hg and a prereduction agent for As(V). The method detection limits (LOD, 3σ) were 0.005 and 0.003 μg/L for As and Hg, respectively. The relative standard deviations (RSD, n = 8) of the spiked samples were 2.8 % (0.50 μg/L As) and 3.1 % (0.05 μg/L Hg), respectively. The recoveries of standard spiked seawater samples with different salinities ranged from 86.1 % to 115.3 %.

Significance: The system has been successfully applied to the simultaneous analysis of As and Hg in the seawater samples collected from the Xiamen coastal area. The study results provide a sensitive, accurate, and efficient method to promote the development and utilization of simultaneous analysis of multielement in seawaters.