Speciation of mercury in water and freshwater fish samples using two-step hollow fiber liquid phase microextraction with electrothermal atomic absorption spectrometry

Abstract

A novel method for trace inorganic mercury (Hg2+) and methylmercury (MeHg) speciation was developed utilizing two-step hollow fiber liquid phase microextraction (two-step HF-LPME) procedures with two/three phases combined with electrothermal atomic absorption spectrometry (ETAAS). This allowed for consecutive determination of MeHg and Hg2+ in water and fish samples. MeHg was firstly extracted into a polypropylene hollow fiber containing toluene by HF(3)-LPME, Na2S2O3 was then injected inside the fiber lumen as an acceptor phase to trap the analyte, while Hg2+ still existed in the aqueous solution. For Hg2+ determination, HF(2)-LPME procedure was subsequently applied after Hg2+ was chelated with diethyldithiocarbamate (DDTC) and then Hg2+-DDTC was extracted using 1-octanol. The key parameters and ETAAS profiles were investigated and optimized. This method was then applied to mercury speciation in several real-world samples and the recoveries of these samples including a standard reference material (SRM-1566b). This led to LODs of 0.14 and 0.06 μg L−1 with 2.3 and 3.7% RSD (n = 6) achieved with enrichment factors of 103 and 95 for Hg2+ and MeHg, respectively. The developed method was then evaluated and compared to other analytical techniques for mercury determination in water and fish samples.