Dithizone-functionalized solid phase extraction–displacement elution-high performance liquid chromatography–inductively coupled plasma mass spectrometry for mercury speciation in water samples

A novel and simple solid phase extraction (SPE)-high performance liquid chromatography (HPLC)–inductively coupled plasma mass spectrometry (ICP-MS) method was developed for determination of inorganic mercury (IHg), methylmercury MeHg and ethylmercury (EtHg) in water samples in the present work. The procedure involves pre-functionalization of the commercially available C18 SPE column with dithizone, loading water sample, displacement elution of mercury species by Na2S2O3 solution, followed by HPLC–ICP-MS determination. Characterization and optimization of operation parameters of this new SPE procedure were discussed, including eluting reagent selection, concentration of eluting reagent, volume of eluting reagent, effect of NaCl and humic acid in sample matrix. At optimized conditions, the detection limits of mercury species for 100 mL water sample were about 3 ng L−1 and the average recoveries were 93.7, 83.4, and 71.7% for MeHg, IHg and EtHg, respectively, by spiking 0.2 μg L−1 mercury species into de-ion water. Stability experiment reveals that both the dithizone-functionalized SPE cartridge and the mercury species incorporated were stable in the storage procedure. These results obtained demonstrate that SPE-HPLC–ICP-MS is a simple and sensitive technique for the determination of mercury species at trace level in water samples with high reproducibility and accuracy.