Hollow fiber supported ionic liquid membrane microextraction for speciation of mercury by high-performance liquid chromatography-inductively coupled plasma mass spectrometry

摘要

With an ionic liquid as the membrane liquid and dithizone as the carrier, a novel and simple hollow fiber supported liquid phase microextraction (HF-LPME) method was developed for the preconcentration and determination of monomethylmercury (MMHg) and inorganic mercury (IHg) in environmental water samples by high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS). The parameters affecting the enrichment factors, including the type of ionic liquid membrane and carrier, the pH of the sample solution, the concentration of L-cysteine in the acceptor phase, stirring rate, extraction temperature and time, were optimized. With the optimal extraction conditions (ionic liquid membrane phase: [C4MIM][PF6] with 0.02% (m/v) dithizone; acceptor phase: 25 ??L, 1 g La?’1L-cysteine; extraction temperature: 50 ?°C; extraction time: 12 h), the obtained enrichment factors of MMHg and IHg were 1620 and 1540, and the detection limits for MMHg and IHg were 0.3 ng La?’1 and 0.9 ng La?’1, respectively. There was no significant effect on the extraction efficiency in the presence of humic acid (0a€“25 mg La?’1 dissolved organic carbon). The proposed method was applied to real water samples, and the spike recoveries obtained were in the range 90.8a€“108.2%. These results demonstrate that the proposed ionic liquid based HF-LPME-HPLC-ICP-MS method is a simple and sensitive technique for the determination of mercury species at trace levels in water samples, with a high reproducibility and accuracy.