Ultrasensitive speciation analysis of mercury in waters by headspace solid-phase microextraction coupled with gas chromatography-triple quadrupole mass spectrometry

Abstract

A sensitive, repeatable and inexpensive method combining headspace solid-phase microextraction (HS-SPME) with gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) was developed for the simultaneous speciation of mercury in water samples at trace and ultra-trace levels. The low-cost home-made polydimethylsiloxane (PDMS) fiber based on sol-gel method was used as a substitute for commercial one to extract and enrich the derivatives of inorganic mercury (Hg2+), methylmercury (MeHg) and ethylmercury (EtHg) in the headspace after derivatizing with sodium tetraphenylborate (NaBPh4) in situ. Some important parameters, such as preincubation and extraction temperature, preincubation time, extraction time and inlet temperature, were investigated. Under the optimized conditions, the limits of detection (LODs) of alkyl mercury and inorganic mercury were 0.03 and 6 ng L–1, respectively. The correlation coefficients were more than 0.994 in the range of 25.0–200 ng L–1 for Hg2+ and 0.12–80.0 ng L–1 for alkyl mercury. The recoveries of the analytes in real water samples spiked at three levels were all in the range of 76.6%-114.8%. The repeatability of all mercury species was good. For inorganic mercury spiked at the lowest quality control concentration (LQC) level, the relative standard deviation (RSD) was 12.1%, and it was less than 7.7% at higher spiked concentration. The RSDs of alkyl mercury were in the range of 3.0–8.5%. The method validation demonstrated the applicability of the proposed method, and it was finally used for the determination of mercury species in surface water and wastewater samples.