Rapid speciation of methylated and ethylated mercury in urine using headspace solid phase microextraction coupled to LC-ICP-MS

Abstract

Solid-phase microextraction coupled to liquid chromatography-inductively coupled plasma-mass spectrometry (SPME-LC-ICP-MS) is presented as a new approach for the extraction and speciation of methylmercury (MeHg) and ethylmercury (EtHg) in a complex urine matrix. Despite the fact that urine is one of the most easily accessible sources of biological specimens for clinical testing, reports of mercury speciation methods are limited. Without any tedious sample pretreatments or derivatization procedures, headspace SPME offers a clean and convenient one-step extraction followed by direct desorption into HPLC. In this work, the fibre was first exposed to the sample headspace for a 45 min extraction, followed by a 5 min desorption. Experimental parameters including extraction time and temperature, sodium chloride salt concentration, agitation rate and desorption time were optimized to achieve detection limits down to 0.06 μg L−1 for both organomercury species. Sample recoveries in spiked urine matrix ranged from 81.7–109.5%. The accuracy of the method was further validated using a certified reference material (TORT-2) and applied in the organomercury speciation of urine samples collected from patients with suspected mercury poisoning.