Direct online HPLC-CV-AFS method for traces of methylmercury without derivatisation: a matrix-independent method for urine, sediment and biological tissue samples

Abstract

Mercury (Hg) is a global pollutant which occurs in different species, with methylmercury (MeHg) being the critical compound due to its neurotoxicity and bioaccumulation through the food chain. Methods for trace speciation of MeHg are therefore needed for a vast range of sample matrices, such as biological tissues, fluids, soils or sediments. We have previously developed an ultra-trace speciation method for methylmercury in water, based on a preconcentration HPLC cold vapour atomic fluorescence spectrometry (HPLC-CV-AFS) method. The focus of this work is mercury speciation in a variety of sample matrices to assess the versatility of the method. Certified reference materials were used where possible, and samples were spiked where reference materials were not available, e.g. human urine. Solid samples were submitted for commonly used digestion or extraction processes to obtain a liquid sample for injection into the analytical system. For MeHg in sediment samples, an extraction procedure was adapted to accommodate MeHg separation from high amounts of Hg(2+) to avoid an overload of the column. The recovery for MeHg determination was found to be in the range of 88-104% in fish reference materials (DOLT-2, DOLT-4, DORM-3), lobster (TORT-2), seaweed (IAEA-140/TM), sediments (ERM(®)-CC580) and spiked urine and has been proven to be robust, reliable, virtually matrix-independent and relatively cost-effective. Applications in the ultra-trace concentration range are possible using the preconcentration up to 200 mL, while for higher MeHg-containing samples, lower volumes can be applied. A comparison was carried out between species-specific isotope dilution gas chromatography inductively coupled plasma mass spectrometry (SSID-GC-ICP-MS) as the gold standard and HPLC-CV-AFS for biological tissues (liver, kidney and muscle of pilot whales), showing a slope of 1.008 and R (2) = 0.97, which indicates that the HPLC-CV-AFS method achieves well-correlated results for MeHg in biological tissues.

Atomic Spectrometry Update: review of advances in elemental speciation

“…151 In this device Hg species were reduced to Hg 0 with UV-generated electrons, in the presence of 10% formic acid at pH 3, at the conduction band of nano-ZrO 2 for detection by AFS. 154 The recovery for MeHg determination was found to be in the range of 88-104% for ve aquatic CRMs (DOLT-2, DOLT-4, DORM-3, TORT-2, IAEA-140) and spiked urine. Prior to reduction the Hg species in sample extracts were separated on a C 18 column with a mobile phase of 65% CH 3 CN-35% H 2 O containing 1.5 mmol L À1 APDC at pH 5.5 owing at 0.5 mL min À1 .…”

Atomic spectrometry update – a review of advances in environmental analysis

“…3.3.3 Atomic uorescence spectrometry. A direct on-line HPLC-CV-AFS method 257 for the determination of MeHg in water was shown also to be applicable to urine, sediment and biological samples. The method was adapted for each sample matrix to address the different challenges posed.…”

Mercury Toxicity and Speciation Analysis

“…Setback of HPLC is generally higher LODs, unless micro-or nano-HPLC is used. Use of sample preconcentration can improve this drawback; Brombach et al achieved LODs of 1.5 ng l −1 for Hg speciation in urine samples using CV-AFS [83]. However, often used buffer solutions with high salt content or molarity limit the compatibility with ICP-MS. Table 9.2 provides an overview of Hg speciation techniques.…”