Hyphenation of high performance liquid chromatography with sector field inductively coupled plasma mass spectrometry for the determination of ultra-trace level anionic and cationic arsenic compounds in freshwater fish

Abstract

We describe a hyphenation technique between HPLC and ICP-SFMS for ultra-trace arsenic speciation analysis. Exceptional analytical performance was achieved using a MicroMist nebulizer preceded by a high-pressure splitter. Despite a 1 ∶ 7.5 flow splitting, the detection limits in the range of 1.2 to 2.4 pg mL⁻¹ were about two times lower than those obtained with a concentric nebulizer without any flow splitting, demonstrating the applicability of coupling conventional HPLC system (1.5 mL min⁻¹ eluent flow) with microflow nebulizer for ultra-trace arsenic speciation analysis. This set-up offers an advantage for on-line fraction collection for either multidimensional chromatographic separation of co-eluting As compounds or for structural identification of unknown compounds without sacrificing analytical sensitivity. In addition, this system showed good accuracy and repeatability. The method was applied to the determination of arsenic compounds in freshwater fish samples from an arsenic-rich lake, Moira Lake, Canada. Using cation-exchange chromatography, tetramethylarsonium ion (Tetra) was detected in freshwater fish samples for the first time. Moreover, in pumpkinseed, Tetra was found to be the major arsenic species, indicating that the biomethylation pathway in freshwater ecosystems may include the tetramethyl stage.