title: Comparative oxidation state specific analysis of arsenic species by high-performance liquid chromatography-inductively coupled plasma-mass spectrometry and hydride generation-cryotrapping-atomic absorption spectrometry.
abstract: The formation of methylarsonous acid (MAsIII) and dimethylarsinous acid (DMAsIII) in the course of inorganic arsenic (iAs) metabolism plays an important role in the adverse effects of chronic exposure to iAs. High-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) and hydride generation-cryotrapping-atomic absorption spectrometry (HG-CT-AAS) have been frequently used for the analysis of MAsIIIand DMAsIIIin biological samples. While HG-CT-AAS has consistently detected MAsIIIand DMAsIII, HPLC-ICP-MS analyses have provided inconsistent and contradictory results. This study compares the capacities of both methods to detect and quantify MAsIIIand DMAsIIIin anin vitromethylation system consisting of recombinant human arsenic (+3 oxidation state) methyltransferase (AS3MT), S-adenosylmethionine as a methyl donor, a non-thiol reductant tris(2-carboxyethyl)phosphine, and arsenite (iAsIII) or MAsIIIas substrate. The results show that reversed-phase HPLC-ICP-MS can identify and quantify MAsIIIand DMAsIIIin aqueous mixtures of biologically relevant arsenical standards. However, HPLC separation of thein vitromethylation mixture resulted in significant losses of MAsIII, and particularly DMAsIIIwith total arsenic recoveries below 25%. Further analyses showed that MAsIIIand DMAsIIIbind to AS3MT or interact with other components of the methylation mixture, forming complexes that do not elute from the column. Oxidation of the mixture with H2O2which converted trivalent arsenicals to their pentavalent analogs prior to HPLC separation increased total arsenic recoveries to ~95%. In contrast, HG-CT-AAS analysis found large quantities of methylated trivalent arsenicals in mixtures incubated with either iAsIIIor MAsIIIand provided high (>72%) arsenic recoveries. These data suggest that an HPLC-based analysis of biological samples can underestimate MAsIIIand DMAsIIIconcentrations and that controlling for arsenic species recovery is essential to avoid artifacts.
authors.affiliation: Curriculum in Toxicology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7461, USA.
authors.forename: Jenna
authors.initials: J
authors.lastname: Currier
authors.forename: R Jesse
authors.initials: RJ
authors.lastname: Saunders
authors.forename: Lan
authors.initials: L
authors.lastname: Ding
authors.forename: Wanda
authors.initials: W
authors.lastname: Bodnar
authors.forename: Peter
authors.initials: P
authors.lastname: Cable
authors.forename: Tomáš
authors.initials: T
authors.lastname: Matoušek
authors.forename: John T
authors.initials: JT
authors.lastname: Creed
authors.forename: Miroslav
authors.initials: M
authors.lastname: Stýblo