Rapid and robust speciation/quantitative analysis of arsenous acid and related metabolites in serum by liquid chromatography–inductively coupled plasma-tandem mass spectrometry

Purpose Arsenic, especially inorganic trivalent species, is one of the most important poisons in the field of forensic toxicology. There are many reports on the speciation analysis of arsenic species in biological specimens by liquid chromatography–inductively coupled plasma-mass spectrometry (LC–ICP-MS). The aim of this study was to develop a rapid and robust analytical method for speciation/quantitative analysis of arsenic species in serum by LC–ICP-tandem mass spectrometry (MS/MS). Methods An analytical method for arsenous acid and its metabolites, dimethylarsinic acid, monomethylarsonic acid, and arsenic acid in serum was tested through the analysis of serum samples by an LC–ICP-MS/MS system consisting of different anion exchange columns and different mobile phases. Rapid pretreatment of serum samples by ultrafiltration was also tested. Results Robust speciation/quantitative analysis of arsenic in serum samples with LC–ICP-MS/MS was achieved by using a mildly acidic mobile phase. The limits of detection for the four arsenic species were in the range 0.19–0.68 ngAs/mL, and the well-known interference by argon chloride ion was removed by the MS/MS apparatus. This method was precise enough for quantitative analysis of four arsenic compounds in serum (0.24–3.68% precision; 97.0–104% accuracy; and 101–112% recovery for all analytes at 5 and 50 ngAs/mL). The total analytical time was 30 min (20-min pretreatment and 10-min analysis), and multiple serum samples could be pretreated simultaneously. Conclusions A rapid, sensitive, interference-free and robust speciation/quantitative analysis of toxic arsenous acid and related metabolites in serum by LC–ICP-MS/MS was developed. To our knowledge, this is the first report to use LC–ICP-MS/MS for analysis of arsenic species in human blood/serum samples.