Separation of organic and inorganic arsenic species by HPLC-ICP-MS

The HPLC separation of eight anionic, cationic or neutral arsenic species ( arsenite, arsenate, monomethylarsonic acid, dimethylarsinic acid, arsenobet aine, arsrnocholine, trilmethylarsine oxide and tetramethylarsonium ion) on a high-capacity, anion-exchange column (Ion Pac AS 7, Dionex) was studied. The separation was performed during one run with a nitric acid gradient ra nging from pH 4-1.3. The influence of sodium dodecyl sulfate (SDS), sodium octyl sulfate (SOS) and 1,2-benzenedisulfonic acid (BDSA) as ion pairing el uent modifiers was investigated. In addition the effect of elevated tempera tures (30 to 40 degrees C) was studied. The best results were obtained at r oom temperature of 20 degrees C with 0.05 mM benzenedisulfonic acid as the eluent modifier. The chromatograph was connected to an ICP-MS via a cross-f low nebulizer. Detection limits obtained with the optimized chromatographic separation were 0.16-0.60 mu g As L-1 for different species. The proposed speciation method was applied to the determination of arsenic species in th e DORM-2 reference material (Doefish Muscle) and in aqueous extracts of mus hrooms collected on arsenic contaminated ground.