Separation of Organoarsenicals by Means of Zwitterionic Hydrophilic Interaction Chromatography (ZIC®-HILIC) and Parallel ICP-MS/ESI-MS Detection

An analytical scheme was developed for the separation and detection of organoarsenicals using a zwitterionic stationary phase of hydrophilic interaction chromatography (ZIC®-HILIC) coupled in parallel to electrospray ionization mass spectrometry (ESI-MS) and to inductively coupled plasma mass spectroscopy (ICP-MS). The optimization of separation and detection for organoarsenicals was mainly focused on the influence of the percentage of acetonitrile (MeCN) used as a major component of the mobile phase. Isocratic and gradient elution was applied by varying the MeCN percentage from 78 % to 70 % MeCN and 22 % to 30 % of an aqueous solution of ammonium acetate (125 mM NH4Ac; pH 8.3) on a ZIC®-HILIC column (150 × 2.1 mm id, 3.5 μm), to allow for the separation and successful detection of nine organoarsenicals (i.e., 3-nitro-4-hydroxyphenylarsonic acid (roxarsone, Rox), phenylarsonic acid (PAA), p-arsanilic acid (p-ASA), phenylarsine oxide (PAO), dimethylarsinate (DMA), methylarsonate (MMA), arsenobetaine (AsB), arsenocholine (AsC) and trimethylarsine oxide (TMAO)) within 45 min. All analytes were prepared in the mobile phase. The flow rate of the mobile phase, the splitting ratio between ICP-MS and ESI-MS detection, and the oxygen addition were adapted to ensure that there appeared a stably burning inductively coupled plasma. Furthermore, the analytical method was evaluated by the identification and quantification of AsB in the reference material DORM-2 (dogfish muscle) resulting in a 95-% recovery with respect to the AsB concentration in the extract.