A simple method for the speciation analysis of bio-accessible arsenic in seafood using on-line continuous leaching and ion exchange chromatography coupled to inductively coupled plasma mass spectrometry

Abstract

A quick and simple on-line leaching method was used to assess the maximum bio-accessibility of As in seafood samples. Artificial saliva, gastric juice and intestinal juice were successively pumped through a mini-column of sample (maintained at 37 °C in a thermostatically controlled water bath), which is connected to the nebulizer of an inductively coupled plasma mass spectrometry (ICP-MS) instrument. In contrast to the usual batch method, this approach allows the continuous monitoring of the progressive release of As by the 3 reagents. Thus, the dissolution equilibrium is driven to the right, thereby enabling the determination of the maximum amount of analyte that can be dissolved (i.e. the worst-case scenario). Results for 4 certified reference materials (CRMs) show that saliva alone was sufficient to release, in less than 5 min, all the bio-accessible total As that was mobilised by saliva and gastric juices in the batch mode. The As speciation in each leachate was then determined by ion-exchange chromatography (IEC) coupled to ICP-MS, after adjustment to the gradient program previously optimised by experimental design, along with a 5-fold sample dilution and increased stabilisation time. Under these optimised conditions, 7 different arsenic species in saliva could be separated within 18 min in a single chromatographic run. In all cases, the sum of bio-accessible and residue As concentrations agreed with the certified value. Bio-accessible speciation results were compared and discussed with those previously reported by different extraction methods in the literature.