An evaluation of extraction techniques for arsenic species from freeze-dried apple samples

The extraction of arsenic from freeze-dried apples and subsequent determination of individual arsenic species by HPLC-ICP-MS is described. Solvent extraction with sonication using various aqueous and aqueous/solvent mixtures was initially evaluated by measuring total arsenic extracted by ICP-MS. A two step procedure using overnight treatment with alpha-amylase enzyme followed by sonication for 6 h with 40:60 acetonitrile-water was found to provide good extraction efficiency. The concentration of arsenic extracted was compared with the concentration of total arsenic in the samples determined using ICP-MS after microwave digestion in order to calculate extraction efficiency. Individual arsenic species in the extracts were measured using HPLC-ICP-MS. The three most abundant arsenic species found were arsenite, arsenate and dimethylarsinic acid. Total arsenic concentrations in the freeze-dried apple samples ranged from 8.2 to 80.9 micrograms kg-1 As, dry mass. By HPLC-ICP-MS, the relative amount of inorganic arsenic in the samples ranged from 73 to 90% of the sum of the arsenic species detected in each sample.