Arsenic extraction and speciation in carrots using accelerated solvent extraction, liquid chromatography and plasma mass spectrometry

Arsenic present in freeze-dried carrots was extracted using accelerated sol vent extraction (ASE). Several parameters, including selection of the dispe rsing agent, extraction time, number of extraction cycles, particle size an d extraction temperature, were evaluated to optimize the ASE method. Filter ing and treatment with C-18 SPE cartridges were also evaluated as part of t he sample preparation procedure before speciation analysis. The method was validated by spiking single arsenical and mixed arsenical standards on the dispersing agent and on portions of freeze-dried carrot prior to extraction . LC-ICP-MS was used to determine individual arsenic species in the carrot extracts. A weak anion-exchange column was used for the separation of As(ii i), As(v), monomethylarsonic acid (MMA), dimethylarsinic acid and arsenobet aine. Optimized sample preparation conditions were applied to the extractio n of arsenic in nine freeze-dried carrot samples. Total arsenic concentrati on in the carrot samples ranged from less than 20 ng g(-1) to 18.7 mug g(-1 ), dry mass. Extraction efficiency, defined as the ratio of the sum of indi vidual arsenic species concentrations to total arsenic, ranged from 80 to 1 02% for freeze-dried carrots with arsenic concentrations greater than the l imit of quantitation. Inorganic As(iii) and As(v) were the only species fou nd in samples that contained less than 400 ng g(-1) total arsenic. MMA and an unidentified arsenic compound were present in some of the samples with h igher total arsenic content.