Determination of arsenic in biological samples by inductively coupled plasma mass spectrometry with selenium as an internal standard

An internal standard method is described for the determination of arsenic in mussel and oyster samples by inductively coupled plasma mass spectrometry. 0.1 g of sample was digested in a microwave oven with addition of 1 mL of HNO3 and 1 mL of H2O2. Se-77 was selected as an internal standard because Se-77 was close to As in mass, the first ionization potential and ion-exchange behavior. In order to eliminate spectral interferences and matrix effects, the analyte was separated from matrix elements using AG2-X8 anion exchange resin. An internal standard method was used for quanti. cation which adopted the isotope dilution procedure assuming Se-77 as a pseudo-isotope of As. The proposed method was validated by analyzing mussel reference material (NIST SRM 2976). The determined As concentration of the reference material agreed well with the certified value within the uncertainty limit. The method was then applied to the analysis of an oyster reference material developed by Korea Research Institute of Standards and Science.