Determination of inorganic As, DMA and MMA in marine and terrestrial tissue samples: a consensus extraction approach

Rationale. Arsenic (As) speciation analysis in biological matrices has been performed for several decades; however, there are very few matrix certified reference materials available for the validation of analytical methods. The literature data on the mass fractions of As species in the existing certified reference materials are inconsistent and suggest method extraction dependency. Methodology. In the present study, an international round-robin study was organised to identify the possible sources of discrepancies in quantitation of several As species in different matrices of biological reference materials: one plant tissue, three marine and three terrestrial biological tissues. Each participating laboratory was provided with a set of identical calibration standard solutions, and analysed the samples by following a common group extraction method as well as using an in-house protocol. Results. The results showed that significant biases can be introduced by insufficient verification of the analyte's mass fractions in the calibration standard solutions. The choice of extraction method seems to have very little impact on the quantitation of As species in the studied plant and terrestrial biological tissues. However, following a prescribed extraction method led to significant reduction of uncertainties in more complex samples such as marine animal tissues. Discussion. Some differences in the mass fractions of As species extracted from marine animal tissues in water (with and without H2O2) were observed and should be further investigated. Despite the variety of extraction methods used, very good agreement between reported mass fractions was achieved and the combined consensus values will be published as certified reference values of As species in the studied materials.