DETERMINATION OF TOTAL ARSENIC CONCENTRATIONS IN BIOLOGICAL MATRICES BY INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY

The importance of trace element speciation in the assessment of the nutritive benefit or toxicological threat of a given trace element is becoming more widely appreciated. In order to be able to furnish meaningful results, the analyst must first be able to determine accurately the total concentration of the element in a given matrix and the sum of the species concentrations must be equal to the total concentration, within experimental error. Whilst participating in some preliminary As speciation studies organized by the European Unions' Measurement and Testing group it was observed that total As levels were in excess of their certified or indicative values. The source of this error has been identified as arising principally from differences in acidity between the samples and external calibrants, In the course of this study, an element-specific enhancement of As was observed (up to a factor of 5) and a hypothesis to explain this observation is suggested. Accurate results were obtained using a matrix matching technique which minimized differences in acidity and carbon loading.