Estimation of the method evaluation function for the determination of hydride-generating arsenic compounds in urine by flow-injection atomic-absorption spectrometry

A direct flow-injection atomic-absorption spectrometric (FIA-AAS) method for the assessment of inorganic arsenic compounds and their metabolites was developed and statistically evaluated by the estimation of the method evaluation function (MEF), which provides detailed information on the analytical performance of the method, i.e., the average combined uncertainty and the magnitude of potential systematic errors. The method evaluation study demonstrated that the use of standard addition was a necessity to obtain an acceptable method performance at low concentrations typical for low dose exposure. In contrast the use of calibration curves resulted in a method with reduced sensitivity and high systematic error. The developed method, using standard addition, had a limit of detection (2.9 microg/l.) sufficiently low for the determination of hydride-generating arsenic species in urine from non-exposed and low exposed persons. Organoarsenicals such as arsenobetaine and arsenocholine are not detected by this method. Hence, the contribution of these compounds derived from a diet containing seafood does not affect the monitoring of inorganic arsenic compounds after occupational or environmental exposure. The high capacity of the FIA-AAS system (three minutes per sample measured by standard addition) together with the low limit of detection makes this method suitable for biological monitoring of inorganic arsenic exposure even though standard addition is required.