Determination of ultratrace selenium and arsenic at parts-per-trillion levels in environmental and biological samples by atomic fluorescence spectrometry with flow injection hydride generation technique

Hydride vapor generation atomic absorption spectrometry (AAS) is a preferre d method for determination of hydride-forming elements such as selenium and arsenic, particularly at ultratrace concentration levels. In this applied research, the hydride vapor generator-coupled atomic fluorescence spectrosc opic system has been used to replace the atomic absorption spectroscopic de tector, which is used in the ordinary hydride generation technique. Also, t he successful analysis of samples using the Bow injection hydride generatio n system (FIA-Hydride) is combined with the atomic fluorescence spectromete r. For better sensitivity, membrane dryers have been used that use a hygros copic, ion-exchange membrane in a continuous drying process between hydride generator (separator) and atomic fluorescence detector to selectively remo ve water vapor from mixed hydride gas streams. The effects of carrier gas B ow rate, different acids, and acid concentrations on sensitivity have been rested to select the best conditions. More than 200 times enhancement of se nsitivity has been shown in the hydride generation atomic fluorescence spec troscopy system (Hydride-AFS). The instrument detection limit (IDL) and met hod detection limit (MDL), which takes into account sample preparation proc ess effects, were determined. Detection levels of a few parts per trillion without a preconcentration stage and clean room are achieved for actual sam ples of selenium and arsenic. The widest linear dynamic range is about four orders of magnitude: between 0.025 and 250 ng/ml of selenium and arsenic. The present method is applied to determining selenium and arsenic in enviro nmental samples such as surface water, soil, and fish tissue. The sediment standard (MASS-2) and water and tissue sample spike have been tested by the present method with good recoveries. Also, the analytical results for sele nium and arsenic in surface water, sediment, and fish tissue obtained by th e FIA-Hydride-AFS method and Hydride-AAS method are compared. As is clearly shown in these results, the present neu: FIA-Hydride-AFS method not only p rovides good agreement with the values obtained by the ordinary Hydride-AAS method, but the performance of this system suggests that it will be effect ive for the analysis of arsenic and selenium at ultratrace levels. (C) 1999 Texas Department of Health.