Optimization of electrochemical hydride generation in a miniaturized electrolytic flow cell coupled to microwave-induced plasma atomic emission spectrometry for the determination of selenium

The optimization of a continuous flow system for electrochemical hydride ge neration coupled to microwave-induced plasma atomic emission spectrometry ( MIP-AF-S) for the determination of Se is presented. A small electrolytic ce ll with a porous glassy carbon working electrode was used for hydride gener ation. When using an Ar MIP operated in a TE101 cavity a detection limit of 0.6 ng mL(-1) (3 sigma) could be achieved. The calibration curve was linea r up to 1 mug mL-1. A standard deviation of less than 2% (10 replicate anal yses) could be achieved. It was shown that interferences of transition meta ls are of the same order of magnitude as with a larger electrolysis cell de scribed earlier, and light elements hardly caused any signal depression as tested. It was possible to distinguish between Se(IV) and Se(VI) species an d seleno-DL-methionine, because under optimized conditions of an electrolys is current of 10 mA, a microwave power of 210 W, an Ar flow rate of 15 L h( -1) and a sample flow rate of 2.5 mL min(-1) only Se(IV) was transformed to H2Se and transferred into the plasma. Finally, the possibility of an elect rochemical pre-enrichment was shown to enable it to further decrease the de tection limit.