MICROPOROUS GOLD ELECTRODES AS COMBINED BIOSENSOR ELECTROCHEMICAL DETECTORS IN FLOWING STREAMS

Microporous gold electrodes are described for us? as flow-through bios ensor/electrochemical detectors in both flow injection analysis (FIA) as well as postcolumn detection in HPLC. Electrodes prepared by the co valent immobilization of tyrosinase onto the electrode surface (via a chemisorbed layer of thioctic acid and poly-lysine) are used to demons trate the utility of the electrode. Such electrodes are shown to respo nd to a variety of substituted phenols under FIA conditions at applied potential of only -50mV (vs. Ag/AgCl). Detection limits of 0.5 mu M c atechol and 3.4 mu M phenol were achieved with a sample throughput rat e of 38 samples/h. The electrode is shown to be stable for up to 14 da ys of use. The porous bioelectrode is shown to be useful as a postcolu mn detector for substituted phenols following their separation by HPLC . Various techniques for immobilization of the enzyme onto the electro de surface (covalent and noncovalent) as well as factors affecting sen sitivity and through-put (buffer ionic strength and addition of organi c modifier) an discussed.