Tungsten sensor for amperometric detection of organic thiols and proteins

An amperometric sensor constructed with a metallic tungsten wire is reported for the indirect detection of organic thiols and proteins. Cysteine added to mercury(II) (40.0μM) buffered in 5.0 mM sodium acetate at pH 4.7 causes a decrease in the reduction current of mercury at −0.2 V (vs. SCE). Detection limits were found to be in the range 0.05–0.2 μg/mL for cysteine, thiourea and glutathione, but were poorer for albumin and DNA, showing this method is relatively selective for cysteine. The advantages of the tungsten electrode are its low cost, miniature size, and its inert oxide surface which does not amalgamate with mercury.