Separation and detection of bis(alkylthio)selenides of penicillamine and glutathione by liquid chromatography with electrochemical detection.

Sensitive and selective methodology is described for the simultaneous determination of thiols, disulfides and bis(alkylthio)selenides in mixtures formed by reaction of selenious acid with thiols. The methods are based on separation of the various compounds by reversed-phase ion pairing chromatography followed by detection with an electrochemical detector equipped with dual mercury/gold amalgam electrodes in series in the eluent stream. Thiols are detected directly at the downstream electrode. Bis(alkylthio)selenides and disulfides are detected indirectly by first reducing them at the upstream electrode followed by detection of the reduction products at the downstream electrode. Bis(alkylthio)selenides are reduced at less negative potentials than disulfides, making it possible to selectively detect them in mixtures with disulfides. Detector response to bis(penicillamine)selenides is linear from 1.1.10(-7) M up to at least 1.2.10(-4) M; the detection limit is estimated to be less than 2 pmol bis(penicillamine)selenide.