Potentiometric Differentiation of Mono- and Macromolecular Thiol within Human Plasma at Carbon Fiber Electrodes

The potentiometric responses of mono- and macromolecular thiol species derivatized with a naphthoquinone indicator have been assessed at electrode designs based on laminated carbon fiber assemblies. The nature of the response for each type of species was found to depend strongly on the electrode geometry and composition and can be used to discriminate between the different thiol moieties. The efficacy of the electrode systems for the measurement of plasma thiols within normal and diabetic blood samples has been assessed, and a possible mechanism for the differing responses has been proposed.