Quantitative liquid chromatographic determination of disulfide-containing peptide analogues of vasopressin with dual Hg/Au electrochemical detection.

Quantitative methodology was developed for the analysis of disulfide-containing peptide analogues of vasopressin in biologic media. The procedure employs sample clean-up by an ion-exchange solid-phase extraction cartridge, followed by high-performance liquid chromatography with electrochemical detection. The detector is a dual Hg/Au system operated in series in which the disulfide-containing peptides are first reduced at the upstream electrode and then detected as free thiols at the downstream electrode. The assay is linear in the range 2-100 ng/ml (approximately 2-100 pmol/ml) of urine with a lower limit of detection of 1 ng (approximately 1 pmol) on column. The method displayed general utility for a number of structural analogues of vasopressin.