Abstract: A flow-through cell is described for use in both flow injection analysis and HPLC. The carrier solution was 0.2 M NH4OH - NH4Cl buffer (pH 9.5) - 0.5% methanol - 0.5 mM CoCl2, and analysis by HPLC was on a column (25 cm x 4.6 mm) of C18 with a mobile phase similar to the carrier, but with 0.5 mM Na trichloroacetate instead of CoCl2; this system could separate several disulfides. The detection cell contained a dropping-Hg working electrode, a Pt auxiliary electrode and SCE. Differential-pulse polarography of four compounds showed that the catalytic (Brdicka) currents occurred at peak potentials from -1.5 to -1.65 V. With use of 10 µL samples, the detection limit in HPLC was 0.1 mM of dithiodiacetic acid.