Determination of retinoids in human serum, tocopherol and retinyl acetate in pharmaceuticals by RP-LC with electrochemical detection.

A liquid chromatography with a electrochemical detector method has been developed of the quantitative measurement for the three retinoids in human serum (13-cis and all-trans retinoic acid and retinol), as well as tocopherol acetate, retinyl acetate and retinol in pharmaceuticals. The detection cell consisted of a glassy carbon electrode held at 1.0 V versus an Ag/AgCl reference electrode. The maximum electrochemical signal was obtained with a supporting electrolyte containing 92% methanol 0.1 M acetate buffer (pH 4.72) as the mobile phase. The quantification limits are 0.5, 0.2, 0.4, 0.5, 0.8 and 0.8 ng for tocopherol acetate, all-trans-RA, 13-cis-RA, retinol, retinal and retinyl acetate, respectively. The electrooxidation process is applied for the simultaneous quantitative determination of retinoids in human serum. Comparison with results obtained from HPLC-UV shows agreement.