Flow-Injection Determination of Retinol and Tocopherol in Pharmaceuticals with Acidic Potassium Permanganate Chemiluminescence

Abstract

A simple and rapid flow-injection method is reported for the determination of retinol, its derivatives and α-tocopherol by its enhancement effect on a potassium permanganate-formaldehyde chemiluminescence system in an acidic medium. Linear calibration graphs were obtained between 5.0 × 10^-8 to 5.0 × 10^-6 mol L^-1 for all-trans-retinol, 5.0 × 10.8 - 2.5 × 10^-6 mol L^-1 for all-trans-retinal, 5.0 × 10^-7 - 1.0 × 10.5 mol L^-1 for retinoic acid, 1.0 × 10^-7 - 5.0 × 10^-6 mol L^-1 for retinyl acetate and retinyl palmitate and 1.0 × 10^-8 - 5.0 × 10^-6 for α-tocopherol, with relative standard deviations (RSD; n = 4) in the range of 0.8 - 2.8%. The limits of detection (S/N = 3) were in the range of 5.0 × 10^-9 - 1.0 × 10^-7 mol L^-1 with a sample throughput of 100 h^-1. The influence of common ions, excipients in pharmaceutical preparations and related organic compounds were studied on the determination of retinol and α-tocopherol individually. The method was applied to determine retinol and α-tocopherol in pharmaceutical preparations, and the results obtained were in reasonable agreement with the amount labelled.