Use of column with modified silica for interfering retention in a FIA spectrophotometric method for direct determination of vitamin C in medicine

A flow injection system using a column packed with silica modified with aminopropyl groups as reactor in the spectrophotometric detection, at 265 nm, was developed for L-ascorbic acid determination. The column packed (2.79 i.d. and 50 mm length) with modified silica (200 mg) was used to eliminate interference by ionic pair formation between amine groups and interfering compounds. An analytical frequency of 30 samples per hour, a detection limit of 2.0x 10(-6) mol l(-1) and a linear response range between 1.0x10(-5) and 1.0x10(-4) mol l(-1) were obtained in optimized conditions. The estimation of relative standard deviation was 1.58 (n=20) for a 5.0x 10(-5) mol l(-1) ascorbic acid solution. The method was applied in medicine samples to determine ascorbic acid and the results were in agreement of the nominal values. (C) 1998 Elsevier Science B.V.