A ¯ow injection system using a column packed with silica modi®ed 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 modi®ed 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 2.010ÿ6 mol lÿ1 and a linear
response range between 1.010ÿ5 and 1.010ÿ4 mol lÿ1 were obtained in optimized conditions. The estimation of relative
standard deviation was 1.5% (n20) for a 5.010ÿ5 mol lÿ1 ascorbic acid solution. The method was applied in medicine
samples to determine ascorbic acid and the results were in agreement of the nominal values. #