Flow injection flame AAS determination of ascorbic acid based on permanganate reduction

An indirect flow injection method for the determination of ascorbic acid in fruit juices is proposed. Permanganate in an acid medium was injected into an ascorbic acid stream which reduced Mn(VII) to Mn(II). The Mn(II) formed was retained online, proportional to the ascorbic acid concentration in th e sample, on a poly(aminophosphonic acid) chelating resin, which is only se lective for this oxidation state. The non-reduced Mn(VII) was determined by flame atomic absorption spectrometry. The proposed method allows the deter mination of ascorbic acid in. the 0.2-34.5 mug/mL range with a relative sta ndard deviation of 2.2%, detection limit of 0.06 mug/mL, and sample through put of 90 samples/h. The results were consistent with those obtained by the reference method (AOAC).