Abstract
A novel flow injection (FI) system is presented for simple, rapid and sensitive determination of hexacyanoferrate (II)(ferrocyanide) at ppm to sub-ppm levels in salts. The anion exchange column incorporated in-line in a flow injection system was utilized as an integrated field for both the separation/preconcentration of ferrocyanide from a large excess of NaCI matrix and coexisting other elements, and the detection reaction of adsorbed ferrocyanide with Fe (III) complex with 1, 10-phenanthrolin (ferrin). Ferrocyanide adsorbed on the column directly reacts with ferrin, which was introduced into the column by switching its flow, and detected spectrophotometrically by measuring the resultant ferroin at 512 nm. Ferriin is prepared in-line by passing the ferroin solution through an MnO2 solid reactor in the flow system, providing the advantage that unnecessary lowering of sensitivity due to dilution and additional reagent stream line were avoided. The variables relating to such reactions and minifold were studied in detail and the optimal conditions and manifold configurations were established. A linear calibration using a 6 m sample loop injection was obtained for ferrocyanide in the range of 0-0.3 ppm (in the presence of 0.5 mol/L NaCl matrix). The coefficient of variation for 0.05 ppm ferrocyanide was 1.6% (n=3), and the estimated limit of determination was 0.003 ppm. Only 9 min was required for analytical measurement after sample injection and no complicated manual operation was needed. The present FI system was successfully applied to determine ferrocyanide at ppm level in the real salt samples with satisfactory precision of less than 3%.
