Selectivity in flow injection analysis

Abstract A generalized method for assessing the extent of interference of foreign species on a given chemical assay is proposed. The interference can be quantified by a parameter termed selectivity coefficient. The method is based on injecting the analyte and the interfering species simultaneuosly, and then letting them merge eithe synchronously or asynchromously; the analytical readout is taken from the element of fluid where the dispersion of the two species is identical. It is shown that this makes the accompanying calculations simple, because the selectivity coefficient can be related directly to the originally injected concentrations. The general method is demonstrated for a spectrophotometric procedure for the determination of manganese with formaldoxime, and the selectivity coefficients for various metal ion are determined. The applicability of three different f.i.a. manifold configurations is discussed.