Abstract: A simple flow injection potentiometric (FIP) system, which uses a tubular cobalt electrode, has been developed for phosphorus nutritional evaluation of seeds and grains. Inorganic phosphorus, Pi, is determined using a 1 x 10^-2 mol L-1 potassium phthalate buffer solution adjusted at pH 4. A sensitivity of 47 mV/decade and an operating range from 10 to 1000 mg L-1 (1 x 10^-4-1 x 10^-2 M) of dihydrogen phosphate are obtained. The inositol phosphates amount, which is referred to the organic phosphorus, Porg, is directly determined from extracts using a 1 x 10^-2 mol L-1 Tris-HCl buffer solution adjusted at pH 8. A sensitivity of 127 mV/decade and an operating range of 10^-1000 mg L-1 (2.5 x 10^-4-5 x 10^-3 M) of Porg (expressed as inositol hexakisphosphoric acid monocalcium) are achieved. Some samples of seed and grain are analyzed by an ICP-OES and a spectrophotometric method to compare results to the developed flow system; no significant differences at the 95% confidence level are observed using a paired t test. Other samples such as animal nursing feed, soybean meal, and corn are also analyzed with the proposed FIP system, showing a good correlation to the ICP-OES values. © 2005 American Chemical Society.

Abstract: A methodology to design a flow injection system with optimized performance characteristics was presented based on coupling a descriptive mathematical model to an optimization algorithm. The method was applied to the sequential determination of glucose and glycerol in a flow injection system using the sandwich technique. The axially dispersed plug flow model was coupled with Powell's optimization algorithm to generate a complete set of flow injection configuration, each of them optimized with respect to its objective function (better sensitivity, highest sampling rate, better resolution, etc.). The user selects the configuration which suits the requirements of the particular application.