Application of a cylic polyamine ionophore in phosphate selective electrodes for environmental analysis

The application of macro- and micro-electrodes constructed using the new io nophore were tested in a range of solution compositions reflecting concentr ations found in fresh waters, and containing Cl-, NO3-, SO42-, HCO32-, H4Si O4 and a natural humic acid. The inhibition of the electrode responses to t hese ions was quantified using a mixed-solution method by optimising the ag reement between the measured potentials and predictions from the Nicolsky-E isenman equation. In addition, measurements were made in separate solutions of KCI to enable results to be compared with the literature. Apart from th e results obtained for humic acid, mean selectivity coefficients for 16 mac ro- and 21 micro-electrode experiments are given. The results indicate inhi bition of the electrode response to phosphate for all the anions in the con centration ranges of 0.05-1 mM Cl-, 0.1-1.0 mM NO3-, 0.1-10.0 mM HCO3- and 0.1-1.5 mM SO42-. with high selectivity for HPO42- in the presence of both dissolved silicon and a standard humic acid. This means that the applicatio n of the electrodes to hard waters is impracticable although studies of sof t waters and laboratory studies in controlled conditions, e.g, calcium phos phate precipitation experiments, are feasible.