A New Molybdate-selective electrode based on Higher quaternary Ammonium Salts

Membrane composition of molybdate-selective electrodes based on higher quaternary ammonium salts has been optimized. It is found that the best analytical characteristics of electrodes are based on 3,4,5-tris-dodecyloxybenzyl) tetraoxyethyltrimethyl ammonium in chloride form (5% w/w) with the addition in membranes of the solvating additive (neutral carrier) − p-heptyl ester 4-trifluoroacetylbenzoic acid (TFABAHE, 20% w/w). Their analytical characteristics: low detection limits (1·10−6mol/l); logarithm selectivity coefficients relative to interfering chloride -1,-4, sulfate -0.8, bromide -0.7, tungstate -0.9 ions; working range of pH (8.5−9.5); slope of the electrode function (24.4 mV/decade) are determined. Sodium molybdate aqueous solutions has been studied with FT-IR spectrometry method at various pH. In sodium molybdate solutions at pH greater than 8.0‒8.5 hydrolytic processes are mild. However, using a molybdate-selective electrodes is better to use freshly prepared solutions. This increases the reproducibility of the experimental results. The proposed electrode was employed to determine of molybdate ions of model water samples using the calibration plot method.