Novel phosphate-selective poly(vinyl chloride-co-vinyl acetate-co-vinyl alcohol) membrane optode with carrier based on tin compound

Abstract

A new phosphate-selective poly[vinylchloride-co-vinylacetate-co-vinylalcohol] membrane with Trioctyl-tin-chloride (Carrier I) and Methylenebis[dibromo(phenyl)stannane] (carrier II) were proposed to invert the Hofmeister behaviour and to form strong complexes with the hydrophilic target anion. Plasticizers effect and selectivities for phosphate over many common anions, such as nitrate, chloride, fluoride and bicarbonate, at pH 3.6 are studied for several membranes formulations. We show that the phosphate selectivity is better and comparable to required values for membranes based on tin compound plasticized with low dielectric constant solvent and the sensor exhibits a LOD of about 6.5×10−08M with a linear response towards phosphate ion over a wide concentration range of 10−5–10−3M. The response times and lifetime of copolymer-membranes-optodes were studied. The response times of the membranes with copolymer based on carriers I and II were 20s and 40s, when changing from 10−4M phosphate to 10−3M. The lifetime of the copolymer-based-membrane was higher than that of PVC-based-membrane with the same carrier and the optode is adequate for phosphate ion detection in real water.