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

• A new phosphate-selective poly[vinylchloride-co-vinylacetate-co-vinylalcohol] membrane with carriers based on tin compound were proposed hydrophilic target anion.
• Membranes with low dielectric plasticizers exhibit a remarkable selectivity responses to the highly hydrophilic anion phosphate over interfering anions.
• The response time and selectivity of the membrane with copolymer are close to the required values.
• The lifetime of the poly[vinylchloride-co-vinylacetate-co-vinylalcohol]-based-membrane was higher than that of PVC-based-membrane.
• Sensors can be stored in phosphate-containing environments and proposed for phosphate selective detection.

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 × 10−08 M with a linear response towards phosphate ion over a wide concentration range of 10−5–10−3 M. 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 20 s and 40 s, when changing from 10−4 M phosphate to 10−3 M. 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.