Tetraheptylammonium hydrogen phthalate membrane electrodes for the determination of plasticiser in poly(vinyl chloride)

Abstract

Hydrogen phthalate-selective poly(vinyl chloride)(PVC) matrix and liquid membrane electrodes have been developed for the indirect determination of total phthalate in PVC. The PVC matrix membrane electrode exhibits a Nernstian response in the range 10^–1–4 × 10^–4M hydrogen phthalate with a slope of 59 mV per concentration decade. The electrode has a narrow working pH range (3.4–4.2), a fast response time (less than 5 s) and high selectivity for hydrogen phthalate in the presence of many organic acids. For the determination of phthalate in PVC, the extracted plasticiser is first hydrolysed to phthalic acid and then measured by the PVC matrix membrane electrode at pH 4. The determination of phthalate in some commercial PVC samples gave results that were in good agreement with those obtained by a standard titrimetric method.