Determination of lead, cadmium, zinc and tin in samples of poly(vinyl chloride) by square-wave voltammetry and atomic absorption spectrometry

Abstract

Many metallic compounds used as stabilizers are incorporated in poly(vinyl chloride)(PVC) to improve its characteristics for various commercial applications. The determination of Pb, Cd, Zn and Sn in PVC samples by square-wave voltammetry (SWV) and atomic absorption spectrometry (AAS) is described. Two different procedures, using H₂SO₄—H₂O₂—NH₃—ethylenediaminetetraacetic acid and H₂SO₄—H₂O₂—HNO₃ reagents to dissolve lead sulfate, were developed in order to suit the experimental requirements of AAS and SWV methods. The Pb—Cd—Zn mixed metal system was analysed by SWV and AAS and good recoveries were found for synthetic samples. The advantage of SWV over AAS is that it is more sensitive and the simultaneous determination of these elements is feasible. A good correlation between the data from SWV and AAS was obtained for all the metals (r>0.995). Tin can be readily determined using SWV and AAS methods. The SWV determination of Sn using 1 mol dm^–3 HCl—4 mol dm^–3 NH₄Cl buffer was carried out and the recovery was comparable to that obtained using AAS. The same method was extended to a commercial sample. Statistical evaluation showed no significant bias between the methods used.