―Determination of some heavy metals in polyethylene terephthalate (PET) bottles of drinking water available in local market of Ambo town Oromia, Ethiopia

Abstract

Heavy metals are natural constituents of the Earth's crust. Owing to their persistence, high toxicity and the tendency to accumulate in the ecosystem, heavy metals pose a threat to human health. The aim of this study is to evaluate the content of heavy metals in Polyethylene terephthalate (PET) made drinking water bottles. The bottle samples were purchased from Ambo town markets. The PET packaging samples were digested on Kjeldahl digestion apparatus (Gallenkamp, Englandon) and the metals were analyzed by using Flame Atomic Absorption Spectrophotometer (FAAS) analyzer, Agilent technologies Model 200 series AA. In this study, various digestion procedures were tested and the procedure that produced a colorless solution and consumed the shortest digestion time was chosen as the working procedure. The optimum acid volume ratio in the digestion mixture found was 4:3:1 for HNO3, HClO4 and H2O2 respectively, the digestion time of 2:50 hr and digestion temperature of 230 °C were found to be the best conditions for the digestion of 1 g of powdered and homogenized PET samples. The mean concentration levels of heavy metals such as Cu, Zn, Ni, Cr and Co, were detected and quantified within the range of 4.12 ± 0.01 - 110 ± 1, 19.36 ± 0.74 - 114 ± 5.75, ND - 78.48 ± 0.1, 5.06 ± 0.01 - 18.4 ± 0.01 and ND - 14.3 ± 0.01 mg/kg respectively, and the concentration levels of Mn, Cd and Pb were not detected (ND) in all the tested plastic samples. The recovery study for heavy metals in PET bottle brands were in the range of 95.85 - 106.67%, which is within acceptable range for the routine analysis. The precision was checked in terms of relative standard deviation (<5.16%) indicating good precision of the method for heavy metal analysis in PET bottle samples.