Essential Oil of Eucalyptus as Modifier of Carbon Paste Electrode for Voltammetric Determination of Lead Ions

Eucalyptus essential oil was used as a modifier for the carbon paste electrode in the analysis of Pb2+ ions in aqueous samples. To give an optimum current peak for Pb2+ solution, 0.1 M HCl as supporting electrolyte and 10% (w/w) of the modifier were used in the study. Accumulation time of 2 min with pH 6 and deposition time and potential of 150 s and –1500 mV, respectively, gave the optimum conditions for the analysis of Pb2+. Furthermore, results showed that the removal of Pb2+ ions for the regeneration of the electrode can be achieved using multiple stripping of the used electrode. A calibration curve on the analyte concentration of up to 20 ppm was established for lead concentration giving a linearity coefficient of 0.9945. The limit of detection and limit of quantization were also investigated and were found to be 0.87 and 2.90 μA ppm–1, respectively. In the actual laboratory sample, the atomic absorption method gave a Pb2+ concentration of 52.38 ± 0.44 ppm, whereas the voltammetric method gave a Pb2+ concentration of 13.85 ± 5.14 ppm. The results of the study have established and ascertained the ability of the eucalyptus’ essential oil to detect Pb2+; however, it was not highly selective toward Pb2+.