Determination of Lead in Some Environmental Samples Using Chemically Modified Carbon Paste Electrode Based on Lead Tetrakis(lmidazolyl)Borate

摘要

Potentiometric chemically modified carbon paste electrode (CMCPE) that is highly selective to Pb(ll) ions was prepared by using lead tetrakis(imidazolyl)borate (PbTImB) as a suitable ion-exchanger. The best electrode performance was obtained with a paste composition of 7.0% PbTImB, 49.5% dioctyl adipate as solvent mediator, and 1.0% PbSO_4 as additive. The electrode displays an excellent Nernstian response (29.89 mV/concentration decade), wide concentration range of 1.60 × 10~(-6) - 1.00 × 10~(-2) mol L~(-1) and a detection limit of 1.30 × 10~(-6) mol L~(-1). The electrode is suitable for use in a wide pH range of 5.8-8.8 and it has a rapid response time of 14 s over the entire concentration range (1.00 × 10~(-5) - 1.00 × 10~(-1) mol L~(-1)). The selectivity behavior of the proposed sensor shows substantial improvements in comparison to many previously reported electrodes for lead ion. Except for copper, and cadmium cations, the electrode exhibits good selectivity over a number of alkali, alkaline earth, transition and heavy metal ions. The paste sensor can be used for at least 3 months without any divergence in potential. The electrode was used as an indicator electrode for the potentiometric titration of lead solutions with EDTA or K_2CrO_4, and successfully applied to the determination of lead ions in drinking water and air samples.