Determination of Pb+2 ions in environmental samples using graphite electrode modified with liquid membrane based on molecularly imprintedpolymer

Molecular imprinting is a useful technique for the preparation of functional materials with molecular recognition properties. The molecular imprinting technique is a powerful method forpreparing artificial recognition sites with predetermined selectivity for a wide range of target molecules. Molecular imprinted polymers (MIPs) are being extensively used as synthetic polymer-based receptors or as artificial antibodies, because of their ability to mimic naturalsystems. However, when compared to natural recognition products, they offer several advantages such as robustness, specificity, reusability and cost-effectiveness. They also exhibit resistance to extreme conditions, like high temperature, acidic and basic environments, and therefore lendthemselves to engineering possibilities compared with biological counterparts. Lead is one of the most toxic chemicals that pose a wide range of dangers to human's health. In addition to renal disease, cardiovascular effects and reproductive toxicity may cause irreversibleneurologic damage. As described elsewhere, continuous exposure with lead may cause adverse and poisonous effects to the brain, blood, kidneys, nervous and reproductive system along with other diseases. Therefore, it is desired to develop the simple, selective, sensitive, efficient andeco-friendly methods for the determination of trace levels of Pb2+ ions in environmental and biological samples. In recent years, various instrumental techniques including; spectrophotometric methods, atomic absorption and emission spectroscopy and mass spectrometry have been applied to the determination of Pb2+. However, most of these techniques are either time consuming, involving multiple sample manipulations, or too expensive for mostanalytical laboratories. A membrane electrode based on molecularly imprinted polymer were designed and prepared. The best response characteristics were obtained using the composition: 5% molecularly imprinted polymer as ionophore, 63% dibutyl phthalate as plasticizer and 30% polyvinyl chloride. The sensor exhibits a Nernstian response for lead ions over a wide concentration rangeof 1.0×10−2 to 1.0×10−6M with a slope of 29.3 ±0.1 mV/decade of activity. It has a fast response time of about 20 s and can be used for at least five weeks without any divergence inpotential. The electrode can be used in the pH range4.0–8.0The proposed sensor shows fairly good discriminating ability towards lead ions in comparison with some alkali, alkaline earth, transition and heavy metal ions. At the end of the electrode performance by using analytical measurement of Pb2 + ion in real samples of well water, municipal and industrial waste water by using a calibration graph was demonstrated.

Keywords:

Ion-selective electrode , Membrane PVC , Lead (II) , Moleculary imprinted polymer , Polyvinyl chloride