Highly Selective and Sensitive Asymmetric Lead Microsensor Based on 5,5,dithiobis(2-nitrobenzoic acid) as an Excellent Hydrophobic Neutral Carrier for Nano Level Monitoring of Lead in Real Samples

Solution investigations between 5,5,dithiobis(2-nitrobenzoic acid) (DTBA) and a number of alkali, alkaline earth, transition and heavy metal ions showed a strong tendency of DTBA for lead ions. Then, it was evaluated as neutral ionophore in construction of an asymmetric lead microsensor. The proposed lead microsensor with a membrane composition containing 18% poly(vinyl chloride) (PVC), 74% dibuthyl phthalate (DBP) as solvent mediator, 3% potassium tetrakis(p-chlorophenyl) borate (KTpClPB) as an anionic additive, and 5% DTBA as an ionophore. The microsensor exhibits a nice Nernstian response of 29.1 +/- 0.4 mV per decade of lead activity, and a wide dynamic working range 1.0 x 10(-3)-1.0 x 10(-9) M. The detection limit of the sensor is 6.0 x 10(-10) M and can be used in the pH range of 3.5-9.0. The microsensor has fast response time, and relatively long life time (more than 12 weeks). It was applied for the determination of lead ion contents in water, black tea, hot and black pepper samples.