Synthesis of Pb( ii )-imprinted poly(methacrylic acid) polymeric particles loaded with 1-(2-pyridylazo)-2-naphthol (PAN) for micro-solid phase preconcentration of Pb 2+ on-line coupled to flame atomic absorption spectrometry

In the present study, a new ion-selective imprinted polymer based on poly(methacrylic acid) loaded with 1-(2-pyridylazo)-2-naphthol (PAN) (IIP/PAN) has been synthesized, characterized and evaluated as a solid adsorbent for the preconcentration of Pb 2+ with on-line determination by Flame Atomic Absorption Spectrometry (FAAS). For comparative study, a blank polymer (NIP) and IIP (imprinted polymer) without PAN were synthesized. The polymers were characterized by FT-IR and textural data through nitrogen adsorption/desorption measurements. Selectivity studies were performed by comparing the competitive adsorption of Pb 2+ with Cu 2+ , Cd 2+ , Ni 2+ , Co 2+ and Zn 2+ on IIPs and NIP, yielding relative selectivity coefficients ( k ′) higher for IIP/PAN than for IIP and NIP, which confirms the effect of PAN on the improvement of selective performance of IIP. Adsorption kinetic studies showed that the equilibrium adsorption of Pb 2+ was reached at 100 min for the three polymers and its data were well described by pseudo-second-order and Elovich models. The maximum adsorption capacities (MAC) were found to be 41.4 mg g −1 for IIP/PAN, 34.2 mg g −1 for IIP and 30.1 mg g −1 for NIP. The proposed on-line preconcentration method was based on loading 20.0 mL of Pb( ii ) solution (pH 5.70 buffered with 0.048 mol L −1 acetate buffer) through 30 mg of IIP/PAN packed into a minicolumn at 4.0 mL min −1 flow rate with further elution using 1.0 mol L −1 HCl solution. The limits of detection (LOD) and quantification (LOQ) were found to be 0.52 and 1.79 μg L −1 , respectively, and linearity was from 1.75 to 200.0 μg L −1 ( r = 0.989). The precision of the method assessed in terms of repeatability was found to be 4.1 and 1.9% for 10.0 and 150.0 μg L −1 Pb( ii ) solutions, respectively. The developed method was successfully applied to different kinds of samples (water, synthetic seawater, serum physiological solution, chocolate powder and Gingko biloba ) and its accuracy was assessed by means of recovery tests and analysis of a certified reference material (MESS-3, marine sediment).