Evaluation of poly(vinylpyridine)-supported protoporphyrin resin for the sampling/separation of manganese(ii) using a hyphenated FIA-FAAS system

Abstract

The present study describes the development of a preconcentration method for manganese determination by FAAS using poly(protoporphyrin-co-vinylpyridine) as a sorbent. To synthesize this material, 4-vinylpyridine and protoporphyrin were copolymerized in the presence of ethylene glycol dimethacrylate as a cross-linker and 2,2-azobisisobutyronitrile as an initiator. The factors affecting the flow injection preconcentration system were optimized by employing 2⁵ fractional factorial and Doehlert matrix designs. The proposed on-line preconcentration method was performed by percolating 18.0 mL aliquots of Mn(II) solutions (pH 8.3) at a flow rate of 6.0 mL min⁻¹ through a mini-column, packed with 100 mg of poly(protoporphyrin-co-vinylpyridine); the Mn(II) ions were then on-line eluted with 1.5 mol L⁻¹ HNO₃ into the FAAS nebulizer. Under these conditions, it was possible to yield a linear curve in the concentration range of 0.0–120.0 μg L⁻¹, with a correlation coefficient of 0.997. Besides, the following system parameters were obtained: sampling frequency of 15 h⁻¹, preconcentration factor of 53, consumptive index of 0.34 mL, concentration efficiency of 17.6 min⁻¹, detection limit of 0.34 μg L⁻¹, and quantification limit of 1.13 μg L⁻¹. The method precision (repeatability) estimated for ten measurements of 1.0 and 50.0 μg L⁻¹ Mn(II) standard solutions was found to be 5.2 and 4.9%, respectively. Moreover, the protoporphyrin incorporation into the poly(vinylpyridine) network caused a remarkable 323% increase in the method's sensitivity. Finally, the proposed procedure was not affected by potentially interfering ions. Thus, it was successfully applied to the Mn(II) determination in water, food and sediment samples.