Synthesis And Performance Of Cross-Linked Poly (Vinylpyridine-Co-Protoporphyrin) For Effective Cobalt Determination Using A Micro-Packed Column Hyphenated System Coupled To Faas

The present study describes the development of a solid phase preconcentration method for cobalt determination at trace levels using cross-linked poly(vinylpyridine-co-protoporphyrin) as a highly efficient adsorbent and a hyphenated flow injection-FAAS system. The influence of molar amount of protoporphyrin and 4-vinylpyridine in the copolymer was studied aiming at obtaining the optimum synthesis condition in terms of adsorption capacity and swelling effect. The polymers were characterized by FT-IR, SEM, nitrogen adsorption/desorption, and swelling analyses. The method is based on cobalt preconcentration at pH 9.0 in 0.01 mol L-1 Tris/Tris-HCl buffer through the cylindrical mini-column packed with 50 mg of adsorbent at a flow rate of 7.4 mL min-1, whilst the elution was carried out by using 2.0 mol L-1 HNO3. Using the best synthesis conditions, the solid phase preconcentration method using poly(vinylpyridine-co-protoporphyrin) named poly(4VP-PP) (5.00 mmol of 4-vinylpyridine and 0.10 mmol of protoporphyrin) provided a linear range from 4.60-200.0 mu g L-1, the limit of detection of 1.38 mu g L-1, preconcentration factor of 38, consumption of index of 0.53 mL and analytical frequency of 22 h-1. Using the poly(4VP-PP), the method showed high selectivity for cobalt determination in the presence of concomitant ions, when compared to poly(4VP), thereby indicanting the great importance of protoporphyrin on the selective analytical performance of the method. The poly(4VP-PP) was successfully applied for the preconcentration of cobalt from different kind of samples without matrix interference, including dark chocolate powder, black tea, infusion of black tea, and water samples (mineral, tap, and lake waters), with high recovery results (91-104%). The feasibility of the method was also attested by analysis of certified reference material of marine sediment (MESS-3).