Fabrication and Characterization of Molecularly Imprinted Microspheres as Highly Effective Sorbent for Fast and Selective Solid Phase Extraction of Nicotinamide in Beef and Wheat Flour Samples

Vitamin B3 (Nicotinamide) is involved in many vital reactions in the human body as the precursor of NAD and NADP. NAM deficiency can lead to pellagra thus foods are fortified with this vitamin. On the other hand, high intakes of NAM can cause some symptoms.  Hence, a cheap, rapid, selective and sensitive determination of NAM concentration in foods is crucial. The present study propose a NAM analysis method for beef and wheat flour by employing a molecularly imprinted polymer based solid phase extraction clean-up coupled with HPLC-UV. Precipitating polymerization technique for fabrication of NAM molecularly imprinted microspheres was utilized. The effects of polymer ingredients including functional monomer, cross-linker monomers, template and solvent were investigated on binding characteristics.The binding behaviour of the polymer well modeled through Freundlich equation and the polymer showed high selectivity of NAM over nicotinic acid (NA). In a kinetic study, 79% of NAM binding and 96.5% of NAM release occurred immediately. The NAM imprinted microspheres were packed into SPE for NAM extraction, food samples injected and the output analysed with HPLC-UV. Good linearity was obtained for solid phase extraction of NAM in the range 148–5000 μg L-1 (R2 = 0.999) and high extraction recoveries of 77–102% and 81–87% were obtained for NAM in beef and wheat flour samples, respectively. The limit of detection (LOD) and limit of quantification (LOQ) for nicotinamide  were 44 μg L-1 and 148 μg L-1, respectively. The overall inter-day and intra-day relative standard deviations of  2.13% to 5.31% for wheat flour (n=4), and 1.89% to 5.22% for beef samples were obtained, demonstrating good precision of the proposed method in its application for real sample analysis.