Selective and sensitive voltammetric determination of folic acid using graphite/restricted access molecularly imprinted poly(methacrylic acid)/SiO 2 composite

The present study demonstrates the development of a voltammetric sensor based on graphite/restricted access molecularly imprinted poly(methacrylic acid)/SiO2 composite for folic acid determination in pharmaceutical formulation. The insertion of hybrid molecularly imprinted polymer with restricted access (RAM-MIP) into the graphite paste provided enhance in the cathodic peak current for FA. As the electric conductivity of RAM-MIP is very poor, the optimum content was found to be very low (3%, w/w) in the composite. Under optimized conditions (0.1 mol L−1 Britton-Robinson buffer and pH 4.5) using square wave voltammetry (frequency of 150 Hz, pulse amplitude of 90 mV and potential increment of 7 mV) a limit of detection of 0.72 μg L−1 (1.63 nmol L−1) and a linear range from 5.0 to 100.0 μg L−1 (0.01 to 0.23 μmol L−1) were obtained. The method precision was assessed in terms of inter-day (n = 6) and intra-day precision (two consecutive days), whose relative standard deviations (RSD%) ranged from 3.56 to 5.01%. The developed method was applied for FA determination in pharmaceutical samples whose accuracy was attested by means of addition and recovery assays (97.7–105.0%) as well as by high performance liquid chromatography (HPLC) as a reference technique, thus indicating that RAM-MIP sensor might be successfully applied for quality control in the real samples.