Rapid determination of folic acid and riboflavin in urine by polypyrrole magnetic solid-phase extractant combined ultra-performance liquid chromatography.

Determination of folic acid and riboflavin in biological samples is difficult due to their high polarity, low concentration, chemical instability, and complex matrix. In this study, the polypyrrole-coated magnetic nanocomposite (Fe3O4@PPy) was synthesized innovatively with the assistance of hexadecyltrimethylammonium bromide. To evaluate the adsorption mechanism and the feasibility of synthesized Fe3O4@PPy as an adsorbent, the adsorption capacities, kinetics and thermodynamics of folic acid and riboflavin were investigated systemically. Furthermore, in light of the chemical instability of folic acid and riboflavin a method for rapid extraction and detection of them from human urine within 10 min was developed successfully by combining magnetic solid phase extraction with ultra-performance liquid chromatography (MSPE/UPLC). The adsorption parameters including sorbent amount, pH value, extraction time, desorption solvent and desorption time were studied. Under optimum conditions, the performance of the established determination method was validated with the linearly dependent coefficients (>0.9995), the limits of detection (0.02-0.05 µg/mL), the limits of quantification (0.07-0.18 µg/mL), and the recoveries (92.2-105.1%, with relative standard deviation < 3.3%). The rapid extraction and detection of folic acid and riboflavin from real urine samples were achieved subsequently. The present study suggests that the developed method exhibits a promising application in the analysis of free folic acid and riboflavin in human urine samples, which can provide a reference for the clinical drug monitoring and treatment.