Restricted access polypyrrole employed in pipette-tip solid-phase extraction for determination of nimodipine and nicardipine in breast milk

A HPLC-UV method for the determination of nimodipine and nicardipine in breast milk using restricted access polypyrrole as an adsorbent in pipette-tip solid-phase extraction (PT-SPE) has been developed. The chromatographic conditions were a C-18 column (150 mm x 4.60 mm, 5 mu m) using methanol : acetonitrile : ultrapure water (55 : 30 : 15, v/v/v) at a flow rate of 1.0 mL min(-1) and detection at 236 nm. The adsorbents have been synthesized and characterized by using Fourier-transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, surface analysis, wettability and point zero charge, and were then applied in sample preparation. The main parameters that affect analyte recovery from breast milk by PT-SPE were optimized and the analytical method showed recoveries around 100%, linearity from 3 to 3000 ng mL(-1), and correlation coefficients (r) = 0.99 for the two analytes, in addition to adequate precision, accuracy and robustness. Finally, the validated method has been successfully applied in analyses of breast milk from volunteers.