Magnetic solid phase extraction based on restricted access molecularly imprinted polymer with dually coated for enantioselective determination of tramadol in human plasma by capillary electrophoresis with ultraviolet detection.

A restricted-access magnetic molecularly imprinted polymer with dually coated of hydrophilic monomer and bovine serum albumin was synthesized, properly characterized by different techniques, and used as adsorbent in Magnetic Solid Phase Extraction (MSPE). Furthermore, a simple and efficient method employing capillary electrophoresis with ultraviolet detection was developed and validated for the enantioselective determination of tramadol (TRM) in human plasma. The optimized conditions were 25 mM phosphate background electrolyte at pH 9.05 using 0.01 g of sulfated-β-cyclodextrin as chiral selector, hydrodynamic injection at 40 mbar for 4 s, voltage at 10 kV, temperature of 25 °C, and a fused silica capillary with an effective length of 50 cm. In these conditions, (-)-(1S,2S)-TRM exhibited a migration time of 8.48 min and (+)-(1R,2R)-TRM of 9.50 min. Several factors affecting the MSPE were optimized, achieving extraction recoveries/relative standard deviation of 99.6 ± 8.1 % by means of 100 μL of human plasma at pH 8, 1000 μL of acetonitrile as eluent, 20 mg of adsorbent, 200 μL ultrapure water as washing solvent, and 60 s of stirring. The method was linear (range of 100-3000 ng mL⁻), selective, and accurate, with a limit of quantification and detection of 100 and 50 ng mL⁻, respectively, for both enantiomers, allowing their determination in real human plasma samples. This method presents an important alternative for monitoring athletes and in forensic applications.