Efficient molecularly imprinted polymer as a pipette-tip solid-phase sorbent for determination of carvedilol enantiomers in human urine

- A rational synthesis of molecularly imprinted polymer showed great potential and high recovery.
- A simple PT-MIP-SPE was developed to extract carvedilol enantiomers from human urine samples.
- Enantioseparation of carvedilol was improved using an immobilized polysaccharide-based chiral stationary phase.
- The method has been applied in a preliminary study of urinary excretion after administration via oral of carvedilol racemate.

In this work, an efficient pipette tip based on molecularly imprinted polymers solid-phase extraction (PT-MIP-SPE) method was developed for carvedilol (CAR) analysis. This compound is available in clinical practice as a racemic mixture, in which (−)-(S)-CAR is a β- and α1-adrenergic antagonist, while (+)-(R)-CAR only acts as an α1-adrenergic antagonist. Enantioseparation of CAR presented satisfactory retention times (5.85 and 14.84 min), acceptable theoretical plates (N = 2048 and 2018) and good resolution (Rs = 9.27). The separation was performed using a Chiralpak® IA column (100 mm × 4.6 mm, 3 μm), a mixture of methanol:ethanol:water (64:15:21, v/v/v) plus 0.3% diethylamine as mobile phase, temperature of 35 °C and flow rate of 1.5 mL min−1. After density functional theory calculations based on prepolymerization complexes, the best protocol for the MIP synthesis was chosen. Then, some parameters that affect the PT-MIP-SPE technique were investigated. After optimization, the best conditions were 300 μL of water as washing solvent, 500 μL of acetonitrile:acetic acid (7:3, v/v) as eluting solvent, 20 mg of MIP, 500 μL of urine sample (pH 12.5) and no addition of NaCl. Recoveries ± relative standard deviation (RSD%) for (+)-(R)-CAR and (−)-(S)-CAR were 101.9 ± 4.8% and 104.6 ± 2.1%, respectively. The method was linear over the concentration range from 20 to 1280 ng mL−1 for each enantiomer, with correlation coefficients larger than 0.99 for both enantiomers. The method was applied successfully in a preliminary study of urinary excretion after administration of CAR racemate to a healthy volunteer.

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