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ABSTRACT
A simple, miniaturized micropipette tip-based poly(MAA-co-EGDMA) monolith was prepared by in situ polymerization for sensitive micro-extraction of yohimbine in aqueous and plasma samples. Several parameters for monolith preparation were systematically optimized to obtain monolith with better permeability and absorption property. Methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) were selected as monomer and crosslinker and the ratio of MAA and EGDMA was 1:6. Methanol containing 30% dimethyl sulfoxide was selected as porogens. The prepared micropipette tip-based poly (MAA-co-EGDMA) monolith could be easily connected with a syringe infusion pump for loading solutions. Several factors such as washing solvents, flow rate of sampling, sample volume, and pH of sample solutions which affect enrichment efficiency of yohimbine were also evaluated in this work. Under optimized conditions, good enrichment capacity and stability of poly(MAA-co-EGDMA) monolith were obtained. Finally, the prepared micropipette tip-based poly(MAA-co-EGDMA) monolith solid phase micro-extraction combined with high-performance liquid chromatography was also used to analyze yohimbine in plasma samples. The developed method exhibited good sensitivity with limit of detection as low as 0.5 ng/mL, and also showed wide linearity in the range of 1.0–2000 ng/mL with R2 ≥ 0.998, excellent reproducibility with relative standard deviation (RSD) ≤ 2.5%, and good recoveries in the range of 97.9–103.8% of yohimbine in human plasma.
GRAPHICAL ABSTRACT
