Abstract:

In the present study, we developed a vortex-assisted switchable solvent liquid-phase microextraction (VA-SSLPME) approach to extract four cinnamic acid derivatives in traditional Chinese medicinal samples prior to HPLC analysis. During the extraction process, hypotoxic hexanoic acid was used as a switchable polarity extraction solvent. First, hydrophobic hexanoic acid was converted into a hydrophilic form by the addition of sodium carbonate. Then, sulfuric acid was added to lower the pH value of the mixture, which induced the retransition of hexanoate ion into hexanoic acid, generating carbon dioxide (CO₂) bubbles in situ. The formation of CO₂ bubbles further facilitated the rise of hexanoic acid and expedited the separation of the organic phase from the aqueous phase. Herein, the critical parameters that affect the enrichment factor were optimized, including the type and amount of extractant, the volume of sodium carbonate solution, ionic strength, mineral acid type, and extraction time. Under the optimized conditions, enrichment factors of target analytes were 7–57 with satisfactory accuracies and precision. The limits of detection and quantitation were 2.0–7.0 and 5.0–15 ng/mL, respectively. In the present work, we successfully applied the proposed method for the simultaneous extraction, enrichment, and determination of four cinnamic acid derivatives in traditional Chinese medicinal samples.

Key words: Switchable solvent, VA-SSLPME, Traditional Chinese medicine, Cinnamic acid derivatives