Determination of trace phenolic acids in fruit juice samples using multiple monolithic fiber solid-phase microextraction coupled with high-performance liquid chromatography

Abstract

In this work, a simple and sensitive analytical approach that combined multiple monolithic fiber (MMF) solid-phase microextraction with liquid desorption, followed by high-performance liquid chromatography with diode array detection was proposed for the determination of trace levels of phenolic acids (p-hydroxybenzoic acid, syringic acid, p-coumaric acid and ferulic acid) in fruit juice samples. To concentrate targeted analytes and reduce the interference of sample matrices, a multiple monolithic fiber solid-phase microextraction based on a poly(vinylimidazole-co-ethylene dimethacrylate) monolith was used to extract phenolic acids. Several important extraction parameters, including desorption solvent, extraction and desorption time, pH value and ionic strength in the sample matrix were investigated in detail. Under the optimal experimental conditions, the limits of detection were found to be in the range of 0.17–0.57 μg L⁻¹. The linear range was 2.0–200.0 μg L⁻¹ for syringic acid and 1.0–200.0 μg L⁻¹ for other phenolic acids. Satisfactory linearities were achieved for analytes with the correlation coefficients above 0.99. Satisfactory method reproducibility was achieved by evaluating the intra- and inter-day assay variability with relative standard deviations of both of less than 9%. Relative recoveries higher than 70.5% with RSDs in the range of 0.9–9.9% were obtained in the analysis of real juice samples.