Development of dispersive liquid-liquid microextraction methods for the analysis of polar and nonpolar components in liquid samples

Abstract

This study describes a novel sample preparation method for simultaneous identification of 10 phenolic acids from wine using ion pair dispersive liquid-liquid microextraction based on the solidification of a floating organic droplet (IP-DLLME-SFO). For the first time, the ion-pairing technique combined with DLLME-SFO was applied for the detection of phenolic acids. The IP-DLLME-SFO dramatically enhanced the extraction efficiency for very polar phenolic acids, such as gallic acid and protocatechuic acid, which could not be extracted by DLLME-SFO in the absence of an ion-pairing reagent. The effects of the parameters that can affect the extraction efficiency were systematically investigated, including the type and concentration of ion-pairing reagent, type and volume of extraction and dispersive solvents, extraction time, sample pH, and ion strength. And the optimized microextraction conditions yielded high enrichment factors. The combined application of IP-DLLME-SFO and superficially porous particle (SPP) column provided a sensitivity of analysis method, which can separation 10 phenolic acids with similarity chemical structures in 40 min. The method was validated in terms of linearity, sensitivity, precision and recovery. The coefficient of determination (R2) was higher than 0.994 for all calibration curves. The method linearity was constructed in the range of 0.01 – 15 g/mL, and the sensitivity expressed as limit of detection was as low as 10 ng/mL. The intra- and inter-day precisions were below 7.95 % and 9.33 %, respectively. With a simple dilution, the measured absolute recovery values of around 81.5 ~ 109% were obtained for the compounds, indicating that the extraction efficiency was very high. The method that we developed was successfully applied to the analysis of commercial wine samples with no significant matrix effect, revealing different levels of phenolic acids among these products. The result suggest that the combined use of DLLME-SFO and SPP column may be applicable to the analysis of various polar and non-polar compounds in liquid sample with complex matrices.