Simple and Sensitive Determination of Aromatic Acids in Coconut Water by g-C3N4@SiO2 Based Solid-phase Extraction and HPLC-UV Analysis

In this study, graphitic carbon nitride deposited silica(g-C3N4@SiO2) was prepared by simple pyrolysis of melamine on silica and then used as a solid-phase extraction(SPE) sorbent for the extraction of four representative aromatic acids including benzoic acid(BA), salicylic acid(SA), indolyl-3-butyricacid(IBA) and naphthalene acetic acid(NAA) in coconut water(CW) samples. g-C3N4@SiO2 exhibited an excellent adsorption capacity for the four aromatic acids, which are in the concentration range of 500–558.8 μg/g. The four aromatic acids could be directly captured by g-C3N4@SiO2 from CW samples within 5 min. Thus, a rapid, simple and effective method for the analysis of four aromatic acids in CW samples was developed by coupling g-C3N4@SiO2-based SPE with high performance liquid chromatography-ultraviolet(HPLC-UV) detection. The linearity of the developed method was in the range of 20–1000 ng/mL and its limit of detection was in the range of 1.9–5.7 ng/mL, which were significantly lower than those of the reported similar methods. The intraday and interday precisions(based on the relative standard deviation, n=3) of the four aromatic acids were under 9.5% and 10.4%, respectively. The developed method was applied to determining the four aromatic acids in real CW samples and the spiked recoveries varied from 81.1% to 121.8%.