Determination of carbendazim and thiabendazole in apple juice by hollow fibre-based liquid phase microextraction-high performance liquid chromatography with fluorescence detection

A hollow fibre-based liquid phase microextraction (HF-LPME) coupled with high performance liquid chromatography with fluorescence detection (HPLC-FD) method was developed for the determination of carbendazim (MBC) and thiabendazole (TBZ) in apple juice. Some important extraction parameters, such as the pH of the sample solution, extraction time, stirring rate and salt concentration, were optimised. As a result, the optimal HF-LPME conditions were selected as follows: A 4 mL of sample solution (donor phase) at pH of 7.5 was used for the extraction. The pores of the hollow fibre were impregnated by 1-octanol, and 5mM HCl (pH = 2.5) was used as the extraction solvent. The extractions were conducted at a stirring rate of 800 rpm for 40 min. After extraction, 10 mu L of the extraction solvent was injected into the HPLC system for analysis. The average enrichment factors were 106 and 114 for MBC and TBZ, respectively. A good linear relationship existed in the range of 2.5 similar to 500 mu g L-1 and 5 similar to 500 mu g L-1 for MBC and TBZ in apple juice with the correlation coefficients (r) of 0.9995 and 0.9991, respectively. The limits of detection were 0.8 mu g L-1 for MBC and 1.5 mu g L-1 for TBZ (S/N = 3 : 1). The recoveries of the method were between 86.3% and 106.0% with the relative standard deviations (RSDs) ranging from 3.3% to 8.5%. The HF-LPME-HPLC method has been successfully applied to the analysis of MBC and TBZ in apple juice, indicating that LPME-HPLC may be a promising combination for the analysis of pesticide residues for some food samples.