Selective extraction and enrichment of 5-hydroymethylfurfural from honey, molasses, jam and vinegar samples prior to sensitive determination by micro-volume UV-vis spectrophotometry

Abstract

In this study, a new method was developed for the extraction/enrichment of 5-hydroxymethylfurfural (5-HMF) from sample matrix prior to analysis. The method is based on the selective formation of the imine adduct and ion-pair between 5-HMF and phenosafranine (weak base, PSF+) in the presence of sodium dodecyl sulfate (SDS) at pH 5.5 by the base induced disproportionation. Then, the complexes were enriched into the micellar phase of Triton X-114, diluted with ethanol, and detected at 532 nm by micro-volume UV–vis spectrophotometry. The variables affecting extraction efficiency were optimized. In optimal conditions, the calibration curves were over the range of 2−100 and 2−200 μg L−1 with the detection limits of 0.53 and 0.75 μg L−1 using 0.2 and 3.0 mL of 1.0 × 10-3 mol L−1 SDS. From enrichment of 15-mL sample, an enrichment factor of 37.5-fold was obtained. The accuracy/ precision studies after spiking were performed, and observed to be in range of 97.3–102.3 % and 2.5−3.8% (10, 25 and 75 μg L−1, n: 5). After validation, the method was applied to the analysis of the selected foods. From the results, it was observed that 5-HMF levels were in the range of 1.05–18.10 mg kg−1 with a RSD% of 3.0–4.2 % and recovery of 95.5–98.0 % by sample extraction with sonication while they ranged from 1.15–18.05 mg kg−1 with a RSD% of 3.0–4.2 % and recovery of 95–99 % without sonication. Finally, it was observed that the results obtained were in agreements with those of the modified White method, statistically validating the method.