A convenient ultrasound‐assisted saponification for the simultaneous determination of vitamin E isomers in vegetable oil by HPLC with fluorescence detection

Abstract

An efficient ultrasound-assisted saponification was developed for simultaneous determination of vitamin E isomers in vegetable oil by high-performance liquid chromatography with fluorescence detection. The samples were saponified ultrasonically with potassium hydroxide solution for only 7 min, then the analytes were extracted with ether. Vitamin E isomers were separated on a C column at 25°C with a mobile phase of methanol/acetonitrile (81:19, v/v) at a flow rate of 0.8 mL/min. Fluorescence detection was operated at 290 nm of excitation wavelength and 327 nm of emission wavelength. Under the optimized conditions, good linearities over the range of 0.001-8.00 μg/mL (r > 0.999) were obtained. Mean recoveries of the method were 88.0-106%, with intra- and interday RSDs less than 11.8 and 12.8%, respectively. The detection limits and quantification limits of the method were 0.30-1.8 and 1.0-6.1 μg/kg, respectively. The recoveries of this method were much higher than that of the quick, easy, cheap, effective, rugged, and safe method and direct dilution method, but were similar to those of hot saponification. This proposed method provides reliable, simple, and rapid quantification of vitamin E isomers in vegetable oils. Five kinds of vegetable oils were analyzed, the quantification results were within the ranges reported by other authors.

Vitamin E in foodstuff: Nutritional, analytical, and food technology aspects

“…Ultrasound‐assisted solvent extraction has also been used (Y. Yang et al., 2018; Zhang et al., 2019). Y. Yang et al.…”

“…suggested combining saponification and ultrasound‐assisted extraction for the quantitative analysis of vitamin E isomers in vegetable oils. Ultrasound‐assisted saponification (UAS) has significantly shorter extraction time than traditional saponification and direct dilution and consequently decreases vitamin E degradation, thus proving to be stable, efficient, and low cost (Y. Yang et al., 2018). Zhang et al.…”

“…Ultrasound-assisted solvent extraction has also been used (Y. Yang et al, 2018;Zhang et al, 2019). Y. Yang et al suggested combining saponification and ultrasound-assisted extraction for the quantitative analysis of vitamin E isomers in vegetable oils.…”

“…Ultrasoundassisted saponification (UAS) has significantly shorter extraction time than traditional saponification and direct dilution and consequently decreases vitamin E degradation, thus proving to be stable, efficient, and low cost (Y. Yang et al, 2018). Zhang et al also obtained satisfactory results by using UAS to extract vitamin E, carotenoids, and phytosterols from camellia and olive oil (Zhang et al, 2019).…”

A Miniaturized Sample Preparation Method for the Determination of Vitamins A and E in Food Products

“…The potassium hydroxide (KOH) solution is commonly used for saponification, usually accompanied by an antioxidant, i.e., ascorbic acid, hydroquinone, or pyrogallol and abso-lute alcohol [27,28]. The saponification process is carried out either at room [29], or more often, at elevated (30-80 • C) temperatures using an ultrasound water bath or a standard water bath, setting the appropriate reaction time as 7 min to even 2 h [30][31][32][33]. Enzymatic hydrolysis represents an alternative to saponification, and it may provide better recoveries [28].…”