An evaluation of cis- and trans-retinol contents in juices using dispersive liquid–liquid microextraction coupled to liquid chromatography with fluorimetric detection

Lipid-soluble vitamins from dairy products: Extraction, purification, and analytical techniques

Milk and dairy products are considered as essential sources of lipid-soluble vitamins (LSVs) for human nutrition. Due to the lower concentrations, complexity, and instability of LSVs during extraction, their quantification remains challenging. This review focus on advances in the extraction and quantification of LSVs from different dairy products. Saponification, and liquid-liquid (LLE), solid-phase (SPE), and supercritical fluid (SFE) extraction methods, as well as dispersive liquid-liquid microextraction, are the most common techniques. Liquid chromatography-mass spectrophotometry (LC-MS) has unique advantages for LSVs determination and quantification due to its high sensitivity and specificity.

An Efficient Solid-Phase Extraction-Based Liquid Chromatography Method to Simultaneously Determine Diastereomers α-Tocopherol, Other Tocols, and Retinol Isomers in Infant Formula

The separation and simultaneous quantitation of diastereomers of DL-α-tocopherol, eight tocol forms, and retinols (trans and cis) have been conducted by reversed-phase liquid chromatography followed by solid-phase extraction. A chiral silica stationary phase modified with polysaccharide derivative on the monodisperse macroporous silica gel (Unichiral OD-5H column, 150 mm × 4.6 mm, 5 μm, NanoMicro Technology Co., Ltd.) was employed for eluting each target compound. Instead of conventional solvent extract, a green and eco-friendly solid-phase extraction column, packing with nonpolar polystyrene divinylbenzene, was optimized in terms of capacity and solvent used in steps. Validation of the method was examined and confirmed to be satisfactory, with excellent linearity regression (r > 0.9999), acceptable accuracy (74.66%∼112.92%), and precision (0.20%∼10.52%) results. Limit of detection ranged from 0.05 mg·kg−1 (retinols) to 0.4 mg·kg−1 (tocols). The method was checked by infant formula reference material SRM 1849a as well, which illustrated good agreement of mass fraction with certified value and enriched the important isomer data.

A Novel Ionic Liquid-Based Liquid-Liquid Microextraction Combined with High Performance Liquid Chromatography for Simultaneous Determination of Eight Vitamin E Isomers in Human Serum

BACKGROUND

Vitamin E deficiencies are prevalent around the world and have become one of the major public health issues. It is necessary to determine their levels in human serum for routine clinical practice.

OBJECTIVE

In this study, a simple and green ionic liquid-based (IL)vortex-assisted (VA) liquid-liquid microextraction (LLME) combined with HPLC was developed for simultaneous determination of eight vitamin E isomers in human serum.

METHODS

The IL, 1-octyl-methylimidazolium trifluoromethanesulfonate ([OMIM]OTf), was added into the diluted sample and vortexed to form a cloudy solution. After centrifugation, the IL phase was collected for HPLC analysis. The separation was accomplished on a Phenomenex Luna-C18 column (250 mm × 4.6 mm, 5 μm) and the column temperature was 30°C. The mobile phase was methanol/acetonitrile (80 + 20, v/v) and the flow rate was 0.7 mL/min. A fluorescence detector was used for the simultaneous detection of eight vitamin E isomers, and the detection wavelength was set at 290/327 nm. The LLME procedure can be completed within 10 min without using any organic solvent. The parameters affecting the extraction efficiencies were optimized, including the type and volume of the ILs, dispersive solvent, vortex time, and salt addition.

RESULTS

Under the optimal conditions, limits of detection were 0.857-4.16 ng/mL. Acceptable recoveries ranging from 80.1% to 103% were achieved, with relative standard deviations less than 13.0%. The proposed method was successfully applied to the detection of eight vitamin E isomers in human serum samples.

CONCLUSIONS

This method is simple, fast, environment-friendly, cheap, and has similar linear ranges, sensitivities, accuracy, and precision as those reported chromatographic methods.

HIGHLIGHTS

The IL, [OMIM]OTf, was chosen as the green extractant of LLME for vitamin E extraction because of its strong adsorption property for vitamin E isomers. An IL-VA-LLME method has been developed for the analysis of 8 vitamin E isomers. The established method was successfully applied to the analysis of 8 vitamin E isomers in human serum samples.

Effect of seaweed supplementation on tocopherol concentrations in bovine milk using dispersive liquid-liquid microextraction

A dispersive liquid-liquid microextraction (DLLME) method, combined with HPLC-UV detection, was developed for the extraction and preconcentration of δ-tocopherol from bovine milk. This method was used to study the effect of supplementing cow feed with the seaweed Ascophyllum nodosum on vitamin content in milk. The optimal experimental conditions were determined: 200 μL of chloroform (extraction solvent), 1.0 mL of ethanol (dispersive solvent), 5 mL of water (aqueous phase). Under these optimal conditions the DLLME method provided linearity in the range 0.01 μg/mL to 8 μg/mL with R² values of 0.998. Limit of detection (LOD) was 0.01 μg/mL, while the enrichment factor was 89. Cow feed that was supplemented with Ascophyllum nodosum was shown to increase δ-tocopherol levels from 3.82 μg/mL to 5.96 μg/mL.