Simultaneous HPLC–DAD Determination of Retinol and Eight Vitamin E Isomers in Human Serum

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.

A Rapid and Sensitive HPLC-FLD Method for the Determination of Retinol and Vitamin E Isomers in Human Serum

Background:

Retinol and vitamin E are fat-soluble vitamins crucial for human health, yet their isomers’ distributions in the human body are still known roughly. In order to figure out the physical condition and evaluate the nutritional status of an individual, it is imperative to analyze retinol and VE isomers in human serum.

Objective:

This work aims to establish a rapid and simple high-performance liquid chromatography with fluorescence detection for simultaneous determination of retinol and vitamin E isomers in human serum.

Methods:

Separation was accomplished on a common C18 column thermostated at 25 oC, using a simple isocratic elution program of methanol/acetonitrile (85:15, v/v) at a flow rate of 1.0 mL/min. Fluorescence detection was operated using excitation/emission wavelengths of 329 nm/472 nm for retinol and 294 nm/338 nm for VE isomers, respectively.

Results:

Rapid separation was achieved within 13 min. Linear ranges of the method were 0.020-50.0 µg/mL, with correlation coefficients greater than 0.999. Detection limits and the quantification limits were 0.001-0.004 µg/mL and 0.003- 0.013 µg/mL, respectively. Mean recoveries were 84.1%- 98.2%, with intra-day and inter-day relative standard deviations less than 12.3% and 13.6%, respectively. This method has been applied to the simultaneous determination of retinol and 8 VE isomers in human serum samples with satisfactory results.

Conclusion:

A rapid, simple and robust method was developed for routine analysis of retinol and eight vitamin E isomers in human serum, providing a useful tool for clinical diagnosis and nutritional evaluation.

Determination of tocopherols and tocotrienols in human breast adipose tissue with the use of high performance liquid chromatography-fluorescence detection

Tocopherols and tocotrienols have been extensively studied owing to their anticancer potential, especially against breast cancer. Therefore, the aim of this study was to quantitatively determine tocochromanols in human breast adipose tissue with the use of HPLC-FLD. The sample preparation procedure included homogenization and solvent extraction with isopropanol-ethanol-0.1% formic acid mixture prior to solid-phase extraction. After implementation of central composite design, satisfactory separation of all eight target compounds was achieved within 10.5 min. Chromatographic runs were carried out with the use of a naphthylethyl chromatographic column with methanol-water mixture (89:11, v/v) as the mobile phase. Fluorescence detection of tocochromanols was performed with excitation and emission wavelengths 298 and 330 nm, respectively. The method was validated in terms of linearity, carryover, recovery, precision, accuracy and stability. Extraction yield was also determined for accurate evaluation of vitamin E content in human breast adipose tissue samples. Finally, concentrations of particular tocochromanols compounds were assessed in human breast adipose tissue samples obtained from 99 patients, including women with breast cancer, healthy volunteers and deceased women who had died as a result of accidents. The raw data was transformed according to the newly developed equation for accurate estimation of the concentrations of tocochromanols in breast adipose tissue samples. Results obtained in the study indicated that the proposed analytical assay could be useful in breast cancer research.