Determination of vitamins D2, D3, K1 and K3 and some hydroxy metabolites of vitamin D3 in plasma using a continuous clean-up-preconcentration procedure coupled on-line with liquid chromatography-UV detection

A concise review of quantification methods for determination of vitamin K in various biological matrices

Vitamin K is an essential nutrient in the body and involved in numerous physiological and pathophysiological functions. Both the lack and surplus of vitamin K can put human health at risk. Therefore, it becomes necessary to monitor vitamin K concentrations in different biomatrices through establishing sensitive and specific analytical methods. This review collectively describes an updated overview of the sample pretreatment methodologies and methods for quantitative determination of vitamin K that have been used in last two decades. High Performance Liquid Chromatography (HPLC) is commonly utilized as a standard for separation of vitamin K in combination with different detection including spectroscopic, spectrometric, fluorometric and mass spectroscopy. Recent progress in sample pretreatment technologies and quantitation methodologies have enhanced the ability to identify and quantitate vitamin K in biomatrices to further advance our understanding of the role of this vitamin in human health and disease.

Liquid Chromatography Analysis of Common Nutritional Components, in Feed and Food

Food and feed laboratories share several similarities when facing the implementation of liquid-chromatographic analysis. Using the experience acquired over the years, through application chemistry in food and feed research, selected analytes of relevance for both areas were discussed. This review focused on the common obstacles and peculiarities that each analyte offers (during the sample treatment or the chromatographic separation) throughout the implementation of said methods. A brief description of the techniques which we considered to be more pertinent, commonly used to assay such analytes is provided, including approaches using commonly available detectors (especially in starter labs) as well as mass detection. This manuscript consists of three sections: feed analysis (as the start of the food chain); food destined for human consumption determinations (the end of the food chain); and finally, assays shared by either matrices or laboratories. Analytes discussed consist of both those considered undesirable substances, contaminants, additives, and those related to nutritional quality. Our review is comprised of the examination of polyphenols, capsaicinoids, theobromine and caffeine, cholesterol, mycotoxins, antibiotics, amino acids, triphenylmethane dyes, nitrates/nitrites, ethanol soluble carbohydrates/sugars, organic acids, carotenoids, hydro and liposoluble vitamins. All analytes are currently assayed in our laboratories.

Separation and determination of Vitamins E and A in multivitamin syrup using micellar liquid chromatography and simplex optimization

A rapid method has been described for separation and determination of Vitamins A and E using micellar liquid chromatography (MLC). Influence of temperature of column and addition of organic modifiers on separation efficiency was investigated. A temperature of 30 degrees C and 1-butanol modifier was selected. Optimization of the parameters affecting the separation including percent of organic modifier, pH of the mobile phase, concentration of surfactant, and flow rate of the mobile phase was performed simultaneously using the super-modified simplex (SMS) procedure. Results showed that 11.7% 1-butanol, 76.9 mM sodium dodecyl sulphate (SDS), pH of 6.73 and a flow rate of 1.35 ml min(-1) are the best conditions for separation of these compounds. The analytical parameters including linearity, r>0.9990; limit of detection 1.71 and 4.52 microg ml(-1) for A and E, respectively; precision of the method, R.S.D.<2.85%; and recovery, more than 90%, show that the method is useful for measuring these compounds in pharmaceutical preparations.

Development of a validated liquid chromatography method for the simultaneous determination of eight fat-soluble vitamins in biological fluids after solid-phase extraction

In the present study, a simple and rapid reversed-phase HPLC procedure has been developed for the simultaneous determination of eight fat-soluble vitamins (retinol, menadione, menaquinone, delta-tocopherol, cholecalciferol, alpha-tocopherol, alpha-tocopherol acetate and phylloquinone) in biological fluids: blood serum and urine. The analytical column, Phenomenex Luna C18 (150 mm x 4.6 mm) 3 microm, was operating at ambient temperature. Mobile phase consisted of a mixture of CH3OH-CH3CN delivered using a linear gradient, starting with a composition of 50-50% v/v and ending at 30-70% at a flow rate of 1.3 ml/min. Xanthophyll was used as internal standard (2 ng/microl). Detection and identification was performed using a photodiode array detector. Eluent monitoring was achieved at 280 nm for vitamins and 450 nm for the internal standard. However, quantitation was performed at maximum wavelength for each vitamin. Detection limits were found in the range of 1.4-6.6 ng per 20-microl injected samples, while linearity held up to 25 ng/microl. The statistical evaluation of the method was examined performing intra-day (n = 6) and inter-day calibration (n = 7) and was found to be satisfactory, with high accuracy and precision results. The biological fluids were treated using solid-phase extraction cartridges, to remove all endogenous interferences from sample matrix. The solid-phase extraction protocol was optimized in terms of retention and elution. High extraction recoveries from biological matrices: blood serum and urine, (average recovery ranging between 95 and 97.6% for blood serum and between 94.2 and 95.8% for urine) were achieved for the eight fat-soluble vitamins, using Cyclohexyl J.T. Baker SPE cartridges with methanol as eluent, requiring small volumes, 100 microl of blood serum and 100 microl of urine.

Automated method for the determination of fat-soluble vitamins in serum

A new fully automated high-performance liquid chromatography (HPLC) method using 1 ml of serum has been developed for the determination of retinol (Vitamin A), alpha-tocopherol (Vitamin E), 25-hydroxyvitamin D(3) and 24 R,25-hydroxyvitamin D(3). The eluate was monitored with a photodiode-array detector at three wavelengths-namely: 265 nm for Vitamin D(3), 291 nm for Vitamin E and 325 nm for Vitamin A. The detection limits were equal to or lower than 1 ng ml(-1) for all vitamins. The linearity obtained with serum samples (standard addition method) gives correlation coefficients (r(2)) ranging between 0.999 and 0.996 in all cases, with standard deviation of the slope between 3.2 and 1.6%. The repeatability was between 4.0 and 6.0% and the within-laboratory reproducibility was lower than 10% in all cases. The most outstanding features of the present method are its ease of use, its rapidity and fully automation, which enables its use for routine analysis. The time required per sample was 30 min, because the overlapped development of the steps. This method was used for the determination of normality range of these vitamins in healthy people in the 18-80-year-old interval.

Fully automated method for the determination of 24,25(OH)2 and 25(OH) D3 hydroxyvitamins, and Vitamins A and E in human serum by HPLC

A new fully automated method for the determination of metabolites of Vitamin D(3) and Vitamins A and E has been developed. A robotic station for liquid-liquid extraction, connected on line with an automatic system for solid-phase extraction (Prospekt) and a liquid chromatograph were used and the complexity of the overall method was overcome by full automation. The eluate from the chromatograph was monitored by a photodiode-array detector at three wavelengths, namely, 265 nm for Vitamin D(3) metabolites, 291 nm for Vitamin E and 325 nm for Vitamin A-which are the maximum absorption wavelengths for the analytes. The time required per sample analysis was 35 min because of the overlapping development of the steps. The linearity obtained for serum samples (standard addition method) gives correlation coefficients (r(2)) ranging between 0.996 and 0.989, with standard deviation of the slope between 4.0 and 4.9%. The repeatability was between 4.0 and 6.0% and the within-laboratory reproducibility was lower than 10.1% in all cases-both expressed as relative standard deviation-for low concentrations of the analytes, namely, 3 ng/ml for 24,25(OH)(2) dihydroxyvitamin D(3), 10 ng/ml for 25(OH) hydroxyvitamin D(3), 100 ng/ml for Vitamin A and 2 microg/ml for Vitamin E. The method has been validated using a CRM (NIST, SRM968c).

Simultaneous quantification of Vitamins A, D3 and E in fortified infant formulae by liquid chromatography–mass spectrometry

A novel method for the simultaneous quantification of Vitamins A, D3 and E in fortified infant formulae has been developed using isocratic normal-phase liquid chromatography with positive atmospheric pressure chemical ionization mass spectrometry (LC-APCI-MS). Food products were saponified and the vitamins were extracted by solid-phase extraction (SPE) on a Chromabond XTR cartridge. Quantification of Vitamins D3 and E were performed with Vitamin D2 and 5,7-dimethyltocol (DMT) as internal standards (IS), respectively while no IS was used for Vitamin A. Detection of the vitamins was made in the selected ion monitoring (SIM) mode. MS calibration curves were linear between 0.15 and 12 mg/l for Vitamin A, 5-400 microg/l for Vitamin D3 and 0.25-20 mg/l for Vitamin E with regression coefficient r2 > 0.996 and the limits of detection were below 1.4 ng. The repeatability (CV) obtained on a reference dietetic infant formula was 2.3% for Vitamin A, 2.6% for Vitamin E and 5.9% for Vitamin D3. The between-day variations (CV) over 6 days were in the ranges of 2.4-6.9% for the three vitamins. The mean recoveries from a reference infant formula spiked with all three vitamins ranged from 96 to 105% with a relative standard error less than 9%. The applicability of the method was demonstrated by analyzing a set of infant formula and infant cereals; similar results were obtained with the LC-MS method and reference HPLC methods.

Gas chromatography and high-performance liquid chromatography of natural steroids

This review article underlines the importance of gas chromatography (GC), high-performance liquid chromatography (HPLC) and their hyphenated techniques using mass spectrometry (MS) for the determination of natural steroids, especially in human biological fluids. Steroids are divided into eight categories based on their structures and functions, and recent references using the above methodologies for the analysis of these steroids are cited. GC and GC-MS are commonly used for the determination of volatile steroids. Although HPLC is a widely used analytical method for the determination of steroids including the conjugated type in biological fluids, LC-MS is considered to be the most promising one for this purpose because of its sensitivity, specificity and versatility.

Extraction of fat-soluble vitamins

An overview of the different extraction procedures of fat-soluble vitamins from human fluids, foods and pharmaceutical preparations is presented. Methods using organic solvent extraction (both liquid-liquid and solid-liquid extraction), supercritical fluid extraction and solid-phase extraction for the different types of both vitamins and matrices are discussed.

Rapid and sensitive high-performance liquid chromatographic method for simultaneous determination of retinol, alpha-tocopherol, 25-hydroxyvitamin D3 and 25-hydroxyvitamin D2 in human plasma with photodiode-array ultraviolet detection

A new rapid and sensitive high-performance liquid chromatographic method using 0.5 ml of plasma has been developed for the simultaneous determination of retinol (vitamin A), alpha-tocopherol (vitamin E), 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3. The eluate was monitored with a photodiode-array detector with two fixed wavelengths (267 nm for vitamin D, 292 nm for alpha-tocopherol and retinol). For all compounds, including internal standards, the method provides extraction recoveries greater than 81%. Detection limits were equal to or lower than 1.5 microg/l for the 4 vitamins. Linearity of standards was excellent (r>0.999 in all cases). Intra-day and inter-day precision were generally acceptable; the intra-dayassay C.V. was 3/4 7.7 for all compounds and the inter-day-assay C.V. was <9.2% except for the lower concentrations of 25-hydroxyvitamin D3, 25-hydroxyvitamin D2 and alpha-tocopherol (10.8, 11.8 and 11.9, respectively). The important properties of the present method are its ease of use, its rapidity, since sample preparation was achieved in 15 min and all the compounds were eluted in less than 15 min, and its small sample volume required (=0.5 ml), which enables it to be used in pediatric practice.

Solid-phase trapping of solutes for further chromatographic or electrophoretic analysis

Because of its simplicity, speed and effectiveness, solid-phase extraction (SPE) has become the preferred technique for concentration of selected analytes prior to chromatographic or electrophoretic analysis. In this review the historical development of SPE is briefly traced. Then the principles of SPE are reviewed in some detail. Numerous references are given on the format, sorbents, elution conditions, online techniques and automation with special emphasis on relatively recent developments. The principles and recent advances in solid-phase microextraction (SPME) are also reviewed. The final section on selected recent applications includes an extensive list of references to work published within the last three years. Future trends and developments are discussed briefly.