Quantitation of circulating hydroxyvitamin D3 in human plasma by a continuous cleanup/concentration procedure prior to HPLC-UV detection

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.