Vitamins: Fat and Water Soluble, Analysis of
Pharmaceuticals and Drugs
Published Online: 15 SEP 2006
Copyright © 2000 John Wiley & Sons, Ltd. All rights reserved.
Encyclopedia of Analytical Chemistry
How to Cite
Bates, C. J. 2006. Vitamins: Fat and Water Soluble, Analysis of. Encyclopedia of Analytical Chemistry. .
- Published Online: 15 SEP 2006
The vitamins are a diverse group of compounds, both chemically and analytically, because they comprise a range of biomolecules whose common properties reside solely in the fact that they are essential dietary components, which are needed in relatively small amounts to sustain life and good health. In addition, the major analytical challenges that they present are derived from the facts that (1) there is a need to quantitate them in a wide range of biological matrices, which include both foods and body fluids (for status indices); (2) the concentrations that are present are usually very low, and the ratio to other components, which can be chemically very similar, is small; (3) they may be present in several or many chemically diverse, but biologically interconvertible, forms; (4) some of them are labile to heat, extremes of pH, degradative enzymes and so on and (5) there is no single analytical approach that can quantitate all of them together, within a biological matrix.
They have been divided, broadly, into fat- and water-soluble groups, and each of these has been further subdivided, mainly on a functional basis. Historically, the B-group vitamins were measured by various microbiological assays, and the others were measured (if at all) by semispecific colorimetric assays. Nowadays, there are several more-powerful techniques available, which include high-pressure liquid chromatography, with a range of detectors operating over a continuous range of selective modalities; radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA)-based techniques, which use specific protein-binding selectivities; enzyme reactivation techniques for certain B-vitamin status assays, and so on. The use of mass spectrometry (MS) is gainingground and can be combined with several other separation techniques, such as gas–liquid chromatography (GLC), capillary electrophoresis (CE) and so on. Measurement of vitamins in simple pharmaceutical mixtures (vitamin supplements etc.) is now reasonably straightforward.
The technical advances that these methodologies represent have greatly broadened the horizons of the vitamin analyst, and have permitted even some of the more difficult biological matrices to be addressed. However, the unsolved challenges of accurate vitamin analysis show little sign of receding, and there are very few, if any, laboratories worldwide that are currently able to measure all of the known vitamins in all known biological matrices. This remains a major challenge and a goal for the twenty-first century.