Vitamin assay methods

Assoc. Vitamin Chemists, Methods of Vitamin Assay," New York, Interscience Publishers,... 

Microbiological assay should stress accuracy over precision. Standardization of an assay method should include comparisons with at least one other organism having a different nutritional pattern and specificity toward the compound being assayed. Such a comparison was made for cyanocobalamin (vitamin Bi2 ) content of human blood and serum, using four microorganisms differing in their cobamide requirements and metabolism (B9). 

The chemistry, metabolism, and clinical importance of folic acid have been the subject of many excellent reviews (A7, Gil, H14, H20, Rl). Folic acid deficiency leads to a macrocytic anemia and leucopenia. These symptoms are due to inadequate synthesis of nucleic acid. The synthesis of purine bases and of thymine, required for nucleic acid synthesis, is impaired in folic acid deficiency. Detection of folic acid activity in biologic fluids and tissues is of the utmost importance it distinguishes between the various anemias, e.g., those due to vitamin Bi2 or folic acid deficiency. Because morphology of the abnormal red cell does not help in diagnosing vitamin deficiency, one must rely on assay methods for differential diagnosis. Treatment of pernicious anemia with folic acid has led to subacute combined degeneration of the spinal cord despite... 

A modification of the above serum folic assay method was recently described (W4). The investigators confirmed the validity of this technique as a practical means of differentiating patients with folic acid from vitamin B12 megaloblastic anemias. Another modification of this method was also described (C4). These investigators reduced the over-all sensitivity by high serum dilutions and thus made the assay, as they used it, valueless as a diagnostic tool. 

A10. Association of Vitamin Chemists, Inc., in Methods of Vitamin Assay, pp. 69-97. Interscience, New York, 1947. 

Malabsorption Syndrome, with Special Reference to the Effects of Wheat Gluten (Frazer), 5, 69 Mellituria, Nonglucose (Sidbury), 4, 29 Microbiological Assay Methods for Vitamins (Baker and Sobotka), 5, 173 Organic Acids in Blood and Urine (Nordmann and Nordmann), 4, 53 Paper Electrophoresis Principles and Techniques (Peeters), 2, 1 Paper Electrophoresis of Proteins and Protein-Bound Substances in Clinical Investigations (Owen), I, 238 Parathyroid Function and Hyperparathyroidism, Biochemical Aspects of (Nordin), 4, 275... 

Vitamin Br, Absorption, Distribution, and Excretion, Physiology and Pathology of (Grasbeck), 3, 299 Vitamins, Microbiological Assay Methods for (Baker and Sobotka), 5, 173... 

Microbiological Assay Methods for Vitamins Herman Baker and Harry Sobotka... 

One of the more important areas of use of ultraviolet instruments is the identification and determination of biologically active substances. Many components in body fluids can be determined either directly or through colorimetric methods. Drugs and narcotics can be measured both in the body as well as in formulations. Vitamin assay is another related activity. Nearly all metals and nonmetals can be determined through their ultraviolet absorption or by colorimetric methods. In recent years, ultraviolet instruments have been used extensively for the determination of air and water pollutants, such as aldehydes, phenolics, and ozone ... 

ER Elkins, JA Dudek. Sampling for vitamin analyses. In J Augustin, BP Klein, D Becker, PB Venu-gopal, eds. Methods of Vitamin Assay. 4th ed. New York Wiley, 1985, pp 135-151. 

ID Desai. Assay methods. In LJ Machlin, ed. Vitamin E. A Comprehensive Treatise. New York Marcel Dekker, 1980, pp 67-98. 

Association of Vitamin Chemists. Vitamin E (tocopherols). Methods of Vitamin Assay. 3rd ed. New York Interscience, 1966, pp 363-402. 

EJ de Vries, J Zeeman, RJE Esser, B Borsje, FJ Mulder. Analysis of fat-soluble vitamins. XXI. High pressure liquid chromatographic assay methods for vitamin D in vitamin concentrates. J Assoc Off Anal Chem 62 129-135, 1979. 

Common HPLC detectors lack the sensitivity and selectivity to determine the low concentrations of the endogenous B,2 vitamers in foods. As a result, vitamin Bl2 method development for food samples has concentrated on ligand binding and microbiological assays no reviews of HPLC methods have been published. 

Tani, et al. (32) have described a paper disc assay method to screen the biosynthetic intermediates of vitamin Bg. 

Concerning the etiology of idiopathic hypercalcemia, an interesting report has come from Fellers and Schwartz (F3b). By bio-assay methods they estimated the vitamin D-like activity of the serum of two severe cases of idiopathic hypercalcemia and found increased activity. They further found that this increased activity persisted unchanged for periods... 

In 1926 Minot and Murphy (4) announced that whole liver was effective in the treatment of pernicious anemia. The initial assay methods, which were clinical (5), coupled with what we now know are the exceptionally small amounts of Bi2 (even in a relatively rich source such as liver) required that two more decades pass before Folkers (6) and Smith (7) in 1948 simultaneously isolated crystalline vitamin Bi2 (1, R = CN). A further decade passed before it was realized that the so-called vitamin (cyanocobalamin) was an artifact of the isolation procedure and that the enzymatically active species is the vitamin Bi2 coenzyme (5 -deoxyadenosylcobalamin, 1, R = 5 -deoxyadenosyl). This initial observation arose during Barkers study on the conversion... 

Because it is a potent reducing agent, vitamin C is commonly determined by titrimetric orpotentiometric redoxmethods. Such methods underestimate the amount of the vitamin present because dehydroascorbate - which has vitamin activity - is formed by atmospheric oxidation of ascorbate in the sample, especially under neutral conditions, and is not detected by redox assay methods. 

Miscellaneous.—The sensitivity of the Zimmermann colour reaction for 17-oxo-steroids (alkaline m-dinitrobenzene) and the stability of the colour vary according to the base used. Assay methods for the active hydroxylated derivatives of vitamin D have been reviewed. ... 

A number of assay methods for vitamin Bu status, and for testing defects in the pathway of vitamin B,j absorption, arc listed here ... 

R. Strohecker and H. M. Henning, Vitamin Assay, Tested Methods, Verlag Chemie, Weinheim, 1966. 

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