Water-soluble vitamin assay

G. F. M. Ball, Water-Soluble Vitamin Assay in Human Nutrition, Chapman Hall, Cornwell, U.K., 1994. 

GFM Ball. Water-Soluble Vitamin Assays in Human Nutrition. London Chapman Hall, 1994, pp 142-386. 

Ball GFM. Pantothenic acid. Water-soluble vitamin assays in human nutrition. New York Chapman and Hall, 1994. 

As with all modern analytical programs, an essential keystone for success is a sound analytical quality control and assessment strategy, which should always, where possible, include the exchange of samples between different analytical laboratories and the use of round-robin external quality assurance schemes. External schemes for folate and cobalam-ins are already in existence in several countries some other water-soluble vitamin assays are performed regularly by a sufficient number of different laboratories for external sample exchange schemes to be feasible and cost-effective, while others are too specialized and perhaps too rarely performed for regular... 

Gliszczyhska-Swigl, A. (2006). Antioxidant activity of water soluble vitamins in the TEAC (trolox equivalent antioxidant capacity) and the FRAP (ferric reducing antioxidant power) assays. Food Chemistry, Vol.96, No.l, (May 2006), pp. 131-136, ISSN 0308-8146. 

Assay of Water-soluble Vitamins (WSVs) in Multivitamin Tablets... 

Trolox equivalent capacity (TEAC) assay is based on antioxidants capability to reduce radical cations 2.2-azinobis(3-etilbenzotiazoline 6-sulfonat) (ABTS) and thus to inhibit absorption in the long wave part of the spectra (600 nm). Water-soluble vitamin E derivation Trolox [42] is used as a standard. 

In the area of vitamin analyses, CD spectra have been characterized for the water-soluble vitamins B2 and C. When they occur together, their distinction by direct measurement is an elementary procedure. Both were successfully assayed in the extracts of pharmaceutical... 

The antioxidant activity of alizarin was established in four different assays (1) suppression of light emission in the p-iodophenol enhanced chemiluminescent assay, (2) scavenging of superoxide anion (02 -) in a hypoxanthine-xanthine oxidase system, (3) protection of rat liver microsomes from lipid peroxidation by ADP/iron(II) ions, and (4) protection of bromobenzene-intoxicated mice from liver injury in vivo [141]. Alizarin was compared with Trolox (water soluble vitamin E), the flavonoid baicalin and green tea proanthocyanidins. In assay (1) the activity of alizarin was 76% of that of Trolox. In assay (2) the inhibition of 02 -induced chemiluminescence was 40%, 32%, 23% and 14% for Trolox, alizarin, green tea polyphenols and baicalin respectively. Alizarin was not significantly active in the lipid peroxidation assay but after baicalin the most active compound in the in vivo assay. This shows again the difficulty in the evaluation of antioxidant activity and the differences between in vitro and in vivo assays [141]. 

Three methods of detection (UV absorbance, fluorescence, and electrochemical activity) are applicable for the analysis of water-soluble vitamins. Currently, UV absorption detection is used in many LC applications for water-soluble vitamins. A simultaneous assay of several vitamins with several wavelengths along with information of peak purity can be accomplished with a diode array absorbance detector. The detection limit of a UV detector is in the order of 1-10 ng (10-100 pmol), which is poorer than that of fluorescence and electrochemical detectors but often sufficient for analysis for many vitamins in foods and physiological samples (Table 4). The lack of selectivity of UV detection may cause problems with interfering and co-eluting contaminants especially in biological samples, thus necessitating sample purification prior to LC. 

Electrochemical detection in LC provides a sensitive assay method for certain vitamins, such as AA, folates, and flavins. AA may be easily detected with femtomolar sensitivity. Sample preparation and matrix interference problems limit the routine applicability of electrochemistry in the analysis of water-soluble vitamins currently to AA. 

Immunoassays, specific protein-binding assays, and radioisotope tests are sometimes used for the determination of water-soluble vitamins. These are the only feasible and practical methods for the quantification of certain vitamins in physiological samples. The principle of competitive protein binding (CPB) using labeled radioactive or fluorescent tracer is still routinely applied to quantification of serum vitamin... 

Chromatographic methods, especially LC, have offered increased selectivity and sensitivity in vitamin assays. This is reflected in the many methodological publications on the topic over the past decades. Analyses for water-soluble vitamins in physiological samples are now performed routinely using these methods. The problems with these methods are related to sample preparation and to the sensitivity of the detection method that is used. Only a few chromatographic methods enable simultaneous assay of several water-soluble vitamins in physiological samples, and so separate assays are needed. Less complex samples (e.g., pharmaceuticals or fortified foods) are easier to analyze in this respect. 

Vitamin B12 (cobalamine) is needed to metabolize fatty adds and amino acids and to synthesize DNA in cells. Vitamin C also has several functions. It is needed to synthesize collagen, the most abundant protein in the body, but it also acts as an antioxidant, helping to reduce the risk of developing chronic diseases like heart disease and cancer. Water-soluble vitamins are not stored in the body. Because they are eliminated in urine, a continuous daily support through diet is required. However, even foods that contain the necessary vitamins can have reduced vitamin content after storage, processing, or cooking. Therefore, many people take a multivitamin tablet to supplement their diet. To ensure that these tablets contain the labeled amounts of vitamins, there must be a quality control assay for these tablets. 

Assay of B Vitamins and other Water-soluble Vitamins in Honey... 

The development of specific analytical methods for determining water-soluble vitamins in such matrix has not seen major activity in past decades. In the early years, microbiological and colorimetric assays were normally used for this task, while in more recent times, analytical procedures assessed for measuring vitamins in other matrices have been extended to honey, sometimes with questionable results. Only in the last decade has the attention of a number of research groups resulted in specialized and validated HPLC methods. 

Tsukatani, T., Suenaga, H., Ishiyama, M., Ezoe, T., and Matsumo, K., 2011. Determination of water soluble vitamins using a colorimetric microbial viability assay based on the reduction of water-soluble tetrazolium salts. Food Chemistry. 127 711-715. 

---