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Riboflavin assay

Three recent reviews specifically cover HPLC methods for quantitating riboflavin in foods. In addition to HPLC methods, Nielsen (81) summarized paper chromatography, TLC, and open-column chromatography procedures for quantitating total riboflavin and the individual vitamers in foods, pharmaceuticals, and biological samples. Russell (44) included a brief discussion of the standard methods, along with HPLC and flow injection analyses published between 1990 and 1994 for total riboflavin and the individual vitamers in foods. Ball (45) reviewed HPLC methods for quantitation of riboflavin, as well as chemical and microbiological riboflavin assays for foods. [Pg.425]

Identification A 1.5 100 (w/v) aqueous solution responds to the Identification Test in the monograph for Riboflavin. Assay Not less than the equivalent of 73.0% and not more than the equivalent of 79.0% of riboflavin (Ci7H2oN4Og), calculated on the dried basis. [Pg.384]

The results of riboflavin assays of 20 liver biopsy specimens from patients without liver disease were reported by Imanaga et al. (1953). The observed tissue contents showed no definite variation with age, the calculated mean values, expressed as milligrams per cent, being 20-29 years, 2.49 (N = 5) 30-39 years, 2.53 (V = 2) 40 9 years, 2.70 N = II) and 50-59 yesirs, 2.57 (V = 2).. ... [Pg.78]

The use of solid-phase extraction cartridges is now well established in the analysis of clinical specimens. However, although this method provides efficient purification of the sample, it may lead to a loss of protein-bound vitamins. Direct injection of plasma samples into liquid chromatography (LC) columns is possible in some applications. Dilute filtered or centrifuged urine can be injected in certain LC applications, as is the case in urinary riboflavin assay. [Pg.4919]

Snell and Strong (363, 364) developed the growth response of Lactobacillus casei to riboflavin as an assay method, and it was soon used, for example by Fraser, Topping, and Isbell (102) to assay riboflavin in the urine and tissues of normal and riboflavin-deficient dogs. The microbiological riboflavin assay has since been widely used e.g., 394). [Pg.137]

Riboflavin can be assayed by chemical, en2ymatic, and microbiological methods. The most commonly used chemical method is fluorometry, which involves the measurement of intense yeUow-green fluorescence with a maximum at 565 nm in neutral aqueous solutions. The fluorometric deterrninations of flavins can be carried out by measuring the intensity of either the natural fluorescence of flavins or the fluorescence of lumiflavin formed by the irradiation of flavin in alkaline solution (68). The later development of a laser—fluorescence technique has extended the limits of detection for riboflavin by two orders of magnitude (69,70). [Pg.79]

The microbial assay is based on the growth of l ctobacillus casei in the natural (72) or modified form. The lactic acid formed is titrated or, preferably, the turbidity measured photometrically. In a more sensitive assay, l euconostoc mesenteroides is employed as the assay organism (73). It is 50 times more sensitive than T. casei for assaying riboflavin and its analogues (0.1 ng/mL vs 20 ng/mL for T. casei). A very useful method for measuring total riboflavin in body fluids and tissues is based on the riboflavin requirement of the proto2oan cHate Tetrahjmenapyriformis which is sensitive and specific for riboflavin. [Pg.79]

Although riboflavin can be assayed more readily by chemical or microbiological methods than by animal methods, the latter are preferred for nutritional studies and as the basis of other techniques. Such assays depend upon a growth response the rat or chick is the preferred experimental animal. This method is particularly useful for assaying riboflavin derivatives, since the substituents frequently reduce or eliminate the biological activity. [Pg.79]

The recognition of their structure permits the determination of vitamins by the tools of analytical chemistry, but while such methods are widely used in industrial production, the minute quantities in body fluids and tissues limit the purely chemical approach to a few members of this group present in relatively high concentration, e.g., vitamin C (K5). Microchemical methods are in use for the determination of thiamine, riboflavin, and some of the fat-soluble vitamins, based on the most sensitive colorimetric and, in particular, fluorometric techniques. Vitamin D, on the other hand, is determined by animal assay. [Pg.189]

The same authors (G8, G7) also found very substantial decreases in riboflavin (approx. 80%), and niacin (P9) fared little better. When mixtures were irradiated unusual events occurred. Riboflavin and ascorbic acid were each protected by niacin. Addition of cystine or cysteine apparently sensitized the niacin (P10). Since initial rates were not given, and the doses were considerably above the oxygen breakpoint (Sec. IIIA2), no mechanistic interpretation is possible. There also appears to be some doubt about the reliability of the colormetric assay used by these workers. [Pg.406]

The determination of vitamins in pharmaceutical preparations continues to receive considerable attention. The voltammetric oxidation of vitamin A at a carbon paste electrode in the presence of vitamin E, a potential source of error in the assay, has been described [142,143]. Other assays involve the polaro-graphic determination of niacinamide [144-146], menadione (vitamin K3) [147], riboflavin (vitamin B2) [148], thiamine, riboflavin, and nicotinamide in multivitamin preparations [149], and multivitamins [150]. [Pg.795]

Kawasaki (68) briefly reviewed HPLC methods for determining total thiamine alone and in combination with riboflavin. Russell (44) provided a more detailed summary of HPLC methods, published between 1990 and 1994, for thiamine alone and in conjunction with other vitamins. Ball (45) reviewed selected HPLC analyses for thiamine in various foods, as well as other chemical and microbiological assays. [Pg.417]

If time permits, dilute the riboflavin and adenosine samples twofold and measure the absorbances of these samples at the same wavelengths used to calculate the molar extinction coefficients (450 nm for riboflavin and 260 nm for adenosine). If Beer s law holds true for these compounds, each of these assays should yield the same molar extinction coef-... [Pg.22]

Later in the Second World War, Bradford worked at the Charterhouse Rheumatism Clinic, London, from where she coauthored papers on winter sources of vitamin C and on the determination of riboflavin in blood. After the war, she was employed by J. C. Lyons Co. Ltd., from where she authored four papers for The Analyst two on riboflavin in tea, one on the microbiological assay of vitamins, and one on the use of a single tap source to simultaneously run three different applications. Later in life, Bradford married Mr. Bentley and became a Consultant. She died on 20 August 1981, aged 79 years. [Pg.492]

Darby, W. J. (1972) Application of the erythrocyte glutathione reductase assay in evaluating riboflavin nutritional status in a high school student population. Am. J. Clin. Nutr. [Pg.85]

Photolysis of riboflavin leads to the formation of lumiflavin in alkaline solution and lumichrome in acidic or neutral solution (see Figure 7.2). Because lumiflavin is chloroform extractable, photolysis in alkaline solution, followed by chloroform extraction and fluorimetric determination, is the basis of commonly used chemical methods of assaying riboflavin. The photolysis proceeds by way of intermediate formation of cytotoxic riboflavin radicals, and the addition of riboflavin and exposure to light has been suggested as a means of inactivating vimses and bacteria in blood products (Goodrich, 2000). [Pg.175]

The riboflavin binding protein that occurs in eggs has been exploited for the radio-ligand binding assay of riboflavin. Because binding to the protein quenches the native fluorescence of riboflavin, it can be exploited for a direct titrimetric fluorescence assay of the vitamin in urine and other biological samples (Kodentsova et al., 1995). [Pg.178]

Spectrofluorimetry differs from absorption spectrophotometry in not yielding an absolute scale of values. For this reason it is essential to employ a reference standard for quantitative measurements. For example, some pharmacopoeial tests, such as the test for uniformity of content for digitoxin tablets, employ a spectrofluorimefric assay and comparison wi an ofticial reference standard. Quantitative Spectrofluorimetry has been proposed for a munber of naturally fluorescent compoimds, including ergometrine, riboflavine, tiie catechol-amines, phenothiazines, the barbiturates (at pH 13), and certain antibiotics such as chlortetracycline and oxytetracycline. [Pg.235]

Flavins are lost from the body as intael riboflavin, rather than as a breakdown product of riboflavin. Hence, vitamin status may be assessed by measuring the level of urinary riboflavin. Generally, the loss of 30 ig of riboflavin/g creatinine or less per day indicates a deficiency. This metht>d of assessment is not preferred because it is influenced by a number of factors unrelated to vitamin status. Another problem with this method is its great sensitivity to a short-term deficiency thus, it does not necessarily reflect the true concentrations of FAD and FMN in tissues. The most reliable way to assess riboflavin status is by a functional test. The test involves the assay of glutathione reductase, using red blood cells as the source of... [Pg.612]

Glutathione is discussed further in the section on selenium and glutathione in Chapter 10. The enzyme assay is conducted using glutathione reductase extracted from red blood cells with and without added FAD. Chmnic consumption of a diet deficient in riboflavin allows the continued synthesis of a variety of flavoproteins, but results in the accumulation of apoenzyme without its conversion to holoen-zyme. Addition of chemically pure FAD to a biological fluid containing apoenzyme results In the stimulation of enzyme activity because of the formation of the holoenzyme. It is this stimulation of enzyme activity that is used to determine vitamin status in humans. [Pg.613]

Saubcriich, H. E., Judd, J. H., Nichoalds, C. F.., Broquist, H. P, and Darby, W. J, (1972). Application of the erythrocyte glutathione reductase assay in evaluating riboflavin status in a high school student population. Am. /. Cfjri. Nutr, 25, 756-762. [Pg.665]


See other pages where Riboflavin assay is mentioned: [Pg.79]    [Pg.79]    [Pg.79]    [Pg.79]    [Pg.329]    [Pg.20]    [Pg.16]    [Pg.19]    [Pg.583]    [Pg.284]    [Pg.1549]    [Pg.154]    [Pg.296]    [Pg.583]    [Pg.133]    [Pg.351]    [Pg.81]    [Pg.81]    [Pg.175]    [Pg.175]   
See also in sourсe #XX -- [ Pg.135 ]




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