Ascorbic acid, determination determining

Bertotti, M. Vaz, J. M. Telles, R. Ascorbic Acid Determination in Natural Orange Juice, /. Chem. Educ. 1995, 72, 445M47. 

The following polyvitamin prepai ations were analyzed Kal tsid (OAO Comfort Plus , Russia), Asvitol (OAO INC Marbiofarm , Russia), Pikovit (KRKA, d.d. The New Place, Slovenia), Yeast with vitamin C (000 EKKO Plus , Russia). Chromatographic experiment has been carried out using Silufol UV-254 (Kavalier, Czech Republic) and acetone - ethyl acetate - acetic acid - ethanol (3 5 1 1) - CTAB (2T0 M) as a mobile phase mixture. The linearity calibration plot, built in coordinate S = f (IgqAC), is valid in the interval 5-25 p.g. Correctness of the determination has been checked by photometry. The obtained results for the ascorbic acid determination are presented below. 

This capacity is applicable in various sectors of the food industry such as bioremediation, beverage processing, ascorbic acid determination, sugar-beet pectin gelation, and baking it also acts as a biosensor. 

E. Turkusic, V. Milicevic, H. Tahmiscija, M. Vehabovic, S. Basic and V. Amidzic, Amperometric sensor for L-ascorbic acid determination based on Mn02 bulk modified screen printed electrode, Fresenius J. Anal. Chem., 368 (2000) 466-470. 

Ascorbate electrodes for ascorbic acid determination in food (251), fruit juices (252) or pharmaceutical preparations (253) are based on the following reaction ... 

Chromatographic methods, notably hplc, are available for the simultaneous determination of ascorbic acid as well as dehydroascorbic acid. Some of these methods result in the separation of ascorbic acid from its isomers, eg, erythorbic acid and oxidation products such as cHketogulonic acid. Detection has been by fluorescence, uv absorption, or electrochemical methods (83—85). Polarographic methods have been used because of flieti accuracy and their ease of operation. Ion exclusion (86) and ion suppression (87) chromatography methods have recently been reported. Other methods for ascorbic acid determination include enzymatic, spectroscopic, paper, thin layer, and gas chromatographic methods. Excellent reviews of these methods have been published (73,88,89). 

Lee W, Roberts SM, Labbe RF. Ascorbic acid determination with an automated enzymatic procedure. Clin Chem 1997 43 154-7. 

Veazey RL, Nieman TA. Chemiluminescence high-performance liquid chromatographic detector applied to ascorbic acid determinations. J Chromatogr, 1980 200 153-62. 

A.P.S. Paim, B.F. Reis, An automatic spectrophotometric titration procedure for ascorbic acid determination in fruit juices and soft drinks based on volumetric fraction variation, Anal. Sci. 16 (2000) 487. 

There are two standard (AOAC) procedures for vitamin C (ascorbic acid) determination in fruits and fruit products. The sample preparation is common to both and involves maceration/dilution of the sample in a stabilizing solution such as 5% metaphosphoric acid or trichloroacetic acid followed by filtration. The ascorbic acid can then be determined by titration with 2,6-dichloroindophenol, where the ascorbic acid reduces the redox indicator dye to a colorless solution, or by fluorimetric detection, in which the ascorbic acid is oxidized to dehydroascorbic acid, which then reacts with o-phenylenediamine to produce a fluorophore. The latter method has the advantages that it is suitable for colored solutions and can also be used to measure levels of naturally occurring dehydroascorbic acid as well as ascorbic acid. Many other methods are available for determination of vitamin C, with the use of LC techniques currently the subject of much interest. Reversed-phase LC techniques can be used to determine both dehydroascorbic acid, ascorbic acid and their isomers. 

Ascorbic acid (vitamin C) appears naturally in most fresh fruits and fruit juices but is often added during the manufacture of juices or soft drinks as a preservative or antioxidant. A simple, fast, and direct SIA method for ascorbic acid determination in juices was... 

Flow Injection Analysis Methods for Ascorbic Acid Determination 300... 

Mattos, I. L., F. Padilla, J. H. Zagal, E. H. L. Falcao, and R. Segura. 2011. Screen-printed electrode modified with silver hexacyanoferrate-nafion for ascorbic acid determination. /. Chil. Chem. Soc. 56 803-807. 

Schaffar, B. P. H., B. A. A. Dremel, and R. D. Schmid. 1989. Ascorbic acid determination in fruit juices based on a fiber optic ascorbic acid biosensor and flow injection analysis. In Biosensors Applications in Medicine, Environmental Protection and Process Control, eds. R. D. Schmid, and F. Scheller, pp. 229-232. New York VCH Publishers. 

Marques, I. D. H. C., E. T. A. Marques, A. C. Silva, W. M. Ledingham, E. H. M. Melo, V. L. da Silva, and J. L. Lima Filho. 1994. Ascorbic acid determination in biological fluids using ascorbate oxidase immobilized on alkylamine glass beads in a flow injection potentiometric system. Appl. Biochem. Biotechnol. 44 81-89. 

Goreti, M., F. Sales, M. S. A. Castanheira, R. M. S. Ferreira, M. Carmo, V. G. Vaz, and C. Delerue-Matos. 2008. Chemically modified carbon paste electrodes for ascorbic acid determination in soft drinks by flow injection amperometric analysis Portugaliae. Electrochim. Acta 26 147-157. 

The content of ascorbic acid, in milligrams per 100 mL, in orange juice is determined by a redox titration using either 2,6-dichlorophenolindephenol or N-bromosuccinimide as the titrant. 

This experiment describes the use of FIA for determining the stoichiometry of the Fe +-o-phenanthroline complex using the method of continuous variations and the mole-ratio method. Directions are also provided for determining the stoichiometry of the oxidation of ascorbic acid by dichromate and for determining the rate constant for the reaction at different pH levels and different concentration ratios of the reactants. 

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