Addition of ascorbic acid

It is therefore possible to determine cations such as Ca2+, Mg2+, Pb2+, and Mn2+ in the presence of the above-mentioned metals by masking with an excess of potassium or sodium cyanide. A small amount of iron may be masked by cyanide if it is first reduced to the iron(II) state by the addition of ascorbic acid. Titanium(IV), iron(III), and aluminium can be masked with triethanolamine mercury with iodide ions and aluminium, iron(III), titanium(lV), and tin(II) with ammonium fluoride (the cations of the alkaline-earth metals yield slightly soluble fluorides). 

Various initiation strategies and surfactant/cosurfactant systems have been used. Early work involved in situ alkoxyamine formation with either oil soluble (BPO) or water soluble initiators (persulfate) and traditional surfactant and hydrophobic cosurfactants. Later work established that preformed polymer could perform the role of the cosurfactant and surfactant-free systems with persulfate initiation were also developed, l90 222,2i3 Oil soluble (PS capped with TEMPO,221 111,224 PBA capped with 89) and water soluble alkoxyamines (110, sodium salt""4) have also been used as initiators. Addition of ascorbic acid, which reduces the nitroxide which exits the particles to the corresponding hydroxylamine, gave enhanced rates and improved conversions in miniemulsion polymerization with TEMPO.225 Ascorbic acid is localized in the aqueous phase by solubility. 

Prohexadione-calcium at the level of 0.08 mg kg in tap water degrades and disappears rapidly. Degradation of prohexadione-calcium can be prevented by addition of ascorbic acid at about 1 mg kg in tap water. Degradation products of prohexadione-calcium by aqueous chlorination are identified by mass spectrometry. 

Cyanide Addition of ascorbic acid, then render alkaline to pH 11-12 with sodium hydroxide This determinand must be preserved immediately. Need for separate container. Any residual chlorine must be removed with ascorbic acid. 

Shriadah et al. [516] determined molybdenum VI in seawater by densitometry after enrichment as the Tiron complex on a thin layer of anion exchange resin. There were no interferences from trace elements or major constituents of seawater, except for chromium and vanadium. These were reduced by the addition of ascorbic acid. The concentration of dissolved molybdenum (VI) determined in Japanese seawater was 11.5 pg/1, with a relative standard deviation of 1.1%. 

The situation with wholemeal flour is refreshingly simple. Flour treatments are banned and there are no statuary additions. The addition of ascorbic acid to wholemeal flour is forbidden but the use of ascorbic acid in wholemeal bread is allowed. Presumably, it was thought beneficial to allow the change so that the Chorleywood plants could make wholemeal bread. The ascorbic acid presumably goes in as an improver with other ingredients. 

A simple and economical method for recovering silver residues by dissolution in used photographic fixer (thiosulfate) solution, then precipitation by addition of zinc powder, is detailed [1]. After the acid digestion phase of silver recovery operations, addition of ammonia followed immediately by addition of ascorbic acid as reducant gives a near-quantitative recovery of silver metal, and avoids the possibility of formation of silver nitride [2],... 

Dissolve the required amount of peptide (1 mole peptide per about 50 moles of lysine residues of the carrier, e.g., 60 pmol of peptide per 5 mg ovalbumin) in PBS and mix with the activated carrier. Stir at RT for 1 h and block with 10 mg/ml of solid NaBH4 at RT for 20 min. Alternatively, reduce (block) the formed azome-thines (Schiff bases) to secondary amines by addition of ascorbic acid (final concentration 5 mM). 

When adrenaline was oxidized in the presence of Cu++ ions, the loss of the native catecholamine fluorescence was again detected, but in this case the initial oxidation products were also fluorescent. Addition of ascorbic acid did not increase the fluorescence. However, addition of ferricyanide ions destroyed the fluorescence, but it could be regenerated by the addition of ascorbic acid. Noradrenaline behaved somewhat differently in that the initial oxidation product had little fluorescence, probably due to the quenching effect of the Cu++ ions, since reduction of the Cu++ ion concentration increased... 

However, its presence is not the only determinant of whether or not oxidative deterioration occurs. Olson and Brown (1942) showed that washed cream (free of ascorbic acid) from susceptible milk did not develop an oxidized flavor when contaminated with copper and stored for three days. Subsequently, the addition of ascorbic acid to washed cream, even in the absence of added copper, was observed to promote the development of an oxidized flavor (Pont 1952). Krukovsky and Guthrie (1945) and Krukovsky (1961) reported that 0.1 ppm added copper did not promote oxidative flavors in milk or butter depleted of their Vitamin C content by quick and complete oxidation of ascorbic acid to dehydroascorbic acid. Krukovsky (1955) and Krukovsky and Guthrie (1945) further showed that the oxidative reaction in ascorbic acid-free milk could be initiated by the addition of ascorbic acid to such milk. Accordingly, these workers and others have concluded that ascorbic acid is an essential link in a chain of reactions resulting in the development of an oxidized flavor in fluid milk. 

AG Fogg, AM Summan. Further differential-pulse polarographic and visible spectrophotometric studies of the degradation of permitted synthetic food coloring matters without the addition of ascorbic acid accelerated heat degradation studies. Analyst 109(6) 743-747, 1984. 

Mycotoxins are toxic secondary metabolites produced by fungi growing within or on foods. They can be a serious threat to human and animal health (Nagler el al., 2001). Table 11.4 details mycotoxins associated with soft drinks and fruit juice manufacture and raw materials. Patulin is the most common mycotoxin associated with fruit juice, particular ly apple juice (Pitt Hocking, 1997). It commonly occurs if juice is produced from stored apples. Mould growth in infected apples increases with time, raising levels of patulin. The use of windfall apples for juice is also a factor. Avoidance of windfall apples, filtration of juice and pressing quickly after harvest are all methods to reduce the incidence of patulin in juice. Patulin can be destroyed by fermentation to cider or by the addition of ascorbic acid (Marth, 1992). Within Europe, the European Union has set a limit of 50 ig/kg for patulin in both apple juice and cider. A recent survey of apple products in Chile found that 28% of samples of juice and concentrate exceeded this limit (Canas Aranda, 1996). 

Figure 19. ESR spectrum (B) produced by the addition of ascorbic acid to the reaction mixture of glucose with X-butylamine (each 1 MJ in ethanol refluxed for 15 min. A reaction mixture. B reaction mixture (0.5 mL) kept at room temperature for 15 min after the addition of ascorbic acid (0.1 g/mL, 0.05 mL). (Reproduced with permission from Ref. 5.)...

It has been shown that incubation with L-dopa increased the level of GSH in neurons. The pure neuronal cultures were destroyed by incubation with L-dopa, whereas the addition of ascorbic acid or superoxide dismutase protected the cells. These results show that the upregulation of cellular GSH evoked by auto-oxidizable agents is associated with significant protection of cells. Glia play an essential role in the response of mesencephalic cell cultures. An ability to upregulate GSH may serve a protective role. 

Hahn, B., Grosch, W. 1998. Distribution of glutathione in Osborne fractions as affected by additions of ascorbic acid, reduces and oxidised glutathione. J Cereal Sci 27 117-125. 

The data given in Table VI show that there was a considerable increase in formation of tritiated water upon in vitro addition of ascorbic acid. Addition of ascorbic acid failed to increase tritiated water for mation with minces of normal granuloma, and no effect was observed... 

Table VI. Stimulation of Hydroxylation of Proline 4>y Ascorbic Acid-Deficient Granuloma by in Vitro Addition of Ascorbic Acid...

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