Ascorbic acid solution preparation

Azomethine-H reagent - Dissolve 0.45 g of azomethine-H in 100 ml of 1 % m/v L-ascorbic acid solution. Prepare fresh weekly and store in a refrigerator. 

Solutions. Solutions of ferrlcyanlde (Baker Chemical Co., Phllllpsburg, NJ) were prepared In 1.0 M KCl (Mallnckrodt, Paris, KY). Ascorbic acid solutions were prepared In 0.1 H phosphate buffer adjusted to pH 2.0. All solutions were prepared with triple distilled water. Solution preparation precautions have been previously described (15). 

Apples (Red Belle de Boskoop, Jonagold or Mutzu) were cut and milled (1.5 mm) and 5% (w/w) of a 2% ascorbic acid solution was added immediately. Enzyme preparations (25 mg enzyme protein / kg mash) were added and the mash was incubated for 2 hours at 20°C whereafter it was pressed. The resulting apple juice was pasteurised at 85°C to discontinue further enzyme degradation. The cloud was measured as turbidity in EF/F units [15]. The cloud stability was determined by a centrifugation test as the amount of turbidity remaining after centrifugation at 4,200 x g for 15 minutes [15]. 

Ascorbic acid solution. Weigh 2.7 g of ascorbic acid into a 250-mL Erlenmeyer flask, dilute to 100 mL with distilled water, and swirl to make homogeneous. Prepare just prior to the run. 

For phloroglucinolysis, a solution of 0.1 N HCl in MeOH, containing 50 g/L phloroglucinol and 10 g/L ascorbic acid, is prepared. The PA of interest is reacted in this solution at 50°C for 20 min and then combined with 5 volumes of 40 mM aqueous sodium acetate to stop the reaction. After acid-catalyzed cleavage in the presence of phloroglucinol, the fraction is depolymerized and the terminal subunits released as flavan-3-ol monomers and the extension subunits released as phloroglucinol adducts of flavan-3-ol intermediates. These products are then separated and quantified by HPLC [25]. 

Ascorbic acid solution, 1.5% m/v - prepare immediately before use, allowing 5 ml per standard, blank and sample, with some spare for any repeats. 

M ascorbic acid solution dissolve 0.88 g ascorbic acid (vitamin C) in water and bring it to 50 mL volume. This must be prepared fresh every week and stored at 4°C. 

Reagent C Mix 3 volumes of 1 M Sulfuric Acid with 1 volume of Ammonium Molybdate Solution, then add 1 volume of Ascorbic Acid Solution, and mix well. Prepare fresh daily. 

Ascorbic acid solution for tin determination, 5% m/v Prepare fresh weekly. 

Prepare reagent A by mixing thoroughly 1 volume (10 ml) 6N sulfuric acid with 2 volumes (20 ml) distilled water, 1 volume (10 ml) ammonium molybdate solution, and finally 1 volume (10 ml) ascorbic acid solution. This reagent should be prepared fresh each day because it is quite unstable. 

Oxidation is a common problem associated with some organic acids, for example, ascorbic acid (vitamin C). When dissolved, ascorbic acid is readily oxidized to dehydroascorbic acid, catalyzed by air or light exposure (Wu et al., 1995). Ascorbic acid solutions should be freshly prepared and kept tightly closed and not exposed to light. Organic acids also promote lipid oxidation which increases with increasing acid concentration (Ogden et al., 1995). 

The radiolabelled preparations were stored at room temperature in 0.4M sodium acetate or 0.3M ascorbic acid solution up to 72 h post-labelling for Lu-DOTATATE and up to 36 h post-labelling for " Y-DOTATATE, The influence of the radioactive concentration of the stored preparation on its stability was investigated using solutions of various radioactive concentrations 1.0, 20 and 50 mCi/mL for Y-DOTATATE. and 1.0, 15 and 35 mCi/mL for Lu-DOTATATE. The stability of the preparations (described as the radiochemical purity) was determined by HPLC and SepPak separation. 

These methods are limited by the air-flow rate (especially for midget impingers), and also the aqueous solutions are not a very convenient sampling medium, particularly for held experiments. Sample recovery problems are often encountered in liquid-liquid extraction due to the aqueous buffers or to the emulsion formation. Labor-intensive sample preparation procedures and the relatively fast degradation of the aqueous ascorbic acid solution are the two additional drawbacks when using this sampling method. 

Beside the estimation of medium microviscosity, quartz plates modified by BFLl were used for the quantitative analysis of ascorbate. For this purpose, a number of solutions of ascorbic acid were prepared with different concentrations, and the kinetics of change in steady-state fluorescence was recorded. There are two parallel processes that influence fluorescence (a) trans-cis photoisomerization and (b) reduction of the nitroxide moiety in traws-BFLl. After a correction taking into account the influence of trans-cis photoisomerization (curve b ), the pseudo-first-order kinetics of BFL reduction appears as curve c. The correction was done by performing a parallel measurement under identical conditions but without adding ascorbate. 

Ascorbic acid solution for AAU 10 mg of ascorbic acid powder was dissolved in glass distilled water, which was previously boiled, cooled and saturated with CO2. The volume of the solution was made upto 100 ml and stored in an amber coloured bottle at 3 to 5 C, till used. This solution was also freshly prepared daily. 

Standard Curve Ascorbic acid solutions of concentrations ranging from 0.01 to 0.09 mg/ml were prepared from a stock solution by diluting with cold, CO2 - saturated glass distilled water to the requisite concentration. 

Prepare a standard as follows Pipet 10 ml. of a 1 milligram per cent standard ascorbic acid solution into a 50 ml. volumetric flask. Make up to volume with 5% trichloroacetic acid. Mix thoroughly. Pipet 30 mm. of this solution into a 6 x 50 mm. tube. 

Description of some of the hydrotropes used in the solubilization of riboflavin will illustrate the diversity of compounds employed. Nicotinamide increases the solubility of riboflavin in polar liquids [290], and it has been observed [291] that ascorbic acid also has a hydrotropic effect on riboflavin. A 20 % aqueous ascorbic acid solution increases the aqueous solubility of riboflavin at room temperature by 4.5 times. This is important in the formulation of multi-vitamin preparations. Concentrated solutions of (—) —, or (+) — tryptophan dissolve riboflavin to the extent of 4 mg ml at pH 6.8, and the addition of nicotinamide markedly increases the solubility, giving stable solutions, suitable for injection [292]. N-(2-hydroxyethyl) gentisamide may also be employed as solubilizer [293], as can... 

Prepare the indicator solution by making a 0 08 per cent solution of 2,6-dichlorophenolindophenol in copper-free water, filter and keep in the dark. The strength diminishes more rapidly in daylight after some time it gives a solution which during titration deposits a bluish precipitate and interferes with the end-point, it must then be discarded. The dye solution should be standardised at least daily and preferably just before use against freshly prepared ascorbic acid solution (50 mg/100 ml in 20 per cent metaphosphoric acid) which in turn has been standardised against 0 01 N iodine. 

Ascorbic Acid Solution - Dissolve 1 g of ascorbic acid, CgHgOg, in 50 ml water. Prepare fresh daily. 

Mixed Reagent - Add successively with a graduated cylinder and mix after each addition 50 ml sulphuric acid (6.5), 15 ml ammonium molybdate solution (6.3), 30 ml ascorbic acid solution (6.2) and 5 ml potassium antimonyl tartrate solution (6.4). Prepare fresh daily. 

Ascorbic acid, HQHyOs, also known as vitamin C, is a weak acid. It is an essential vitamin and an antioxidant. A solution of ascorbic acid is prepared by dissolving 2.00 g in enough water to make 100.0 mL of solution. The resulting solution has a pH of 2.54. What is for ascorbic acid ... 

Ascorbic acid is a powerful reductant and reacts with different oxidants by 2,4 or even 6 electron changes. It is important to establish the stoichiometry of its reaction with Mn(lII) sulphate solution. However since ascorbic acid solutions are oxidised in air, its solutions should be freshly prepared in boiled-out water and freshly used. 

Prepare 0.025 M L ascorbic acid solution by weighing accurately about 1.1 g of the purest solid, dissolving it and making up the solution in a 250 cm volumetric flask using boiled-out distilled deionised water. Pipette 10 cm of the solution into a conical flask, acidify with dilute sulphuric acid and add a few drops of N-phenylanthranilic acid indicator. Titrate with standardised freshly prepared Mn(lll) sulphate solution (as above) until the colour changes sharply to violet. Repeat to obtain concordant results and calculate, from the average titre, the ascorbic acid Mn(llI) molar ratio. 

The excess of ascorbic acid solution, after reacting with the complex and the percentage of Mn(III) in your preparation and hence its % purity. 

Weigh out accurately about O.S g of your preparation, dissolve in known excess of 0.1 M ascorbic acid solution and back titrate the excess with standardised Mn solution as in Sec. 12.4.1. 

Alternatively add to the weighed solid a known excess of standard freshly prepared ascorbic acid solution. Ensure that more ascorbic acid solution is added after the complete solubility of the solid, recording the volume used. Back titrate the excess against standardised Mn(lll) solution. Calculate the percentage purity. 

This complex is obtained by the oxidation of Mn(III) by permanganate in presence of the ligand. It can be analysed by dissolving in a known excess of fireshly prepared standard ascorbic acid solution and back titrating the excess with Mn(IIl) sulphate solution. 

Repeat one of the runs, say that at 20 C using ascorbic acid solution freshly prepared in boiled-out 0.01 M HCl and comment on the effect of the acid on the rate of reaction. 

Ascorbic acid solution, freshly prepared and standardised, will reduce Ni(III) to Ni(II), the excess ascorbic acid can be back titrated with any suitable oxidant eg Mn(III) sulphate. 

Weigh out accurately about 0.4 g of your preparation, previously finely ground. Add a known excess of standard ascorbic acid solution (SO cm of 0.028 M solution, fireshly prepared in boiled-out distilled water). The solid should dissolve completely, when Ni(II) is formed in solution. Titrate the excess ascorbic acid against standardised Mn2(S04)3 solution (Sec. 12.4.1) using N-phenylanthranilic acid as indicator. The end point is indicated by a sudden change to violet colour. Repeat the determination and calculate the percentage Ni in your sample and hence the percentage purity of your preparation. 

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