Solutions ascorbic acid

Keep under C02 protection at all times. Avoid contact with iron. Use stainless steel or glass-lined equipment only. Propylene glycol must be water white. 

Load 86.8 g propylene glycol into a glass-lined or suitable stainless steel-jacketed tank. 

Bubble C02 gas into the propylene glycol from the bottom of the tank. 

Add and dissolve the ascorbic acid into the propylene glycol with a minimum of stirring under C02 protection. 

When the ascorbic acid is in solution, immediately cool to approximately 25°C while continu- 

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In order to concentrate the lead extract, remove the lead from the organic solvent by shaking this with three successive 10 mL portions of the dilute hydrochloric acid solution, collecting the aqueous extracts in a 250 mL beaker. To the combined extracts add 5 mL of 20 per cent ascorbic acid solution and adjust to pH 4 by the addition of concentrated ammonia solution. Place the beaker in a fume cupboard, add 3 mL of the 50 per cent potassium cyanide solution and immediately adjust the pH to 9-10 with concentrated ammonia solution. Transfer the solution to a 250 mL separatory funnel with the aid of a little de-ionised water, add 5 mL of the 2 per cent NaDDC reagent, allow to stand for one minute and then add 10 mL of methyl iso butyl ketone. Shake for one minute and then separate and collect the organic phase, filtering it through a fluted filter paper. This solution now contains the lead and is ready for the absorption measurement. 

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]. 

Figure 2.5. Analytical manifolds for the determination of phosphate by flow injection analysis (a) and reverse flow injection (b). The symbols S, M, and A are the seawater, mixed reagent, and the ascorbic acid solutions. The pump injection valve and detector are represented by P, I, and D, respectively. W = waste. From [177]... 

Tominaga et al. [682,683] studied the effect of ascorbic acid on the response of these metals in seawater obtained by graphite-furnace atomic absorption spectrometry from standpoint of variation of peak times and the sensitivity. Matrix interferences from seawater in the determination of lead, magnesium, vanadium, and molybdenum were suppressed by addition of 10% (w/v) ascorbic acid solution to the sample in the furnace. Matrix effects on the determination of cobalt and copper could not be removed in this way. These workers propose a direct method for the determination of lead, manganese, vanadium, and molybdenum in seawater. 

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. 

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. 

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. 

Dissolve dyes in 3 mL water. Rinse the container with 2 mL water. Mix dye solution with ascorbic acid solution. Add this to the main bulk with stirring. 

Serum (400 pi) is thawed immediately before measurement and mixed with 600 pi ice-cold 28 pmol/1 ascorbic acid solution to protect against oxidation. After activation of the Sep-Pak Cl8 cartridge (Waters Chromatography) with 2 ml methanol and 10 ml of 14 pmol/1 ascorbic acid solution, the mixture is applied. The cartridge is washed with 3 ml of 14 pmol/1 ascorbic acid solution, and 5MTHF is eluted with... 

Ascorbic acid solutions, 28 pmol/1 and 14 pmol/1 dissolve 5 mg of ascorbic acid in 1 ml of water. Dissolve 1 1000 for 28 pmol/1 ascorbic acid solution and 1 2000 for 14 pmol/1 ascorbic acid solution store on ice. 

B. Measurement of Vitamin C Standard Ascorbic Acid Solution... 

As an example, Fig. 8.14 presents typical EPR spectra at 77 K of the Degussa P25 particles after different time of incubation in 0.65 M ascorbic acid solution [215], EPR analysis indicates the presence of at least two distinct V4+ species the sharp signals, overlapping with a broad single line of the aggregated V4+ centers. Similar spectra were observed in [48, 160, 163], etc. 

Fig. 8.16. Total amount of V4 ions [V4 ] on the surface of Ti02 Hombicat-100 (1), Degussa P25 (2), and Zr02 (3) nanoparticles at different time of incubation in the 0.65 M ascorbic acid solution.

Add 0.5 mL of an ascorbic acid solution and mix the contents thoroughly. Wait 20 min. for the development of the purple color. Record your observations on the Report Sheet. While you wait, you can perform the rest of the colorimetric tests. 

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. 

In a next step, 50 pL of an ascorbic acid solution (200 mg/mL) were added and the resulting mixture was mixed for 1 minute... 

Ascorbic Acid Solution Dissolve 10 g of ascorbic acid in water, and dilute to 100 mL. Store under refrigeration. The solution is stable for 7 days. 

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. 

Figure 65. Truth tables for the logic gates using a FIA cell containing a TRPyP modified electrode, and FIA signals (a) for consecutive injections of O.lOmM [Fe(CN)6]" monitored at 0.8 V and (b) for sequential injections of 0.10-mM [Fe(CN)6]" and 0.10-mM ascorbic acid solutions. The dashed lines indicate the potential applied to the electrode.

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. 

In Fig.6 we can see that the damping constant g2 of the L-xylo and the D-arabo ascorbic acid solutions become different with increasing concentration. Since the damping constant characterizes the distribution of mode frequencies in the present system, the effect of the D-arabo ascorbic acid on water structure is larger than that of the L-xylo ascorbic acid. 

As for the ascorbic acid solutions the effect on the dynamical structure of water is different between the isomerism. The effect of L-xylo ascorbic acid (Vitamin C) on the dyiiamical structure of water is less than that of D-arabo ascorbic acid which has little biological activity. It is interesting if this different effect on the dynamical structure of water may relate with a biological activity. 

Thiourea and dl-methionine are effective photoprotective agents for solutions of riboflavin (69), tetracycline hydrochloride (71), doxorubicin hydrochloride (77), reserpine (106), and potassium iodide (121). Thiourea enhances the photostability of solutions of minoxidil (48) and furosemide solution (74). Dl-methionine increases the photostability of ascorbic acid solutions (122). 

Asker AF, Canady D, Cobb C. Influence of dl-methionine on the photostability of ascorbic acid solutions. Drug Dev Ind Pharm 1985 11(12) 2109-2125. 

Some studies have shown that photoprotection does not affect the rate of decomposition significantly (87,88). A 50mg/mL ascorbic acid solution has been reported to be stable for up to 2.16mluxhours (59). 

In powder form, ascorbic acid is relatively stable in air. In tbe absence of oxygen and other oxidizing agents it is also heat stable. Ascorbic acid is unstable in solution, especially alkaline solution, readily undergoing oxidation on exposure to the air. The oxidation process is accelerated by light and heat and is catalyzed by traces of copper and iron. Ascorbic acid solutions exhibit maximum stability at about pH 5.4. Solutions may be sterilized by filtration. 

Radiolysis of oxygenated water or photolysis of hydrogen peroxide solutions yields two oxidative species, the -OH radical and the perhy-droxyl radical (HO2 02" + H ). As previously discussed, the final reaction product of hydroxyl radicals interaction with ascorbate above pH 6 is predominantly the ascorbate anion radical (A ). To account for the stoichiometry of ascorbic acid consumption in a Co gamma ray study of oxygenated ascorbic acid solutions, the ascorbic acid free radical was thought (3) to react with molecular oxygen to yield a transient adduct ... 

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