Phosphate buffers solubility

The release of thioridazine from the microspheres was determined by placing a sample containing the equivalent of 5 mg thioridazine in 1 L of pH 7.4 phosphate buffer (solubility, 23 mg/L). The mixture was maintained at 37°C with stirring at 300 rpm. Aliquots were withdrawn at various time points and assayed by measuring at the X for thioridazine, 265 nm, with a Cary Model 14 spectrophotometer. 

Description of Method. The water-soluble vitamins Bi (thiamine hydrochloride), B2 (riboflavin), B3 (niacinamide), and Be (pyridoxine hydrochloride) may be determined by CZE using a pH 9 sodium tetraborate/sodlum dIhydrogen phosphate buffer or by MEKC using the same buffer with the addition of sodium dodecyl-sulfate. Detection Is by UV absorption at 200 nm. An Internal standard of o-ethoxybenzamide Is used to standardize the method. 

S-Acetylthiocholine iodide [1866-15-5] M 289.2, m 203-204°, 204°, 204-205°. Recrystd from propan-l-ol (or wo-PrOH, or EtOH/Et20) until almost colourless and dried in a vacuum desiccator over P2O5. Solubility in H2O is 1% w/v. A 0.075M (21.7mg/mL) solution in O.IM phosphate buffer pH 8.0 is stable for 10-15 days if kept refrigerated. Store away from light. It is available as a 1% soln in H2O. [Biochemical Pharmacology 7, 88 I96I IR Hansen Acta Chem Scand 13 151 1959, 11 537 1957 Clin Chim Acta 2 316 7957 Zh Obshch Khim 22 267 1952.]... 

The choline ester is prepared by treating the 2-bromoethyl ester with trimethyl-amine. The ester is cleaved with butyrylcholine esterase (pH 6, 0.05 M phosphate buffer, rt, 50-95% yield). As with the morpholinoethyl ester, the choline ester imparts greater solubility to the C-terminal end of very hydrophobic peptides, thus improving the ability to cleave enzymatically the C-terminal ester. ... 

To circumvent these difficulties, a preparation of water-soluble coelenterazine has been developed (Teranishi and Shimomura, 1997a). The preparation contains coelenterazine and 50-times (by weight) of hydroxypropyl-P-cyclodextrin. To prepare this material, 0.1 ml of 3.0 mM coelenterazine in methanol and 0.2 ml of 45 mM solution of the cyclodextrin are mixed and dried under reduced pressure. The dried residue is extracted with 1.0 ml of lOmM phosphate buffer, pH 7.0, containing 2 mM EDTA (if needed), and the extract (after centrifugation) is again dried under reduced pressure. With this preparation, an aqueous solution containing up to 3 mM coelenterazine can be made. 

In the Phadebas TM amylase test (72) (Pharmacia Labs) the substrate was a water insoluble cross-TTnked blue starch in tablet form which also contains some inert ingredients, sodium and potassium phosphate buffer salts and sodium chloride. This polymer was hydrolyzed by amylase into water soluble blue starch fragments. After centrifugation the absorbance of the blue supernatant was proportional to the activity of amylase present in the test samples. The day to day variation on a quality control serum had a coefficient of variation of 2.7% based on 30 days of data in our laboratory. The method is simple, reproducible and uses microquantities of serum. 

The carboxylafion of indole into indole-3-carboxylate was observed by the purified indole-3-carboxylate decarboxylase as well as by the whole cells. For the carboxylafion reaction, temperatures over 30°C were not appropriate. The activities at 10, 20, and 30°C were about the same. The activity was maximal at pH 8.0 (Tris-HCl buffer, 100 mM). As shown in Fig. 10, the resting cells of A. nicotianae F11612 also catalyzed the carboxylafion of indole efficiently in the reaction mixture containing 20 mM indole, 3M KHCO3, 100mM potassium phosphate buffer (pH 6.0) in a tightly closed reaction vessel. By 6h, 6.81 mM indole-3-carboxylic acid accumulated in the reaction mixture with a molar conversion yield of 34%. Compared to the carhoxylation of pyrrole by pyrrole-2-carboxylate decarboxylase, the lower value compared might derive from the lower solubility of indole in the reaction mixture. 

Certain solubility factors are to be considered in work with periodate at different pH values. Above pH 5, disodium paraperiodate (Na2HJ06) tends to crystallize from aqueous solutions.246 Below pH 5, the sodium salt of periodic acid is more soluble, whereas above pH 5, the potassium salt is best employed. Phosphate-buffer solutions cause erroneous results,23 69a 60 61 and should be avoided in oxidations of carbohydrates. 

Solution of aniline blue 0.005% or 0.01% of water-soluble stain in phosphate buffer, pH 9.5. 

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