Buffer action preparation

Buffer action 46 Buffer capacity 48 Buffer mixture universal, (T) 831 Buffer solutions 46, (T) 831 acetic acid-sodium acetate, 49 for EDTA titrations, 329 preparation of IUPAC standards, 569 Bumping of solutions 101 Buoyancy of air in weighing 77 Burette 84, 257 piston, 87 reader, 85 weight, 86... 

Biochemists and molecular biologists use phosphate buffers to match physiological conditions. A buffer solution that contains H2 PO4 as the weak acid and HP04 as the weak base has a pH value very close to 7.0. A biochemist prepares 0.250 L of a buffer solution that contains 0.225 M HP04 and 0.330 M H2 PO4. What is the pH of this buffer solution Is the buffering action of this solution destroyed by addition of 0.40 g NaOH ... 

Citrated blood is diluted 1 10 with enzyme buffer solution, and preservative is added (H19). The buffer is prepared by dissolving 0.2 g of Clarase (Fisher Scientific Co., New York) in 100 ml citrate buffer (5 g potassium citrate monohydrate and 1 g citric acid monohydrate in 1000 ml distilled water, pH 5.6). The solution is incubated for 3 days at 37°. After incubation, it is autoclaved 15 minutes to stop enzymatic action and coagulate proteins. It is filtered, and 1.0, 1.5, and 2.0 ml of the supernatant is added to individual flasks and assayed. Control flasks are included to estimate pantothenic acid contamination of the enzyme. 

Example 2,8b One liter of a buffered solution is prepared with 0.1 M acetic acid (AcH) + 0.2 M sodium acetate (AcNa). Plot fi vs. pH for the interval 0 < pH < 14. (See data from Example 2.8a, where this buffering action is further explained.)... 

Intermediate-acting insulins are either the neutral protamine Hagedorn insulin (NPH isophane insulin suspension) or the Lente insulin (insulin zinc suspension) the former is a suspension of the insulin-protamine-zinc complex in a phosphate buffer and the latter is a mixture of crystallized and amorphous insulin in acetate buffer. These preparations have an onset of action within about 2h, peak activity after about 4-12 h, and a duration of up to 24 h (Table 4). Commercially available mixtures of soluble insulins and isophane insulins have activities that would normally place them within the intermediate-acting category. Mixed insulin-zinc suspensions are sometimes classified as either intermediate- or long-acting as the duration of action may be up to 30 h. 

The Common Ion Effect and Buffer Solutions 19-2 Buffering Action 19-3 Preparation of Buffer Solutions 19-4 Acid-Base Indicators... 

The ratio of acid to salt should never exceed 100 or fall below 1/100, for then the buffer- action of these mixtures is lost. We may say quite generally that buffer mixtures, in which the pH lies between pHA — 1.7 and pHA + 1.7, can be prepared from a salt and its acid. 

Most buffer solutions are composed of a weak acid and one of its alkali salts. Usually such mixtures of an acid and its salt may be prepared to extend over a range of two pH units, between pK 1 and pK — 1 where pK is the negative logarithm of the dissociation constant Ka) of the acid. Buffer solutions made with acetic acid, which has a dissociation constant of 1.86 X 10 or a pK of 4.73, are useful in the pH range between 3.7 and 5.7. It should be recalled that the intensity of buffer action (buffer capacity) in a series of 0.7 buffer solutions is greatest in the mixture of pH equal to pK, in which the ratio of acid to salt is unity (cf. Fig. 13). The greater the difference between pH and pK, the less pronounced becomes the buffer action. A solution in which the acid to salt ratio exceeds 10 be stored unchanged. 

It is often preferable for physiological purposes to use buffer systems other than the boric acid-borate mixtures. L. Michaelis has found that mixtures of veronal (diethylbarbituric acid) with its sodium salt show a satisfactory buffer action in the neighborhood of pH = 8.0. Pure commercial samples of the sodium salt of veronal are readily available, and may be used frequently without previous recrystallization. Buffer mixtures can be prepared by adding hydrochloric acid to the salt. This compound is water-free, and should suffer no loss in weight when dried at 100°. A 0.1 N solution in water requires exactly an equivalent quantity of 0.1 N hydrochloric acid when neutralized against methyl red. A stock solution should contain 10.30 g. of the sodium salt per 500 c.c. Only carbon dioxide free water should be used. 

Stability of indicator mixtures. Mixtures of the two forms of an indicator show a pH variation with time of standing. It is advisable, therefore, to prepare new solutions every two or three days, especially when they are to be used for unbuffered solutions. The mixtures may be kept for fourteen days if the solution under investigation has even a very slight buffer action. 

In paints, zinc oxide serves as a mildewstat and acid buffer as well as a pigment. The oxide also is a starting material for many zinc chemicals. The oxide supphes zinc in animal feeds and is a fertilizer supplement used in zinc-deficient soils. Its chemical action in cosmetics (qv) and dmgs is varied and complex but, based upon its fungicidal activity, it promotes wound healing. It is also essential in nutrition. Zinc oxide is used to prepare dental cements in combination with eugenol and phosphoric and poly(acrylic acid)s (48) (see Dental materials). 

An amount of enzyme preparation equivalent to 900 mg of wet cells was made up to 25 ml with the above potassium phosphate buffer solution. 150 mg (1.15 mmol) of 5-fluorouracil and 1.0 gram of thymidine (4.12 mmol) were dissolved in 15 ml of the above potassium phosphate buffer solution. The mixture was incubated at 37°C for 18 hours. After this time, enzyme action was stopped by the addition of four volumes of acetone and one volume of peroxide-free diethyl ether. The precipitated solids were removed by filtration, and the filtrate was evaporated under nitrogen at reduced pressure until substantially all volatile organic solvent had been removed. About 20 ml of aqueous solution, essentially free of organic solvent, remained. This solution was diluted to 100 ml with distilled water. 

This is a crystalline product of insulin and an alkaline protein where the protein/insulin ratio is called the isophane ratio. This product gives a delayed and uniform insulin action with a reduction in the number of insulin doses necessary per day. Such a preparation may be made as follows 1.6 g of zinc-insulin crystals containing 0.4% of zinc are dissolved in 400 ml of water, with the aid of 25 ml of 0.1 N hydrochloric acid. To this are added aqueous solutions of 3 ml of tricresol, 7.6 g of sodium chloride, and sufficient sodium phosphate buffer that the final concentration is As molar and the pH is 6.9. 

A confluent monolayer of Madin-Darby canine kidney (MDCK) cells was grown in 96-well plates. Serial tenfold dilutions in minimal essential medium were prepared from the aliquots of allantoic fluid taken from the irradiated specimen. These dilutions were applied to MDCK cells and incubated for 48 h at 36 °C in 5% C02. The cells were then washed two times for 5 min with phosphate buffered saline (PBS) and incubated for 1 h with 100 pi of 0.5 mg/ml solution of 3-(4,5-dimethyl-thiazolyl-2) 2,5-diphenyltetrazolium bromide (MTT, ICN Biochemicals Inc., Aurora, Ohio). After lh, the colored deposit was dissolved in 100 pi DMSO, and optical density in the wells was measured on plate reader Victor 1420 (Perkin Elmer, Finland). Based on the data obtained, the infectious titer of the vims was determined as a decimal logarithm of reciprocal to the dilution of the specimen causing destruction of 50% of cells. The inhibiting action of irradiation was evaluated by decreasing the vims titer. 

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