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Phosphate-buffered saline (PBS) is a buffer solution (pH ~ 7.4) commonly used in biological research. It is a water-based salt solution containing disodium hydrogen phosphate , sodium chloride and, in some formulations, potassium chloride and potassium dihydrogen phosphate .
Buffer capacity falls to 33% of the maximum value at pH = pK a ± 1, to 10% at pH = pK a ± 1.5 and to 1% at pH = pK a ± 2. For this reason the most useful range is approximately pK a ± 1. When choosing a buffer for use at a specific pH, it should have a pK a value as close as possible to that pH. [2]
McIlvaine buffer is a buffer solution composed of citric acid and disodium hydrogen phosphate, also known as citrate-phosphate buffer. It was introduced in 1921 by the United States agronomist Theodore Clinton McIlvaine (1875–1959) from West Virginia University , and it can be prepared in pH 2.2 to 8 by mixing two stock solutions.
The receipt uses a ratio of 10:2 (assuming anhydrous Na2HPO4) of Na2HPO4 to KH2PO4 - equal amounts of them should result in a solution with pH=pKa=7.2 - the 10:2 ratio ensures that the resulting solution is basic (pH 8 to 9) - so that the pH can indeed be adjusted with _HCl_ to 7.4. Diluting with ultrapure water would only shift this to a pH ...
The salt is known in anhydrous form as well as hydrates Na 2 HPO 4 ·nH 2 O, where n is 2, 7, 8, and 12. All are water-soluble white powders. The anhydrous salt is hygroscopic. [1] The pH of disodium hydrogen phosphate water solution is between 8.0 and 11.0, meaning it is moderately basic: HPO 2− 4 + H 2 O ⇌ H 2 PO − 4 + OH −
Hanks' salts is a collective group of salts rich in bicarbonate ions, formulated in 1940 by the microbiologist John H. Hanks. [1] Typically, they are used as a buffer system in cell culture media and aid in maintaining the optimum physiological pH (roughly 7.0–7.4) for cellular growth.
pK a: Because most biological reactions take place near-neutral pH between 6 and 8, ideal buffers would have pK a values in this region to provide maximum buffering capacity there. Solubility: For ease in handling and because biological systems are in aqueous systems, good solubility in water was required.
BSS (ophthalmic irrigation solution) (produced by Alcon) . Composition per 1 mL: sodium chloride (NaCl) 6.4 mg, potassium chloride (KCl) 0.75 mg, calcium chloride dihydrate (CaCl 2 ·2H 2 O) 0.48 mg, magnesium chloride hexahydrate (MgCl 2 •6H 2 O) 0.3 mg, sodium acetate trihydrate (C 2 H 3 NaO 2 ·3H 2 O) 3.9 mg, sodium citrate dihydrate (C 6 H 5 Na 3 O 7 ·2H 2 O) 1.7 mg, sodium hydroxide ...
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