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Lidstrom:Buffers: Difference between revisions
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→phosphate buffer
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*pH rane: 5.8-8 | *pH rane: 5.8-8 | ||
* Phosphate buffering is based on the fact that phosphate can be in four states based on the pH. | * Phosphate buffering is based on the fact that phosphate can be in four states based on the pH. | ||
** [[image:2014_02_09 phosphate states]] | ** [[image:2014_02_09 phosphate states.png]] | ||
** It will shift between the different levels of protonation based on how many protons are available in solution. Thus it can be a source/sink for protons. Like all (good) buffers, if more H+ ions show up in solution, it can help absorb these and maintain the initial pH. Converseley, it can release H+ ions when they disappear from solution. | ** It will shift between the different levels of protonation based on how many protons are available in solution. Thus it can be a source/sink for protons. Like all (good) buffers, if more H+ ions show up in solution, it can help absorb these and maintain the initial pH. Converseley, it can release H+ ions when they disappear from solution. | ||
*Aqueous phosphate exists in four forms. In strongly basic conditions, the phosphate ion (PO<sub>4</sub><sup>3−</sup>) predominates, whereas in weakly basic conditions, the hydrogen phosphate ion (HPO<sub>4</sub><sup>2−</sup>) is prevalent. In weakly acid conditions, the dihydrogen phosphate ion (H2PO<sub>4</sub><sup>−</sup>) is most common. In strongly acidic conditions, trihydrogen phosphate (H<sup>3</sup>PO<sub>4</sub>) is the main form. | *Aqueous phosphate exists in four forms. In strongly basic conditions, the phosphate ion (PO<sub>4</sub><sup>3−</sup>) predominates, whereas in weakly basic conditions, the hydrogen phosphate ion (HPO<sub>4</sub><sup>2−</sup>) is prevalent. In weakly acid conditions, the dihydrogen phosphate ion (H2PO<sub>4</sub><sup>−</sup>) is most common. In strongly acidic conditions, trihydrogen phosphate (H<sup>3</sup>PO<sub>4</sub>) is the main form. | ||
