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For example, the acid may be acetic acid and the salt may be sodium acetate. The Henderson–Hasselbalch equation relates the pH of a solution containing a mixture of the two components to the acid dissociation constant, K a of the acid, and the concentrations of the species in solution. [6]
As calculated by the Henderson–Hasselbalch equation, in order to maintain a normal pH of 7.4 in the blood (whereby the pK a of carbonic acid is 6.1 at physiological temperature), a 20:1 ratio of bicarbonate to carbonic acid must constantly be maintained; this homeostasis is mainly mediated by pH sensors in the medulla oblongata of the brain ...
The charge of a molecule depends upon the pH of its solution. In an acidic medium, basic drugs are more charged and acidic drugs are less charged. The converse is true in a basic medium. For example, Naproxen is a non-steroidal anti-inflammatory drug that is a weak acid (its pKa value is 5.0). The gastric juice has a pH of 2.0. It is a three ...
Speciation of ions refers to the changing concentration of varying forms of an ion as the pH of the solution changes. [1]The ratio of acid, AH and conjugate base, A −, concentrations varies as the difference between the pH and the pK a varies, in accordance with the Henderson-Hasselbalch equation.
The Henderson-Hasselbalch equation offers a way to determine the proportion of a substance that is ionized at a given pH. In the stomach, drugs that are weak acids (such as aspirin ) will be present mainly in their non-ionic form, and weak bases will be in their ionic form.
The Henderson-Hasselbalch equation is useful for calculating blood pH, because blood is a buffer solution. In the clinical setting, this equation is usually used to calculate HCO 3 from measurements of pH and PaCO2 in arterial blood gases. The amount of metabolic acid accumulating can also be quantitated by using buffer base deviation, a ...
Finally, using the Henderson-Hasselbalch equation, and knowing the drug's (pH at which there is an equilibrium between its ionized and non-ionized molecules), it is possible to calculate the non-ionized concentration of the drug and therefore the concentration that will be subject to absorption:
Thus, in an aqueous solution at pH about 7, typical of biological systems, the Henderson–Hasselbalch equation indicates they exist predominantly as dicarboxylate anions. The dicarboxylic acids, especially the small and linear ones, can be used as crosslinking reagents. [27]