pKa
Definition
The negative logarithm of the acid dissociation constant. For a basic drug it is the pH at which half the molecules are protonated and half are free base. For an acidic drug it is the pH at which half are protonated (HA) and half are deprotonated (A minus). Partition into organic solvent is favoured when the drug is in its un-ionised form.
Related terms
- Acid Fraction
- The organic phase recovered when the biological aqueous is acidified to pH 2 to 3 and shaken with diethyl ether or chloroform....
- Alkaline Fraction
- The organic phase recovered when the aqueous is basified to pH 9 to 10 with ammonium hydroxide or sodium hydroxide and shaken...
- Cut-Off
- The minimum analyte concentration that an SFSL reports as positive. SAMHSA-style serum cut-offs commonly used at Indian labs include morphine 2 ng/mL,...
- DFC
- Drug-facilitated crime, the umbrella term for sexual assault, robbery or kidnapping in which a victim has been incapacitated by a clandestinely administered...
- Neutral Fraction
- The organic phase recovered when the aqueous is buffered to pH 7 to 9 and extracted with a less polar solvent like...
- Post-Mortem Redistribution
- The movement of drugs from solid tissues into central blood after death, due to diffusion along concentration gradients, autolytic enzyme release, and...
Explained in
- Acidic, Neutral and Alkaline Drug AnalysisThe negative logarithm of the acid dissociation constant. For a basic drug it is the pH at which half the molecules are protonated and half are free base. For...