Difference Between Purity and Potency


Purity refers to the degree to which a substance is free from impurities or contaminants. In pharmaceuticals and chemicals, purity is a critical parameter because impurities can affect the safety, efficacy and stability of the final product. Purity is usually expressed as a percentage and can be determined through various analytical techniques such as chromatography (e.g., HPLC, GC), spectroscopy (e.g., UV-Vis, FTIR), or elemental analysis.

If a pharmaceutical drug is said to be 99% pure, it means that 99% of the substance is the active ingredient, and the remaining 1% consists of impurities or other components.


Potency, on the other hand, refers to the strength or effectiveness of a substance in producing a specific biological or pharmacological effect. In pharmaceuticals, potency is directly related to the concentration of the active ingredient(s) responsible for the desired therapeutic effect. It indicates how much of the active ingredient is present and active in a given formulation.

Potency is typically expressed as a measurement relative to a standard or reference substance. A drug with 100% potency contains the full amount of active ingredient required for its intended therapeutic effect. If the potency is less than 100%, it means that the drug contains a lower concentration of the active ingredient and may require a higher dose to achieve the desired effect.

In summary

Purity focuses on the cleanliness and freedom from impurities of a substance.

Potency focuses on the strength and effectiveness of the active ingredient in producing the desired biological or pharmacological effect.

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Resource Person: Jairus Fernandes

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