The document details the critical concepts of assay, potency, and purity in the pharmaceutical industry, emphasizing their importance for ensuring drug quality. It defines each term and provides methods for calculating assay, potency, and purity based on quantitative analyses, including formulas and example calculations. Understanding these concepts is crucial for producing high-quality, life-saving drugs.

2. Contents:-
•Introduction
•Assay:
Definition
Calculation
•Potency:
Definition
Calculation
•Purity:
Definition
Calculation

3. Introduction:
• Pharmaceutical industry is quality oriented
industry that requires high accuracy in while
producing drug hence the assay or potency or
purity of Drug sample is a key factor to confirm
the quality of the drug.
• Pharmaceutical industry producing life saving
drugs due to that it is important to understand
difference between assay potency and purity of
the drug.

4. Assay:
Definition:
An analytic procedure in laboratory for quantitative
assessing or measuring the presence or amount of a target
entity.
In the pharmaceutical industry, an assay is the main test for
any drug Substance / product.
As there is multiple tests for the drug product but the assay
is a test that gives proper information of drug content
percentage.

5. Assay:
Calculation:
Three different ways:
 Assay on as is basis,
 Assay on dried basis and
 Assay on anhydrous basis.

6. Assay Calculation:
Assay On As Is Basis:

7. Assay Calculation:
Assay On As Is Basis:

8. Assay Calculation:
Assay On Dry Basis:

9. Assay Calculation:
Assay On Dry Basis:

10. Assay Calculation:
Assay On Anhydrous Basis:

11. Assay Calculation:
Assay On Anhydrous Basis:

12. Potency:
Definition:
Potency is a measure of drug activity expressed in terms of
the amount required to produce an effect of given intensity.
A highly potent drug evokes a given response at low
concentrations, while a drug of lower potency evokes the
same response only at higher concentrations.

13. Potency Calculation:
Potency can be calculated by eliminating % of impurity,
heavy metal, sulfated ash, residual solvent and LOD or
Water content from the targeted drug.
For Example:
Potency = [100 – (moisture or LOD + residual solvents +
heavy metals + sulphated ash + impurities)]

14. Potency Calculation:
Suppose For Example,
A. % impurity present is = 0.3 %
B. Residual solvent is = 100 ppm or 0.01 %
C. Sulfated ash is = 0.2 %
D. Heavy Metal = 10 ppm or 0.001 %
E. LOD or Water content is = 2 % and
F. Target value of assay is = 100 %
So, by applying value in formula,
Potency = [100-( 0.3+0.01+0.2+0.001+2)]
= 100 – 2.511
= 97.489 %
• This will be the potency of the drug after eliminating all impurities.

15. Purity:
Definition:
Purity of the drug is determined by the area
normalization method.
It is directly calculated by Chromatographic system
and found on the chromatograms obtained from the
HPLC / GC system.

16. Purity Calculation:
% Purity = (Area of desired peak) X 100
Sum of area of all peaks

17. Purity Calculation:
Suppose,
Area of Drug peak in chromatogram = 1000,
Sum of area of all peaks = 500000
Then the calculated value will be as follow:
% Purity = 1000 X 100
500000
= 0.2%
= 100-0.2
= 99.8%
% Purity = (Area of desired peak) X 100
Sum of area of all peaks