API | Intermediates Assay, Potency & Purity

Introduction
Assay:
Definition
Calculation
Potency:
Definition
Calculation
Purity:
Definition
Calculation

1. API | Intermediates Assay, Potency & Purity

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, % impurity present is = 0.3 % Residual solvent is = 100 ppm or 0.01 % Sulfated ash is = 0.2 % Heavy Metal = 10 ppm or 0.001 % LOD or Water content is = 2 % and  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

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