In a combination drug product related substances test we are generating impurity profile.
two claim is there:-
1. 100 mg
2. 5 mg
Now on the calculation of unknow impurity we are calculating the profile against lower claim of drug.
Kindly suggest is there any reference guideline that can justify the action.
Dilip Sharma
Calculating impurities in related substances involves determining the percentage of impurities present in a sample. Here's a step-by-step guide:
Chromatographic Methods (e.g., HPLC, GC)
1. Inject a sample into the chromatograph.
2. Separate the impurities from the main compound.
3. Integrate the peak areas for each impurity and the main compound.
4. Calculate the percentage of each impurity:
% Impurity = (Peak Area of Impurity / Total Peak Area) × 100
Calculations
1. Identify the main compound and impurities.
2. Determine the peak areas for each impurity and the main compound.
3. Calculate the percentage of each impurity:
% Impurity 1 = (Peak Area of Impurity 1 / Total Peak Area) × 100
% Impurity 2 = (Peak Area of Impurity 2 / Total Peak Area) × 100
...
% Impurity n = (Peak Area of Impurity n / Total Peak Area) × 100
Total Impurity Content
1. Sum the percentages of all impurities:
Total Impurity Content = % Impurity 1 + % Impurity 2 + ... + % Impurity n
Reporting
1. Report the percentage of each impurity.
2. Report the total impurity content.
Example
HPLC chromatogram:
Peak Area of Main Compound = 1000 mAU
Peak Area of Impurity 1 = 20 mAU
Peak Area of Impurity 2 = 15 mAU
Calculations:
% Impurity 1 = (20 / 1035) × 100 = 1.93%
% Impurity 2 = (15 / 1035) × 100 = 1.45%
Total Impurity Content = 1.93 + 1.45 = 3.38%
Report:
Impurity 1: 1.93%
Impurity 2: 1.45%
Total Impurity Content: 3.38%
Regulatory Guidelines
Consult relevant guidelines (e.g., ICH Q3B, USP ) for specific requirements on impurity limits and calculations.
Regards,
Gabriel Chibuikem Eze.
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