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Specificity

hi…

can any one advise that

is it necesary to show selectivity of all known impurities in Assay method?

where although it is proven in related substances method.

where the difference in

  1. chromatographic conditions
  2. concentration of sample

1) chromatographic conditions

Upendra, Yes ,you must prove that no known impurity elutes at the RT of your analyte peak .This is to be proved as how your new chromotographic conditions will satisfy this criteria.

  1. concentration of sample[/quote]

      If you change only the concentration of your analyte,(Assuming that the all other conditions remains unchanged) It may not  be required to prove impurity interference as it has already been proved in RS analysis.

If you change your sample concentration then you have to repeat your analytical method parameters , especially linearity, accuracy , if you are decreasing your concentration at v low level then u must repeat specifity criteria as well.

  1. specificity criteria typically for Assay Validation .(Content or potency) is to demonstrate that analyte is not interfered from impurities, degradants, matrix, etc its not necessory to go for known impureties selectively. Specificity is to check no interferences frm impurities, degradants, matrix, etc. it is to be revalidated in case of change in composition of master formula either quantitative or qualitative.
  2. If the change in sample concentration is out of the previously validated range then its desirable to revalidate Linearity and accuracy. Specificity is to check no interferences frm impurities, degradants, matrix, etc.be revalidated in case of change in composition of master formula either quantitative or qualitative.

Regards,
Shahid Ali
QA Manager
Addis Pharmaceutical Factory SC, Ethiopia

Yes Specificity should be checked for assay to prove there’s no interconversion occurs between the impurity and the main peak.In Related substances method validation we are checking only the interference in retention time but not the interconversion.Some cases where this interconversion will happen.Moreover you have told that the chromatographic condition changes so definitely you have to do.

[quote=upendrapendse]hi…

can any one advise that

is it necesary to show selectivity of all known impurities in Assay method?

where although it is proven in related substances method.

where the difference in

  1. chromatographic conditions
  2. concentration of sample[/quote]

It necesary to show selectivity of all known impurities in Assay method because for assay method sample conc differ