Linearilty

[kvalliappan]

How do you fix the concentration range, based on label claim of a tablet, for linearity studies in HPLC analysis ? Some literature say approximately from 20 to 200% of the nominal range of the analyte. What is meant by nominal concentration?

Thanks for your time

[shaun78]

Nominal concentration refers to product strength.

Say nominal API in a tablet is 500 mg. Suppose the test method dissolves that tablet into 500 mL of solution to make things easy. Nominal test sample concentration is 1 mg/mL.

Sources say validate from 20 - 200%, but typically about 50% to 150% is done, unless you are validating a dissolution assay ... in which case the 20% to 200% applies.

Anyway, getting back to the point, nominal test sample concentration is 1 mg/mL ... if you wanted to validate 50% to 150% as the range of the assay, you would make various solutions that have a concentration ranging from 0.5 mg/mL to 1.5 mg/mL of the active.

It is generally suggested that linearity be validated using a minimum of five points across the assay range.

Hope this helps ...

Shaun