Chromatography Forum

Hello sir,
Currently I am working on a injectable product having 1 API label claim 0.2 mg/mL and other API has label claim 9mg/mL. in RS analysis both have same wavelength..and due to low label claim sample injeted as such(as per monograph assay method)....I have prepared Spiked sample in placebo sample during method development....
I have 2 label claim for unknown of both,so both placebo injection is required to confirm unknown for specific analyte.
If I Spike i impurity in sample then my sample concentration will change due to as such sample injection in method.
I want to know that, is there any other method to prepare Spike sample for method precision?
Thanks & Regards
Pratik

Pipet 9.00 ml sample (yes, there are 9.00ml class A volumetric pipets) into a 10ml class A volumetric flask. Add spike of active(s). Mix and dilute to 10.00ml with your solvent.

And I'd do similar with placebo.

Thank you for your reply.
But when diluting 9ml Sample to 10 ml with diluent.my sample concentration will change for API 0.2 mg/mL to 0.18 mg/mL and for other analyte 9mg/mL to 8.1 mg/mL... wheres I am using as such sample for injection....then may I have to change label claim for this type of calculation?..
I have to Spiked 3 impurities for 2 analyte in as such samples.then may I proceed through mix impurity stock solution?

Me? I'd include the dilution and make an automatic correction in the automated calculations. Like a 10/9 factor.