Internal standard

[kvalliappan]

Hi,

I would like to know whether internal standard must be used when one is developing a HPLC method for the determination of an anlyte in a biological matrix viz. plasma, where lot of sample workup will be there? Will external standardisation method be OK?

Thanks for your time.

[tom jupille]

No way to tell a priori. If the dominant source of error is sample workup, then an internal standard should improve repeatability. If the dominant source of error is S/N (noise, integration problems, etc.), then an internal standard will make things worse.

If you want to be safe, develop the method with the internal standard and then compare results with and without.

[kvalliappan]

Dear Mr. Tom Jupille,

Thanks for the information.