Quantification by internal standard
Posted: Wed Mar 07, 2012 6:01 pm
by chandra
Hello to everyone,
I want to quantify 14 compounds in urine sample so is it required to use 14 internal standards for each individual compound or i can use only one internal standard,please help.
Thanks
Chandra
Re: Quantification by internal standard
Posted: Thu Mar 08, 2012 12:13 pm
by lmh
It depends what you want to correct for. If you are correcting for cosuppression and have 14 chemicals eluting at different times, you will need 14 internal standards eluting at the same times, because cosuppression is an interaction of two chemicals that happen to coelute. If you are correcting for general loss of instrument efficiency as it gets dirty, a single internal standard reasonably chemically-similar to the compounds will already help a lot. If you are compensating for loss of compound during extraction, your internal standard(s) must be chemically similar to the measured analytes, so you can be convinced that the loss of internal standard will match that of measured analyte. That means that you may need only 1 internal standard if all your compounds are closely related, or more, if they are diverse.