Hello everybody

Here's the question: if I want to use an internal standard do I have to make a calibration curve for it also? I use Varian Star chromatography workstation v.5.5 Maybe someone uses it also and may help me with this problem.

Regards
Marcin Baranowski

When we were using an internal standard we had to include the internal standard in each of our calibration standards so that at each level our software would be able to calculate the ratio between internal standard and target compounds.

Marcin,

Usually not doing the internal standard calibration would not cause a problem. In a few cases the response for the analyte and the standard could differ very much. For example, using a specific wavelength, the analyte could have a high specific absorbance and the standard a low specific absorbance, resulting a high deviation for the assay. Usually developers select internal standards with simular responses to the detector to avoid a problem. To find out if they have a problem, the calibrate the internal standard. The process only occurs in the development, not the day to day work of the assay.
Jim

Marcin,
The other way your question might be interpreted is that you are asking if you should vary the concentration of the int. std. Since it is added at the same level to all the standards and the samples we typically do not run the int. std. through a linearity curve like the standards. Like above though, it is used in the standards during their linearity determinations.

Regards,
Mark