internal standard

[organicchem]

Hi Everyone
can any one please tell me waht concentration of internal standard to be added for a five point calibration in GCMS analysis. My calibration points are 400 600 800 1000 4000 6000ppb SVOC standard.
My stock internal standard concentration is 20 ug/ml.


Regards

[Don_Hilton]

I tend to pick a concentration toward the center of the curve provided that 1) the peak is large enoug to inteagrate well and 2) does not overload the column. If most of the samples you run will be close to some particular value, you may want to make the internal standard close to that value.