Calibration Examples
Compensating Measurement Errors (Internal Calibration)

It is possible to compensate measuring errors, such as deviations that occur during the injection, by calibrating with an internal standard substance, i.e., the Internal Standard. In the purely internal standard method, calibration is performed relatively to the internal standard substance, using area ratios instead of absolute areas.

Sample List

In the simplest case, only one standard sample is available. In this case, the sample list looks, for example, as follows:

QNT Method/Amount Table Tab

Enter the amounts of the single substances contained in the standard sample in the Amount column of the Amount table of the QNT Editor:

QNT Method/Peak Table Tab

The internal standard substance is defined in the peak table. If all three samples contain two relevant substances only as in the example, make the following entries in the Standard column, using the F8 input box.

• For substance 1, select Use this peak as Internal Standard and thus define this substance as the internal standard. (The light yellow background of the line and the ISTD: Internal entry indicate that the assignment is correct.)

• In the F8 input box of substance 2, select Internal. From the Associated ISTD Peak field, select the standard substance serving as internal standard (here: Subst. 1).

• If necessary, repeat this operation for every additional substance that should be calibrated based on the internal method.

After completing the input, the substance 2 is labeled Internal Subst. 1 in the Standard column. In addition, substance 1 is labeled as the internal standard for internal calibration:

Amount Calculation

Chromeleon automatically calculates the amount values for the "unknown" substance. The calculation is performed according to the formula for amount calculation (rel. to ISTD) (for more information, refer to Formula for Amount Calculation (Rel. to ISTD) in the Glossary section). Chromeleon calculates the amount for substance 2 adapted by the deviation of substance 1.

For an overview of the different calibration possibilities with internal standard substances provided by Chromeleon, refer to Calibration Examples  Calibrating with an Internal Standard Substance.