Location:

Peak Table tab page
Report Variable (Peak Table)

Type:

String

Dimension:

---

Value Range:

External; Internal; Internal/External; Use this peak as internal Standard

Default:

External

Can be combined with:

Use sample amount as reference (only with Use this peak as internal Standard)

Related Parameter:

Amount

Description:

The Standard parameter indicates the standard method to be used for calibration. For a detailed description including numerical examples, refer to  Calibrating.

Function:

External

The calibration curve determines the area/amount ratio. During calibration, the calibration coefficients are calculated from mixtures of known components (see Calibration Function and Theory of Calibration  Standard Methods).

Internal

Calibration corresponds to the External Standard method. In addition, an Internal Standard is added. The internal standard itself is calibrated as all other peaks. When performing the integration, the calculated amounts of the remaining peaks are corrected by the nominal/actual ratio of the internal standard.

Chromeleon recognizes any number of internal standards. Theoretically, each peak may have its own internal standard! Furthermore, the standard method may be selected for each peak individually.

During calibration, the amount ratio (instead of amount against area) is displayed in the diagram with regard to the respective peak. From these data points, the calibration function is calculated.

During integration also, the area ratio is inserted into the stored calibration function and the amount ratio is calculated.

 Tip:

Before you can use this option, at least one internal standard must be defined (see Use this peak as internal Standard). Select an ISTD peak in the Associated ISTD Peak check box.

Entering Several Internal Standards

It is also possible to define several internal standards. Via the F8 box, define the respective peaks of the peak table in the Standard column of the peak table as ISTD peaks. The corresponding line of peak table has a yellow background.For the remaining peaks, enter the standard method to be used (external, internal/external, internal). If this should be performed in relation to an ISTD peak, it is possible to choose between the previously defined ISTD peaks.

Internal/External

When calibrating with an internal standard, calculation is with area and amount ratios instead of absolute areas and amounts. During integration, the area ratio is inserted into the saved calibration function to calculate the amount ratio. The result is the amount in relation to its reference peak. Each peak can have its own internal standard.

Calibration does not vary from the external standard method, except for a defined peak (that is, internal standard) being added to the analyses. The internal standard is calibrated as all other peaks. During integration, the calculated amounts of the other peaks are corrected according to the relation of the internal standard to the actual peak.

 Tip:

Before you can use this option, at least one internal standard must be defined as well (see Use this peak as internal Standard). Select an ISTD peak in the Associated ISTD Peak check box.

Use this peak as
Internal Standard

Select this option to define the current peak as ISTD peak. Select the Use sample amount as reference check box to use the amount of the internal standard from the ISTD amount column of the sample list instead of the Amount columns of the QNT peak table. In this way, you can enter a different amount of internal standard for each sample.

 Tips:

For internal standard as well as internal/external standard methods, a substance whose concentration is known, must be added to the standards and to the analyses. This can be conveniently carried out by means of an appropriate Autosampler. Quantitative accuracy reached with this method, exceeds that of the external standard method by one unit.

For these two options, the name of the internal standard must be indicated.

Internal standard methods compensate even small injections deviations, since possible loss or excess apply to the internal standard as well.