Technical data

120 Understanding Your Agilent ChemStation

5 Quantification

ESTD Calculation

The ESTD procedure is the basic quantification procedure in which both

calibration and unknown samples are analyzed under the same conditions.

The results from the unknown sample are then compared with those of the

calibration sample to calculate the amount in the unknown.

The ESTD procedure uses absolute response factors unlike the ISTD

procedure. The response factors are obtained from a calibration and then

stored. In following sample runs, component amounts are calculated by

applying these response factors to the measured sample amounts. Make sure

that the sample injection size is reproducible from run to run, since there is no

standard in the sample to correct for variations in injection size or sample

preparation.

When preparing an ESTD report, the calculation of the amount of a particular

compound in an unknown sample occurs in two steps:

1 An equation for the curve through the calibration points for this compound

is calculated using the type of fit specified in the Calibration Settings or

Calibration Curve dialog box.

2 The amount of the compound in the unknown is calculated using the

equation described below. This amount may appear in the report or it may

be used in additional calculations called for by Multiplier, Dilution Factor,

or Sample Amount values before being reported.

If the ESTD report is selected, the equation used to compute the absolute

amount of component x is:

where:

Responsex is the response of peak x;

RFx is the response factor for component x, calculated as:

M is the multiplier.