Chromatographic Control

The computer that handles the output from the detector also provides other information in the analytical report. Today, most chromatographic systems, gas and liquid, have a dedicated computer which, as well as processing the information provided by the detector, will also control and record the operating conditions of the chromatograph.

Temperatures and flow rates programs, etc., will be entered via the key–board of the computer and the information stored for reporting purposes when required. An example of the print-out from a Perkin Elmer, LC140 liquid chromatograph giving the operating conditions and analytical results is shown in figure 42.

There are two procedures used in GC and LC for quantitative analysis: the first employs a reference standard to which the peak areas or peak heights of the other solutes in the sample are compared; the second is a normalization procedure where the area (height) of any one peak is expressed as a percentage of the total area (heights) of all the peaks.

The most common method is that employing reference standards. However, if the detector has the same response to all the solutes in the mixture, the normalization method can be used

Quantitative Analysis Using Reference Standards

Reference standards can be used in two ways: the internal standard method where a weighed amount of the standard can be added directly to the sample and the area or heights of the peaks compared with that of the standard.