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Title: Three Columns Gas Chromatograph Analysis Using Correlation Between Components Molecular Weight And Its Response Factor
Author: Anwar Sutan Charles Johnson Jason Laidlaw
Source: 2009 North Sea Flow Measurement Workshop
Year Published: 2009
Abstract: Gas Chromatographs (GCs) are delivered from factory with a multilevel calibration already programmed. While this is an effective method to handle the linearity of the detector, it requires many sets of gases at varying concentrations to obtain the multi level calibration parameters. On site when component parts of the GC are changed such as columns, diaphragm, detectors, etc. The GC may require a new set of multilevel calibration parameters. For a number of reasons this is not always practical to do on site or in the field. Other calibration issues on site can result in the systematic drift of the response factor. This sometimes cannot be detected by the GC automatically as the response factor shift can remain within the tolerance limit from the previous response factor set in the GC controller. Even with the wrong calibration result, the Gas Chromatograph still can give repeatable results, however the results will not be accurate and can increase the uncertainty of the measurement. The repeatability and reproducibility tests are good to prove that a GC is working within limits which are specified in ASTM D1945:1996 3 or GPA 2261:1995 5. However, due to the wide tolerance on some compounds these tests do not guarantee that the GC is working as intended. Using these tests does not ensure that each of the components goes through its intended column and further it does not confirm that all the valve timings are correct. A further analysis is required to check this functionality and this can be done by analyzing the response factor of each components. This paper describes a practical method that can be used to overcome these issues by looking at the correlation between components molecular weight and its response factor, and by looking at the historical response factor data for each component.

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