Limitations Of Gas Chromatography

Decent Essays
Introduction
This poster will hopefully give the reader a brief introduction into the history, workings, uses and limitation of Gas Chromatography.

The history section looks at some of the major contributors, from the discovery of chromatograph in 1906, by Tswett, to the production of a commercial Gas Chromatographer in 1955, by Perkin-Elmer.

The workings, will cover both the parts of the instrument and the stages a sample goes through in order for the result to reach the display monitor. Limitations will be shown.

Finally, a case study – The Sarin Gas Attack in Japan in 1994 and 1995 caused 19 deaths and many injuries - will show where Gas Chromatography has been used to assist with solving a crime.

History
1906: Mikhail Tswett separates
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1941: Martin and Synge uses paper chromatography. First to use liquid to liquid mobile/stationary phase known as partition chromatography.
1949: James meets Synge and is introduced to Martin. It was at this time that Martin suggested, “Why don’t we have a go at the gas chromatogram?” (A. T. James, 1995 para 11). This they did, while making the components of the instruments themselves. A schematic of their chromatograph can be seen in figure 1.
1955: The first commercial GC was developed and produced in May, 1955, by the Perkin-Elmer Corporation. It was known as a ‘Vapour Fractometer’. (Figure 2) The company continues to refine their instruments and is still selling Gas Chromatographs, today. (Figure
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In the column – the stationary phase – is the high boiling liquid where the sample is separated into components according to their solubility and boiling point. The column‘s temperature is controlled in an oven.
4. The detector is where the amount of sample is measured
5. The integrator/data analyser is where the data analyses takes place. The signals from the detector are digitalised and used for mathematical calculations to determine peak areas, heights, widths and retention times. (McNair, 2009)
6. The graph shows retention time and amount of analyte in the sample, in relation to the other analytes. In Fig. 5 we see that the first analyte out of the column was methanol, in 1.2 minutes – this time is known as retention time and is the amount of time it took for the analyte to leave the column - but it does not have the highest peak. The highest peak being isopropanol, with a retention time was 1.9 minutes. It simply tells us that methanol requires less heat to be vaporised and that the highest concentration of an analyte in the sample is isopropanol.

Limitations
Samples need to be heated at high temperatures, so only samples that are volatile and that can be easily vaporised can be tested. “Thermally labile compounds can break down inside the inlet before even reaching the column, reducing sensitivity and resulting in inaccurate results. “ (Kelly & Parnell,

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