GC capillary columns are not packed into the cavity rather they have a stationary phase coating their inner surface. The individual chemical compounds contain capillary GC columns that are used to analyze samples. To test for impurities in the petroleum and pharmaceutical industries capillary column is used and in chemical laboratories, it helps to determine the chemical makeup of a sample. In comparison with a packed column, a capillary GC column has a more efficient separation but by introducing too much of the sample it is more easily overloaded. The capillary GC column is different in size and stationary phase too.
What are the factors to choose GC capillary column
- Stationary phase
While selecting a column, choosing a stationary phase is the most important step as it dictates selectivity or the ability of the column to separate sample components. On the inner wall of a capillary column, a stationary phase is a film chemically bonded. The strength of the analyte phase interactions differs for two compounds and one is retained longer than the other. The physical properties are altered by changing the chemical features of the stationary phase. If two compounds are not get separated on a particular stationary phase then they get separated on another phase of different chemistry. For each chemical class of analytes, each phase provides a specific combination of interactions.
- Established Applications
Gas Chromatography is a mature analytical technique established in the 1950s with many established applications. A written methodology or journal stat in which stationary phase has successfully been used for a given application. The industry arranges the chart to simplify the process of selecting the proper phase. Find the chart that matches your industry and interest and then locates the application within the chart.
- New Application
To guide new applications there is no existing reference. One must have a knowledge of the chemistry of the compounds to be analyzed. Phase selection is generally based on the general chemical principle. Polar columns are usually recommended for the separation of polar compounds and non-polar column is recommended starting point for the analyses of non-polar compounds.
What is a Gas chromatograph?
An analytical technique that is used to separate and detect the chemical components is known as Gas Chromatography. These chemical components are organic molecules and gases and components need to be volatile.
Principle of Gas Chromatography
In a gas stream, the sample solution injected into the instrument enters which transports the sample into a separation tube known as the column. Inside the column, various components get separated and the detector measures the quality of the components that exit the column. A standard sample with a known concentration is injected into the instrument, to measure a sample with an unknown concentration. To calculate the concentration the standard sample peak appearance time and area are compared to the test sample. The capillary columns produce sharp peak shapes, achieve excellent separation performance, and are suited to high-sensitivity analysis.
Compounds that are difficult to analyze with Gas chromatograph:
- The compounds such as inorganic metals, ions, and salts do not vaporize
- Compounds that are chemically unstable and highly reactive
- Compounds contain a carboxyl group, a hydroxyl group, an amino group
- Compounds for which standard samples are difficult to explain
Conclusion
Across most industries, GC is a widely used technique and is used for routine analysis through research. It includes mass spectrometry as it is a robust technique and is easily hyphenated to other techniques. GC is limited to analyzing volatile compounds and more polar analytes can stuck or lost in the GC.
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