Electron capture detector РІР‚вЂњ It has a cavity that has two electrodes and a radiation source that emits radiation.

One has the carrier gas while the other has the carrier gas and the compound. It detects the molecules of the sample based on two gas streams comparison.

Thermal conductivity detector РІР‚вЂњ It is less sensitive than a flame ionization detector but is perfect for preparative applications because it keeps the sample intact.

Flame Ionization Detector РІР‚вЂњ It is highly sensitive to organic molecules but insensitive to small molecules.

The gas chromatograph separates the compounds and the mass spectrometer identifies the compound according to fragmentation pattern.

Mass spectrometer РІР‚вЂњ The majority of gas chromatography instruments have a mass spectrometer.

What detectors are used in a gas chromatograph?

Image 8 : A gas chromatograph with electron capture detector. The signal is dependent on the rate for which the molecules of solute enter the detector. Mass flowР’В dependantР’В detectors РІР‚вЂњ They destroy the sample.They do not destroy the sample dilution of makeup gas and will lower the response of detectors. Dependant detectors РІР‚вЂњ They are related to solute concentration in the detector.Specific detectors РІР‚вЂњ They respond to just a single chemical compound.Selective detectors РІР‚вЂњ They respond to a wide array of compounds with common physical/chemical properties.

Non-selective detectors РІР‚вЂњ They respond to all compounds with the exception of the carrier gas.Keep in mind that different detectors yield different types of selectivity. Detectors РІР‚вЂњ Various detectors are used in gas chromatography.If a particular sample has a wide boiling range, it would be of help if temperature programming is used. A temperature that is way above the average boiling point of a particular sample could lead to an elution time of 2 minutes to 30 minutes. The maximum column temperature depends on the boiling point of a particular sample. Column temperature РІР‚вЂњ It is controlled within tenths of a degree.The two types of capillary columns are more efficient than the packed columns, but the support-coated open tubular is less efficient than the wall-coated open tubular. It could be a wall-coated (has a papillary tube with walls coated with liquid stationary phase) or open tubular or support-coated open tubular (the capillaryРІР‚в„ўs inner wall has a thin layer of support material like diatomaceous earth wherein the stationary phase is absorbed). Capillary columns РІР‚вЂњ It has an internal diameter that is about a few tenths of a millimeter. Packed columns РІР‚вЂњ It has a divided, inert, and solid support material coated with the liquid stationary phase.Р”В«. Columns РІР‚вЂњ The columns are available in two types РІР‚вЂњ packed and capillary/open tubular.Р”Р„.A micro-syringe is used to inject a sample through the rubber septum and into a flash vaporizer port which is located at the head of the column. What happens when slowly injecting a large sample is it leads to a band broadening and loss of resolution. Sample injection port РІР‚вЂњ it is a must to make sure that the sample is not too large and introduced onto the column as a plug of vapor.It can also be used to check for blood alcohol, food purity, drug purity, and quality of essential oil.It is used to detect processes to check for contamination and to make sure that the process is going according to plan.It is used to find out vapor pressure, activity coefficients, and heart of the solution.It helps separate and purify components in a given mixture.It aids in identifying the composition of a liquid mixture and find out the relative concentration.There are different types of gas chromatography, but the most commonly used method in separating organic compounds in gas-liquid chromatography. Liquid-solid column chromatography is used to separate the organic compounds in a given solution. He used it as a separation method of separating compounds. Gas chromatography was discovered in the early 1900s by Mikhail Semenovich Tsvett. (2, 3, 4, and 5) The discovery of gas chromatography If a sample with an unknown concentration is measured, a standard sample with known concentration is being injected into the gas chromatograph. The number of components that exit the column is measured by the detector. The components of the sample are separated inside the column. A carrier gas is used in the form of helium or nitrogen. The sample solution is placed into the gas chromatograph and enters the gas stream which transports the sample into the column (separation tube).

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