What is it?
Gas chromatography is a variation of chromatography used in analytical chemistry for separating and analysing components that can be vaporised without decomposition ("Gas Chromatography", 2016). This technique involves using a gas as the mobile phase. There are two types of gas chromatography:
• Gas-solid chromatography – separates substances on the basis of their different strengths of adsorption on the solid
• Gas-liquid chromatography – separates substances in the basis of different solubilities in the stationary phase
How does it work?
In a gas chromatograph the sample being analysed is inserted with a syringe into a heated flowing gas, usually helium or argon. The sample is immediately vaporised and …show more content…
Gas chromatography is very sensitive and is often used to routinely detect microgram quantities of substances and, in many cases, quantities in the nanogram range. Therefore it is often used in forensic chemistry to identify pesticide residues in foods, illegal drugs and steroids in athletes, trace pollutants in air and water and a wide variety of substances found at a crime scene. This technique is relatively quick and easy to perform, but the instruments required are relatively expensive.
• Has a high resolution power compared to other methods thereby allowing it to detect small quantities of substances
• Provides relative good and accurate data
• Easy and quick to perform
("Disadvantages & Advantages of an GC | Frndzzz.com", 2016)
• Only volatile substances can be used in this method
• Caution is required when injecting the gaseous sample
• The sample of gas being injected must be thermally stable so that it is not degraded when heated
• Instruments required are relatively expensive
• Pure samples of all the likely compounds must be available for …show more content…
A forensic analysis will allow the detection of trace amounts of illegal drugs. Given that the analysis would require the detection of extremely small molecular weights, the use of Gas Chromatography coupled with Mass Spectroscopy will yield the best results.
Gas Chromatography involves a sample being vaporised and injected onto the head of the chromatographic column. This method is used to isolate the drug from any mixing agents or other substances that might be combined with it. This procedure involves a small amount being vaporised and injected in the gas chromatograph. Different components of the sample travel through the column at different speeds based on their density. The sample is then funnelled into a Mass Spectrometer where an electron beam hits it, causing it to break apart. How the sample breaks apart determines what type of substance the sample is.
Case Study 4
This scenario involves the analysis of a food sample suspected of containing illegal additive. A forensic analysis will be able to identify the components of the food sample and detect if any illegal additives are present. Given that Atomic Absorption can achieve the required low detection limits, and offers maximum ease of use, sensitivity and accuracy it is ideal for this