Gas Chromatography

This Slides has been re-taken from several chromatography researches by Mahmoud Galal zidan special Chemistry , Faculty of

science , Tanta University , Egypt E-Mail : M7moud.zidan@yahoo.comE-Mail : m7moud.zidan@aol.com E-Mail : M7moud.zidan@Gmail.comFacebook : www.fb.com/m7moud.zidan Twitter : www.twitter.com/m7moudzidaneTel : +201272122218 /+201273937378

How the device Work ?

Index Definition of GCAdvantage of GCAgriculture Uses Pharmaceutical Uses Medical Uses Petrology Food Packing Drivers’ safety

Definition of GC Gas Chromatography is an

instrumental technique used in analytical chemistry for separating and analyzing compounds that can be vaporized without decomposition .

Advantage High speed: analysis in a matter of

minutes and routine and less few analysis In a matter of few seconds also possible .

High sensitivity we see both rapid analysis as well as high sensitivity .For ex is a 21/2 min of separation three common pesticides ,Methyl parathion , malathion ,Ethion at Pg levels( Pg means 10-12grams ) these are parts per billion. This is very good example of both the high speed as well as a very sensitive detection .

Agriculture Uses Determination of Pesticides Residue in Aquaculture

Products Detection and Quantitation by Gas Chromatography Agricultural chemicals such as fertilizers and pesticides have made an important contribution to agriculture.

Pesticides protect crops from pests and diseases , They have brought about large yield increases , since almost all chemicals that can kill pests are also potentially damaging to human health. Legislation requires that pesticide use is appropriately controlled and maximum residue levels (MRLs) not be exceeded , Detection method is the process of identifying the pesticides and determining their concentrations. With the aid of an analytical instrument , such as a gas chromatograph (GC) , we can obtain information about the original sample by running a standard solution containing the pesticide(s) at a known concentration and comparing it with the sample.

Pharmaceutical Uses The pharmaceutical industry also heavily uses GC and HPLC to determine

the purity of reagents, the identity of synthesis products , and the identity of medicines and illicit drugs . A few examples are shown below :

In most forensic applications of GC, a sample is prepared by dissolving it in a solvent, and the solution is injected into the instrument using a syringe. For example, to analyze a white powder suspected of being cocaine, a small portion is weighed out and dissolved in a solvent such as methylene chloride, methanol, or chloroform. A tiny portion of the sample is then drawn up into a syringe and injected into the heated injector port of the instrument. The mobile phase gas (called the carrier gas) also enters the injector port, picking up the volatilized sample and introducing it into the column where the separation process occurs. If the sample contains cocaine, it will emerge from the column at a given time (known as the retention time) that can be compared to the retention time of a known standard sample of cocaine. The retention time in conjunction with information obtained from the detector is used to positively identify the compound as cocaine if indeed it is present. Another method of sample introduction for GC is called pyrolysis, in which a solid sample such as a fiber or paint chip is heated in a special sample holder to extreme temperatures, causing the sample to decompose into gaseous components that can then be introduced into the GC. Pyrolysis is used when the sample is not readily soluble in common GC solvents.

Medical Uses GC-MS used in thyroid cancer study Gas

chromatography-mass spectrometry (GC-MS) has been used to investigate the pathogenic differences in a form of cancer according to gender and menopausal condition .In a study published by BMC(biomed central services publish original research on oncology)) Cancer, scientists sought to evaluate the metabolic changes in urinary steroids in men and pre- and post-menopausal women with papillary thyroid carcinoma (PTC).GC-MS was used to measure the urinary concentrations of 84 steroids in all of the patients against corresponding controls .The metabolic ratio of 2-hydroxy estrone to 2-hydroxy-17 beta-estradiolin particular showed gender differences in PTC patients .It is hoped the findings could help better understand the pathogenic differences in PTC according to gender and menopausal conditions.

Petrology GC can also be used to determine the

identity of natural products containing complex mixtures of similar compounds. For example , the geographic source of crude oil or natural gas can be determined by the “finger print”, or relative distribution of major and trace compounds in each oil Natural produce oils, such as food products or fragrances, can be identified by GC-FID or GC-MS. A few examples of the separation of these complex mixtures are shown below.

Drivers’ safety Breath Alcohol Testing Drunk driving costs countless lives

and destroys families around the world each year. In most countries drunk driving is illegal and in pursuing these laws the police utilizes breathalyzer tests . Test equipment must be perfectly calibrated to stand up in a court of law. Therefore one of the calibration methods is to use a calibration gas. The demands on such a calibration gas are strict, it must be easy to use, be stable, portable and fool-proof. Linde produces and delivers such calibration gases with the Breath cal program Determination of free cholesterol in milk fat : rapid and direct gas chromatographic (GC) method for determining free cholesterol in milk fat using a capillary column and programmed-temperature vaporizer injector was assayed Soil and Water Measurement Contamination of soil and water can come from many areas, including acid rain, pesticides industrial waste, landfill, and raw sewage. Analytical procedures include GC/MS.

Food Packing Food packaging Modified Atmosphere Packaging of food,

or MAP, is a natural shelf-life-enhancing method that is growing rapidly on an international scale. It often complements other techniques, such as high-pressure and microwave methods or oxygen absorption. The correct gas mixture in MAP maintains high quality by retaining the original taste, texture and appearance of the foodstuff.

The gas atmosphere must be chosen with due consideration of the particular foodstuff and its properties. For low-fat products with a high moisture content, it is especially the growth of micro-organisms that has to be inhibited by using Carbon dioxide. On the other hand , should the product have a high fat content and low water activity, oxidation protection is most important and inert Nitrogen would be the preferred choice.

References Sample Preparation Techniques for Gas

Chromatography Nicholas H. Snow and Gregory C. Slack Physicochemical Measurements by Gas

Chromatography Mary A. Kaiser and Cecil R. Dybowski Petroleum and Petrochemical Analysis by Gas

Chromatography Edward F. Smith, Mark E. Craig, and Clifford C. Walters Clinical and Pharmaceutical Applications of Gas

ChromatographyJuan G. Alvarez Environmental Applications of Gas

Chromatography John L. Snyder By: Mahmoud Gala

Zidan