 Myself, Dr. Nitin Gramopadhyay, today we are going to learn a topic, analytical chemistry and from that topic, one beat that is known as gas liquid chromatography. Now, this is the learning outcome for today's session. At the end of this session, students will be able to learn the terms chromatography and types of chromatography, then we will learn construction, working and applications of chromatography. This is the particular content of the today's session, definition of chromatography, classification of chromatography, instrumentation and applications of chromatography. Now, what do you mean by chromatography? It is one of the analytical tool, it is one of the analytical process that is used to find out, what is the percentage of chemicals, different combinations present in a given sample. Now, what is that chromatography? The term chromatography and its principles were first discovered by Mikhail Tasvet. He passed the plant extract over column of calcium carbonate and washed it with petroleum ether. When the plant pigments were separated into number of horizontal colored bands, since the separated pigments were colored, the method was called chromatography, meaning colorful writing. Chromatography is defined as the separation of a mixture into its pure components by continuous distribution of the components between the stationary and the mobile phase. Now, this is the classification of method chromatography, adsorption chromatography, partition chromatography, exclusion chromatography, ion exchange chromatography and then the partition chromatography divides into the different types, thin layer chromatography, column chromatography, paper chromatography, again the column chromatography divides and here the gas chromatography divides into gas liquid chromatography. So, this is the classification of the different types of the chromatographic methods. Now, what do you mean by gas liquid chromatography? In GLC, the separation of components takes place due to the difference in solutions behavior that is partition coefficient of the components. In GLC, the column packing consists of granulated inert support carrying a non-volatile liquid phase. The supports are of either calcite or fire brick. These supports are in the form of particles and size of the particles is governed by length of the column. Species of liquid for stationary phase, the liquid that is used as a stationary phase should not react with the sample to be analyzed. It should be inert. It should not be volatilized by the flow of the carrier gas. So, the liquid should remain in a liquid form. Due to the flow of the gas or due to some heating, the liquid should not convert into vapors. It should show different solubility for different species present in the sample. The selection of the stationary liquid phase depends upon the type of substances to be separated and their complexities. Some commonly used stationary liquid phases are hydrocarbons, ethers, ketones, etc. Silicon oil for general purpose, polyglycols for separating alcohols, acids, amines, etc. are used. The capillary column is made up of nylon, glass, copper or stainless steel tubing. These are generally 5 to 500 mm in length and 0.1 to 1 mm in diameter. It is coated with the stationary liquid phase on the inner surface by special techniques. Now, this is the flow diagram of the GLC that is block diagram. If you see here, this is the tank for carrier gas which is called as the mobile phase. So, this is the source of the mobile phase gas. This is the pressure regulator. This is the drying tube because sometimes the gas may consist of the moisture. The moisture is removed when the gas comes through the drying tube. This is the flow regulator and here it is mentioned the sample injection port. That means here we have to introduce the sample under investigation, under our study. Then from here it starts the column here is in the form of the tubing and the columns are either made up of steel, glass, etc. Just now we have learned what is its dimension and length. 0.1 mm to 1 mm is the dimension. Sometime instead of tubing the column is fixed in a coiled structure also and the columns are kept inside the thermostat. This dotted line indicates the thermostat. The thermostat is heated and then one port is connected to detector, bridge, amplifier and here some sensors are there by receiving some signals from the sample separation. It forms the graph and by reading the graph one can come to know what is the sample that we have introduced. But this method is used to find out the chemical composition of the sample, we do not know. But by reading the graph we come to know that whether the sample consist of the amine. Again whether the amine is primary, whether the amine is secondary, whether the amine is aliphatic, whether the amine is aromatic, etc. So we do not know what the sample is but when you put the sample, when you put the experiment performing here, the signals are received by these electronic gadgets and then it plots the automatic graph on a computer screen. By reading that graph one can come to know what is our sample. The essential parts of the apparatus used for gas liquid chromatography are one is the tank for a carrier gas that is mobile phase and injection port of the sample, the column and the detector with recorder. These are the important components of the GLC equipment. Now I would like to ask you one question here, a liquid used as stationary phase for separation of a mixture into its pure components in GLC should be a thing for a moment will come with answer and the correct answer is that inert. Now how it works, the working of the GLC, the column is maintained at a requisite temperature with the help of thermostat. Then the sample is injected in a very small quantity by a syringe into the sample chamber and the sample is vaporized as little time as it is possible and then it enters into the column. Thereafter small quantities of the sample can be injected at regular intervals. The vaporized solutes are carried by moving gas into the column. The different components of the mixture migrate at different speeds depending on their partition coefficient values. Through the column with the continuous flow of carrier gas, each component leaves the column separately in small volumes along with the carrier gas which are then detected by the detector system and recorded in the form of chromatogram showing elution peaks and the time since injection. After passing through the detector, the gas system passes through a sample collector for identification. Now what are the applications of GLC? The small sample size is sufficient for analysis is a good thing, we require a very small sample size. The GLC is used in the separation of all classes of organic compound. So near about all organic materials we can analyze, we can separate by using the chromatography technique because chromatography is a lab technique also to learn and a separation technique also to separate. If you have a mixture of organic material, we can separate it. For example, when we prepare the nitroaniline from the nitrobenzene. So what happened? Three derivatives we can get two nitroaniline, four nitroaniline and the six nitroaniline. So all the three isomers we can separate, two nitro separate, four nitro separate and the six nitro. It is a routine analytical tool in laboratories for all types of material. It is used in the petroleum industries for separation of different components from the crude oil. That already we know, the crude oil is a mixture of various component. It starts from the gaseous component to liquid component to semi-solid component to solid component. All the components are present in a crude oil, it is a single oil, it is a mixture. But when that mixture is processed through the chromatography method, the various fractions we are getting, uncondensed gases, methane gas, LPG, etcetera then octandate petroleum products are there, diesels are there, heavy oils are there, lubricating oils are there and finally tar is there. It is used in the petroleum industry for the analysis of crude petroleum products, gasoline, waxes, in cosmetics and perfumes. It is helpful in determining the composition of various cosmetics, quality of ingredients and the components of suitable fragments. It is also used for the product quality control for analysis of commercial products and in forensic chemistry.