From the oil analysis lab, Gas chromatography is becoming more and more crucial for properly determining the concentrations of contaminants especially fuel and glycol in used oil samples. In transformer oil analysis, the process is used to determine the concentrations of dissolved gases within the oil sample, which can be used with gas analysis and other processes to evaluate electrical faults within a transformer or oil insulated electric components. Gas chromatography is one of the most frequently used approaches in modern analytical chemistry. In its basic form, gas chromatography is used to separate complex mixtures of different molecules based on their physical attributes, such as polarity and boiling point.
It is the ideal tool to analyse gas and liquid samples comprising many hundreds or even thousands of different molecules, allowing the analyst to identify both the types of molecular species present and their concentrations. Gas chromatography can be divided into Two classes, gas-liquid chromatography and gas-solid chromatography. In both cases, the technique requires the separation of components of a gaseous sample, using a static stage, either a normal liquid in case of gas-liquid chromatography, or a normal solid in case of gas-solid chromatography. Considering that the overwhelming majority of evaluation criteria used for hydrocarbon Analysis rely on gas chromatography, this guide will concentrate exclusively on this system, although the same basic principles apply to both approaches.
In gas-liquid chromatography, it is the interaction between the Gaseous sample the mobile phase and a standard liquid the stationary phase, which contributes to the separation of different molecular components. The stationary phase is either a polar or nonpolar liquid, which, In the case of capillary column, coats the inside of the column, or is Impregnated onto an inert solid that is then packed into the gas chromatography column. A schematic design of a gas chromatography instrument is shown. The fundamental elements are an inert carrier gas, most commonly helium, hydrogen or nitrogen, a gas chromatography column packed or coated with A proper stationary phase, an oven that allows for precise temperature Control of the column and some type of detector capable of detecting the sample Since it leaves or elutes from the column. Gas-liquid chromatography works Since the atoms in the Samples are transported across the column in the carrier gas, but partition between the gas phase and the liquid phase.