How to choose Gas Chromatography Column?

How to choose Gas Chromatography Column?

Before you start separating the complex compounds of your mixture through chromatography, the most important decision is to choose the right column.

Without the right column, you are not going to get the correct results. There are some criteria on which the selection of the right Gas Chromatography Column depends. I will be trying to discuss briefly each of the four criteria.

So let’s start with what are the four criteria on which the selection of a proper chromatography column depends.

1. Stationary Phase 2. Column Length 3. Column I.D. 4. Film Thickness Stationary Phase This is the most important in deciding the type of column you need for your gas chromatography process. It decides the ability and selectivity of the column to separate the components of the mixture into individual components.

So what is a stationary phase? A stationary phase is a layer or film which is coated or chemically bonded on the inner wall of any capillary column. Selecting a stationary phase is important because it decides the interactions between the organic compound injected and the stationary phase.

This means that the stronger the interaction between the analyte and the phase, the longer time the analyte is retained inside the capillary. While the other compounds which do not form strong bonds with the stationary phase go outside sooner. The time of retention of the mobile phase inside the column is the measure of the phase-analyte interaction.

There are wide variations in the capillary column phases. This is because, for each type of chemical property of the stationary phase, the relationship of the analytephase reaction differs. It may not be possible to have the same reading for a particular combination of analyte and stationary phases.

Column Length Usually longer the Flame Photometric Detector for GC length, the more is the efficiency or resolution is improvised many times. But the disadvantage is that it increases the backpressure. It is not that doubling the column length will double the resolution.

You can resolve for short columns if you do not require a great resolution for separating the components of a sample. However, decreasing the column id along with a decrease in length can improvise the resolution of screening along with the short length of the column.

Film Thickness If you go for decreasing the thickness of the film then you will get sharper peaks and reduced column bleeds. But the disadvantage will be that you have to increase the operating temperature, decreased analyte capacity, and more interaction between the analyte and the stationary phase.

On the other hand, the increasing film thickness will help in increasing the analyte capacity and lesser analyte interactions with the stationary phase. But you will also observe increased peak widths which mean reduced resolution and more often column bleeds and decreases in optimum temperature.

Column I.D. gThe ideal I.D. depends on the analyte you choose to separate. Column internal diameters maintain a balance between sample capacity or the amount of sample required for sharp edge and efficiency or the number of theoretical plates used.

SOURCE https://quadrexcorp.mystrikingly.com/blog/how-to-choose-gas-chromatog raphy-column