Lab Report Gas Chromatography

Introduction Chromatography is a laboratory technique for the separation of a mixture. The mixture is dissolved in a fluid called the mobile phase, which carries it through a structure holding another material called the stationary phase. The various constituents of the mixture travel at different speeds, causing them to be separated. In fact, the separation is based on differential partitioning between the mobile and stationary phases [1]. Chromatography may be preparative or analytical. The purpose of preparative chromatography is to separate the components of a mixture for later use, and it is a form of purification. For analytical chromatography, it is normally done with smaller amounts of material with the purpose of establishing the

It consists of sample injection port, carrier gas cylinder with pressure regulator, column oven, column (open tubular column and packed column), detector and data system.

1. Sample injection port A sample injection port is used to introduce the sample at the head of column. For optimum column efficiency, the sample should not be too large, and should be introduced into the column in vapour form. The slow injection of large samples may results in loss of resolution and band broadening.

The most commonly used method for sample injection is by using a calibrated microsyringe to deliver a sample volume in the range of a few microliters through a rubber septum and then into the vaporization chamber. The temperature of the sample port is usually maintained at about 50°C higher than the boiling point of the least volatile component of the sample.

2. Gas cylinder with pressure

Columns vary in length and internal diameter which depends on the application type. There are two general types of column, which are packed column and capillary column (open tubular). Packed columns contain a finely divided, inert, solid support material coated with liquid stationary phase. Most packed columns are 1.5 - 10m in length with an internal diameter of 2-4mm. There are three types of capillary column that commonly used in gas chromatography. These include wall-coated open tubular (WCOT) column, support-coated open tubular (SCOT) column and fused silica open tubular (FSOT) column. In WCOT column, the internal wall of capillary is coated with a very fine film of liquid stationary phase. In SCOT column, capillary tube wall is lined with a thin layer of solid support on to which liquid phase is adsorbed. The separation efficiency of SCOT columns is higher than WCOT columns due to the greater surface area of the stationary phase coating. In FSOT column, the walls of capillary fused silica tubes are strengthened by a polyimide coating. This type of capillary column is flexible and can be wound into coils. All of these three types of capillary column are more efficient than packed