How To Choose The GC Capillary Column?
Capillary columns are not packed into the cavity as the columns are gas chromatography columns with a stationary phase coating their inner surfaces. Samples are examined using capillary GC columns to identify the specific chemical substances they contain. The capillary column is used in clinical laboratories to assist identify the chemical composition of a sample and in the petroleum and pharmaceutical sectors to test for contaminants. As compared to a packed column a capillary GC column has a more efficient separation of the sample than a packed column. The main difference is in the stationary phase and the other difference is in the types and sizes of capillary GC columns.
How to choose GC capillary column?
With the column, an optimized chromatographic separation begins. There are four factors on which the selection of a GC capillary column for any application is based:
Stationary Phase
Column I.D.
Film thickness
Column length
· Stationary Phase
While selecting a column it is important to choose a stationary phase as it dictates the selectivity and ability of the column. A stationary phase should be selected based on the application to be performed and is the film chemically bonded to or coated on the inner wall of the capillary column. The separation procedure is based on the variations in the chemical and physical characteristics of the injected organic molecules and their interactions with the stationary phase. One molecule is kept longer than the other when the analyte-phase interactions between the two compounds are significantly different. Retention time, a measurement of these analyte-phase interactions is the amount of time they are held in the column.
The physical properties of the stationary phase may get affected by changing the chemical features. If the difference in the analyte phase interactions is significant then two compounds might separate on another phase of different chemistry that does not separate on a particular stationary phase. For each chemical class of analytes, each phase provides a specific combination of interactions.
· Column I.D.
Efficiency and sample capacity are the two factors that the current range of commercially available column internal diameters enables. It requires a sacrifice from the other by optimizing one of these factors. For a given application the ideal I.D. is dependent on the analytical needs. Depending on the demands of their application, users can optimize either efficiency or sample capacity using columns with a smaller or bigger I.D. The capillary column efficiency is measured in plates or plates per meter and increases as the I.D. of the column decrease.
· Film Thickness
The optimal film thickness may be different depending on the application. Most 0.25 mm I.D. columns have a 0.25 or 0.50 um film thickness. The decrease in film thickness is sharper peaks and reduced column bleed. These benefits increase the signal to noise. Increasing film thickness leads to increased analyte retention and increased elution temperature.
· Column length
A 30-meter column provides the best balance of resolution, analysis time, and required column head pressure.
What is a hydrogen generator and how it works?
Hydrogen Generators for GC are a cost-effective solution to the use of high-pressure H2 cylinders. It is a safe and convenient alternative that offers consistent purity for reliable results. When changing the cylinders will eliminate the risk of contamination. Using distilled or deionized water hydrogen is produced through a polymeric ion exchange membrane. Hydrogen that is ready for analysis and oxygen that is discharged into the surrounding air are the two major components of water that are separated through electrolytic dissociation.
Different technologies are used to dry the hydrogen produced, including desiccant cartridge drying, Permapure drying, and adsorption drying with automated regeneration on two cartridges. The purity of the gas produced will vary depending on the hydrogen drying technology.