Three Conditions for Optimizing the Best Separation Effect of Gas Chromatograph Capillary Column

Capillary gas chromatography is the most important separation technique in gas chromatography separation technology. This type of column has no packing in the column, and the hollow column has small resistance and the length can reach 100 meters. The fixing liquid is directly applied to the pipe wall, the total inner wall area of ​​the column is large, and the coating can be thin, and the mass transfer resistance between the gas phase and the liquid phase is lowered. These factors make the column efficiency of the capillary column Great progress has been made.

Generally speaking, a capillary column consists of two parts - the tube body and the stationary phase. The pipe body generally uses fused silica or stainless steel as the basic material: there are many types of stationary phases. Most of the stationary phase is a liquid or gelled high-score, highly thermally stable polymer, most commonly polysiloxane (sometimes misunderstood as siloxane) and polyethylene glycol, plus one The class is a polymer or zeolite composed of small porous particles (for example, alumina, molecular sieves, etc.).

Among the conditions that affect the separation effect in capillary column manipulation, there are three main points. After these three conditions are effectively optimized, the separation effect can be greatly improved.

1. Injection method.

Since there are many injection methods in capillary chromatography analysis, different injection methods should be selected for different analysis purposes in order to effectively improve the efficiency of the column. The residual analysis should be selected for splitless injection or on-column injection, and purity analysis should be more selective for split injection. The split ratio is determined by the content of the analyte. However, the split injection has an influence on the quantitative accuracy, and the larger the split ratio, the worse the quantitative accuracy.

2. Carrier gas flow.

The carrier gas flow rate is set according to the combination of the column length of the capillary column, the column diameter, the film thickness, and the composition of the analyte. High flow rates can improve analytical efficiency, but sometimes the efficiency may be reduced due to insufficient exchange between the analyte and the stationary phase. Therefore, in the actual analysis process, the flow rate should be set appropriately under the condition of separation to improve the analysis efficiency.

3. Column temperature control.

Column temperature is the most important parameter affecting the efficiency of chromatographic separation and analysis. Therefore, according to the purpose of analysis and the nature of the measured object, such as the boiling point of the measured object, the polarity of the measured object, and the number of components to be tested, it is optimized by experiment. The right column temperature. The control of the column temperature is manifested in the initial temperature, the heating rate and the end temperature. Only the temperature control of each stage is good, and the separation effect can be improved.

The emergence of capillary columns is an important milestone in the development of gas chromatography. Negative gas chromatography has greatly improved both in separation efficiency and analysis speed. The emergence of new capillary columns has also led to rapid development of this technology. At the same time, in the actual operation, continuous optimization of conditions can make the separation effect more effective.

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