The factors that affect the resolution of a chromatographic column are the type and properties of the stationary phase (particle size, particle size distribution, etc.), packing conditions, column length, type and flow rate of the mobile phase, and the properties of the substances used to measure the column efficiency. details as follows:
(1) The chromatographic length and the properties of the filler, the longer the chromatographic column, the better the analysis between components, but the longer the chromatographic column, the greater the pressure drop, and the input pressure is limited. If the column is too long, the pressure ratio of inlet and outlet will increase, which will affect the separation of chromatographic peaks;
(2) The particle size of the chromatographic column packing is also the main factor. The finer the particles, the better the resolution due to the increase in the surface area, but the finer particles will increase the column pressure drop, which will also have an adverse effect;
(3) The column temperature also has a great influence on the analysis of the liquid chromatograph, because the solubility of the gas in the liquid or the degree of adsorption on the solid surface decreases with the increase of the temperature. In the gas-liquid chromatographic analysis, when the temperature exceeds a certain temperature, Static liquids usually evaporate from the column, so the boiling point of the sample should be considered when choosing the column temperature. Generally, it is slightly lower than the average value of the boiling point of the sample;
(4) The influence of the type of gas chromatograph carrier gas. The commonly used carrier gases are N2, H2, He, Ar, etc. Among them, the molecular weight of H2 and He gas is small, which is conducive to improving the analysis speed, but the medium with higher concentration is easy to form diffusion in it, which affects the degree of separation, so in the actual measurement Medium H2 and He gases are generally used in areas with low medium concentration and increase their flow rate to reduce the influence of diffusion. The advantages of gases with larger molecular weights such as N2 and Ar are that the diffusion effect is small, and the disadvantage is that the pressure drop in the column is large and the flow rate is slow, that is, the analysis period is long;
(5) Influence of carrier gas flow rate. The residence time of the medium on the stationary phase mainly depends on the characteristics of the medium itself (volatility, polarity, etc.) and the flow rate of the carrier gas. Therefore, the speed of the flow rate directly affects the degree of separation;
(6) The influence of injection time and injection volume. The injection time should be as short as possible. In principle, instantaneous injection will improve the resolution. The injection volume should be as small as possible, but should be identifiable by the detector.
Therefore, the improvement of chromatographic column resolution can be achieved by increasing the column length, reducing the injection volume, reducing the carrier gas flow rate, lowering the chromatographic column temperature, increasing the vaporization chamber temperature, and reducing the dead volume of the system.