Specification of HPLC Column
Hawach HPLC column is composed of a column tube, pressure cap, clamping sleeve (sealing ring), the screen plate (filter), joint, screw, and so on. The column tube is made of stainless steel. When the pressure is not more than 70 kg/cm2, thick-wall glass or quartz tubes can also be used. The inner wall of the tube requires a high degree of finish.
The difference between C18, C8 and C4 HPLC Column
HPLC columns C18, C8, and C4 have commonly used columns in the application, and each of them provides special properties. C18 has a strong retention ability for nonpolar compounds. C8 and C4 have a shorter carbon chain and are more reserved for nonpolar compounds than C18 weak, so the strongly retained compounds can be replaced by C8 and C4.
In addition, because of the short-chain length, C18 and C8, and C4 in the separation of different points, the sub-size of the material will have a choice of differences. Moreover, the carbon content of C18 is almost twice that of C8, and that of C4 is the lowest. C8, C4, and other short-chain alkyl bonding phases are suitable for small polarity to reduce retention and shorten the time of analysis.
Importance of Performance Assessment
Whether filled or purchased by yourself, the performance of the HPLC column should be examined before use, and it should be re-examined during use or after placing it for a period of time. The column performance index includes column pressure under certain experimental conditions (sample, mobile phase, flow rate, temperature), theoretical tray height and tray number, symmetry factor, capacity factor, selectivity factor repeatability, or separation degree. Generally speaking, the reproducibility of the volume factor and selectivity factor is less than ±5% or ±10%. When comparing the column effect, you should also pay attention to whether the out-of-column effect has changed.
Methods of Performance Assessment
It must be pointed out that the filling technology is an important link in the acquisition of high-performance liquid HPLC columns, but the fundamental problem lies in the performance of the packing itself and the reasonableness of the structure of the matching chromatograph system. A qualified column evaluation report should give the basic parameters of the column, such as column length, inner diameter, packing type, particle size, column efficiency, symmetry, and column pressure drop.
Influence of Different Specifications
Hawach HPLC column specification includes two aspects: column length and column inner diameter. The selection of column specifications directly affects the analysis speed, separation ability, detection ability and solvent consumption per analysis, etc.
Property of Large and Small Inner Diameter
For the same analytical time and degree of separation: Columns with large inner diameters consume more solvent than columns with small inner diameters. Smaller inner diameter columns also require less sample size for the same detection signal. Therefore, when the sample size is limited, the small inner diameter column can be used. Although the column length increase can improve the separation effect, the resistance also increases, and the inlet pressure must be increased.
The long column can give high separation, the short column can provide rapid separation, and you can choose the appropriate chromatographic column according to the sample. With a narrow inner diameter, small particle sizes cause high column pressure, column pressure is the main obstacle that affects both the increase of separation degree and the decrease of analysis time. Separation, analysis of time and column pressure choose two of them, then the third factor will be chosen.
