What Should We Know Before Using a FLASH Column?
About chromatographic column
Before choosing a chromatographic column, learn more about your samples and impurities, their type structure, polarity, acidity and basicity, molecular weight, and so on. HAWACH manufactures different chromatographic columns, like the SPE, FLASH, and HPLC column. The FLASH column can be used as a columnar stationary phase for liquid chromatographic separation. It is composed of a column tube, pressure cap/compression sleeve, sieve plate (filter), packing, joints, etc., and can be used for liquid chromatography analysis and preparation. Before using the FLASH column, perform the column performance test and save the results as a reference for evaluating the changes in column performance in the future.
Note, however, that column performance may vary depending on the sample, mobile phase, column temperature, and other conditions; Plus, the column performance test is carried out according to the conditions in the column factory report. The results obtained are comparable. Pay attention to the following matters when using FLASH columns:
1. Sample pretreatment
a. Use the mobile phase to dissolve the sample.
b. A pretreatment column was used to remove highly polar or irreversibly adsorbed impurities by the column packing.
c. Use a 0.45μm filter membrane to filter and remove particulate impurities.
2. Preparation of mobile phase
FLASH column is the purpose of separation by the mass exchange of sample components between the column packing and the mobile phase in a quick way. So, the following characteristics of the mobile phase are required.
a. The mobile sample has a certain solubility relative to the sample to ensure that the sample components do not settle or remain in the column for a long time.
b. The mobile phase is inert and does not react with the sample (except in special circumstances).
c. In order to obtain a good separation effect when using long analytical columns, the viscosity of the mobile phase should be as small as possible. Meanwhile, reduce the column pressure drop and extend the service life of the liquid pump (the method of increasing the temperature can be used to reduce the viscosity of the mobile phase).
d. The mobile phase’s physical and chemical properties shall be compatible with the detector used. It is best to use a solvent with low UV absorption if a UV detector is used.
e. The mobile phase’s boiling point should not be too low, otherwise bubbles may easily arise and the experiment cannot be carried out.
f. It must be degassed, after the preparation of the mobile phase. Removal of the trace gas dissolved in the mobile phase is not only beneficial for detection but also prevents the trace oxygen in the mobile phase from interacting with the sample. The removal of trace gases dissolved in the mobile phase has many advantages, such as better detection and prevention of trace oxygen from interacting with the sample.
3. Selection of mobile phase flow rate
As the column efficiency is a function of the linear flow rate of the mobile phase in the column, different column efficiencies can be obtained by using different flow rates. For a FLASH column, it is necessary to pursue column efficiency and use the best flow rate. The flow rate is generally 1ml/min, for an inner diameter of 4.6mm column. The flow rate of 0.8ml/min is better, for the inner diameter of 4.0mm column.
To sum up, before the use of FLASH column, bear the followings in mind:
1. Determine the purpose of separation. Determine whether your application requires high resolution, short analysis time, high sensitivity, long column life, low operating costs, and so on.
2. Evaluate the chemical properties of the analyte, such as chemical structure, solubility, stability, etc.
3. Select the appropriate column to understand the physical and chemical properties of the chromatographic packing.