What details should be paid attention to when the chromatogr

01 so what conditions need to be aged?
1. Newly purchased chromatographic column: for the new chromatographic column, the unstable stationary liquid in the column or the residual solvent in the filling column can be removed by aging treatment before the first use, so as to ensure the stability of the performance of the new column.
2. Chromatographic column that has not been used for a long time but has to be used again: through the aging of the chromatographic column, the pollutants, oxygen and trace water that have been put into the chromatographic column for a long time can be removed, and the performance of the chromatographic column can be restored.
3. Long term used chromatographic column or chromatographic column with complex matrix and large amount of sample analysis: in this case, the residual high boiling point impurities and pollutants in the chromatographic column are mainly removed by aging; on the other hand, the long-term high-temperature use of chromatographic column will cause the loss of stationary liquid, exposing some active sites. Through aging treatment, taking advantage of the characteristics of thermal expansion and cold contraction of the stationary phase, it is possible to remove the high boiling point impurities and pollutants in the chromatographic column In order to cover the active sites on the inner wall of the column, the performance of the column was restored.
02 how to age and what details should be paid attention to during aging?
1. Selection of aging temperature
In general, the aging temperature is controlled between the analytical temperature of method Z and the upper limit of constant temperature of chromatographic column.
The aging temperature can also be set as 20-30 ℃ lower than the upper limit of constant temperature of chromatographic column, or 20-30 ℃ higher than that of method Z.
It should be noted that each gas column has a temperature limit that it can withstand. Before aging, it is necessary to read the packing box or instruction manual carefully. In the aging process, once the temperature limit of chromatographic column is exceeded, the stationary phase will be lost and the service life will be shortened. Therefore, the requirement of aging temperature is to ensure the removal of impurities and pollutants, the lower the temperature, the better.
2. Aging time
The specific aging process is generally set as temperature programmed (slowly heating to the set aging temperature), for example, the initial temperature is 35 ℃, 2-5 ℃ / min, the temperature is raised to the aging temperature and kept for 0.5-2 h. The specific aging time can be determined according to the impurity removal effect.
3. Prevent oxygen from entering the column
Under high temperature conditions, with the presence of oxygen, the stationary liquid is easy to be oxidized, and the stable silane bond will be broken, which will cause serious column loss and decrease of column efficiency.
Therefore, in order to avoid oxygen entering the chromatographic column, the following points should be paid attention to:
Connect the gas inlet end of the chromatographic column with the injection port of the instrument, place the end of the chromatographic column in alcohol, carry the gas, and observe whether there are continuous bubbles. If not, it is necessary to check whether the column is broken in the middle, whether the installation is firm, and whether the system is leaking.
Set the carrier gas flow rate to the normal working value, set the injection port, column temperature box and detector (if connected to the detector) to 35 ℃, or turn off the instrument temperature control system, and pass the carrier gas for 15-30 min at room temperature to replace the possible oxygen in the instrument system and chromatographic column.
● ensure that the other joints of the instrument are properly installed and leak checked.
4. Avoid pollution
In general, in order to avoid contamination of the detector, it is not recommended to connect the detector during aging. The conventional operation is to block the lower end of the detector with a solid pressure ring and turn off the temperature. If the detector is connected, there is no need to ignite the FID detector, and it is not necessary to switch on the air and hydrogen; if it is an ECD detector, it is necessary to set the tail gas to avoid excessive heat and temperature transfer to the ECD, so as to ensure the safety of the internal radiation source of the detector. In addition, it is forbidden to use hydrogen to age the chromatographic column to avoid explosion due to hydrogen leakage and accumulation in the column temperature box.
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5. Maintenance is required before aging
For long-term used chromatographic columns or chromatographic columns with complex matrix and large sample analysis, aging is to remove some residual pollutants. These pollutants generally belong to compounds with high boiling point, which often gather in the column head, such as proteins, pigments, colloids and so on. In order to avoid the contaminant in the column head transferring to the internal part of the column, but not completely discharged from the column, the column should be cut before aging, and a part of the column should be cut off appropriately. In addition, the injection port liner, quartz cotton and injection septum should be maintained to avoid secondary pollution to the chromatographic column during aging. Generally speaking, it is meaningful to remove the pollution source and then aging the chromatographic column.