Ways to extend column life

Ways to extend column life

A column should be replaced when it is not ready for use. The concept of “unrecoverable” is not exactly the same in many chromatographers. Some people think that only when the pressure of the column increases to an unacceptable level of the system, consider scrapping, as long as the pressure is within the acceptable range, always try to repair it. To extend the life of the column. It is also possible to change from the analysis of highly demanding samples to the analysis of low-demand samples, from the separation of multi-component samples to the separation of single-component samples, from the separation of complex media samples to the separation of relatively simple media. The most common method used in laboratories to extend column life is to repair the column head, change the stainless steel sintered sheet, rinse, and backflush the column.
Patching the stigma and changing the stainless steel tabs are often associated with each other and have been briefly described above. After removing the filter, it is found that the stigma collapses or the filler is contaminated. The same kind of filler (digging dirty filler) can be used to fill the stigma with anhydrous ethanol, and the flat and smooth stainless steel or PTFE with the same inner diameter of the column is used. The ethylene rod is pressed tightly, filled again, and then compacted, repeated 3 to 5 times. Finally, the column head is wetted several times with absolute ethanol, the filler on the outer wall of the column is cleaned, a new filter is added, the joint is tightened, and the joint is attached. The pump is flushed and then connected to the detector. If the collapse is very deep, or if there is a lot of dirty packing to be dug, fill the column head and then rinse it with the pump for 15 minutes, then remove the column to fill it, then connect the pump to rinse it. Repeating several times can restore most of the efficiency. Sometimes a higher flow rate should be used to be effective.
The repaired column can not be restored to the original efficiency. It has a good effect at the beginning of repairing several times. As the number of repairs increases, it will be repaired for a short time. At the later stage, the bonded phase will be lost with the dissolution of silica gel. Coupled with the corrosion of chemicals, it can no longer be repaired at this time.
For high-priced columns, you must stick to your own hands. If the exclusion column does not change over time, only low separation conditions are required, and a slight repair can solve the problem.
Backflushing columns are also a frequent maintenance measure and do not promote new column backwash columns. The column is used in the middle and late stages, and the reverse recoil is considered after many repairs. The collapse of the plain column head can be flushed in front of the inverted column, or it can be poured back to the column head (original column outlet). The latter effect is better. After the column is used in reverse, the column efficiency loss is large (about 40% to 60%), and it can often be reversed and then poured over. As long as the column bed is not damaged, the effect is not bad. Before inverting the column, check the condition of the sintered filter at both ends of the column to prevent the filter from being sintered (the original column head is subjected to excessive pressure and the packing is pumped out).
The flushing process should be accompanied by the above measures.
There are a few laboratories that install the column themselves, or ask the manufacturer to install the column. The column hardware is the old column used, which saves 50% of the cost, but sometimes it also has some trouble. The inner wall of the column is not re-polished, the column wall effect is relatively large, the resolution is lowered, or the tail peak is peaked. After the column is reassembled, the ferrule is easy to loosen and the entire column head leaks. It can be sealed by means of a Teflon soft film, but it cannot withstand higher pressures.
It is worthwhile to reprocess some columns, but some are worthless. In addition to considering the price, we must also consider the actual work requirements. Any column can be repaired several times, the sample is processed well, the mobile phase is mild, and the pressure is reduced to reduce the number of times the column is repaired. The column is scrapped when the column pressure rises above the limit of the system. Different types of bulk packing (C 18 , silica gel) should be available in the laboratory. It is good to repair the column head with the same type and the same size of filler. If you do not have the required filler on hand, you can replace it with other fillers, which is much better than a column with a stigma collapse.

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