I believe that everyone has encountered this kind of situation. When encountering complex matrices, such as oil-containing, protein-containing or Chinese medicinal materials projects, the analytical column is prone to problems such as increased column pressure, poor peak shape, and decreased column efficiency. The cost of directly replacing the analytical column is too high, and it takes too much time to perform abnormal maintenance on the chromatographic column. In this case, a guard column can be installed to prolong the service life of the chromatographic column.
What is the function of the guard column?
First, filter out physical pollution. The HPLC chromatographic system operates under high pressure for a long time, and the sealing gasket will inevitably produce fine physical particles, which will cause permanent blockage at the inlet of the chromatographic column. The guard column can effectively block the damage of particles to the chromatographic column;
Second, delay chemical pollution. The separation of the chromatographic column for the target is mainly the interaction of chemical forces. Depending on the complexity of the target, there will be different strengths of adsorption to the chromatographic column. Strong adsorption on the column bed starts from the injection port and slowly extends in the direction of the mobile phase. The guard column added at the front end of the chromatographic column uses the same packing as the chromatographic column and is well packed. Strong adsorption occurs first on the guard column. By replacing the cartridge regularly, the column can be greatly protected.
The working principle of the guard column is as follows:
A guard cartridge is placed in the cartridge of the guard column, and the cartridge contains packing. These packings can intercept some strong polar, strong acid and strong basic substances in the sample and prevent them from contaminating and damaging the packing in the column. Therefore, using a guard column can protect the chromatographic column in all directions, which is the best way to protect the chromatographic column.
How to choose a suitable guard column?
First, for most analysts, a 1 cm long guard column will provide adequate protection. However, if the sample is very dirty, or it is found that the 1cm guard column needs to be replaced frequently during the work, then the 2cm or 3cm guard column should be used;
Secondly, most people choose the packing of the guard column according to the packing of the analytical column. Under normal circumstances, they can choose the same packing as the analytical column.
Therefore, the principle of choosing a guard column is: under the premise of meeting the requirements of separation and analysis, choose a short guard column sleeve as much as possible, and choose a column core with the same packing as the analytical column.
The guard column also has a service life. When the column pressure rises > 10%, the column efficiency drops > 10%, and the resolution drops > 10%, these all remind us to maintain the guard column.
The maintenance method of the guard column is: mark the column sleeve to confirm the positive and negative directions of the guard column core; remove the guard column and connect the guard column in reverse without opening the ferrule (note that the chromatographic column cannot be connected at this time). ), rinsed with methanol:water=20:80 at a flow rate of 3mL/min for 10min, and then rinsed with pure methanol at a flow rate of 3mL/min for 10min. After flushing, connect the guard column directly, turn on the pump to remove the air in the guard column and the connecting pipe, and then connect the chromatographic column, which can be used normally; if there is no improvement, the guard column core needs to be replaced.
Welch materials currently has independent guard columns, direct-connected guard columns, direct-connected ultra-high pressure guard columns, etc., as well as corresponding guard column cores. Product information is as follows:
In-Line UHPLC Guard Cartridges article number
Freestanding Guard Cartridge Cartridge article number