Aging Method and Precautions for HPLC Columns
Aging of HPLC columns is a common task in gas phase applications. The purpose of aging is to remove the stationary phase lost fragments or contaminants on the surface of the stationary phase and prepare the column for the upcoming analysis. Usually, the new column is used for the first time, the column is used again after a period of time, or the column is contaminated or damaged.
HPLC column aging method
The column used at normal temperature can be directly installed on the chromatograph, and the carrier gas can be connected to the baseline to be used. If the column is used under high temperature operating conditions, the carrier gas is passed at a temperature slightly higher than the operating temperature. From a few hours to tens of hours, the volatile substance in the fixative is completely flushed out and can be put into use after the baseline is stable. Different HPLC column aging methods are also different. The specific method is as follows:
1. Capillary column
Make sure that the carrier gas flows through the capillary column for 15-30 minutes.
Slowly temperature programmed (5o/min) to aging temperature.
Initial aging temperature ≥ 4 hours.
If the column is contaminated, the column can be aged at the recommended maximum column temperature of 20 oC.
The recommended aging temperatures are: Tcond = Tmax/2 – Tapp/2 + Tapp, where: Tcond = aging temperature, Tmax = the highest temperature recommended for the column, Tapp = the highest temperature used in the application.
When aging the column, do not connect the capillary to the detector. The end should be emptied and the detector plugged with a stuffy head. If it is an FID, it is allowed to be connected, but the detector temperature should be raised.
2. Packed column
Connect the column to the carrier gas at a flow rate of 5 to 10 ml/min, and aging for 8 to 24 hours at a temperature higher than the use temperature of 5 to 10 °C (but must be lower than the column use limit temperature) in order to remove residual solvent during the column packing. The fixing liquid is evenly distributed to improve the efficiency of the column. The column must be disconnected from the detector during aging to avoid contamination of the detector.
It is generally not necessary to buy a dedicated HPLC column aging chamber, and the HPLC column aging is of course placed in the column oven.
Nitrogen acts as a carrier gas and flows in the chromatographic line. Whether it is an aging column or an analytical experiment, nitrogen is vented to the air. Chromatographic detectors such as FID nozzles are inherently hollow and burn during the test. It is only hydrogen and combustion gas (air or oxygen), and the nitrogen is vented out of the nozzle, so there is no problem of accumulation in the column oven. Also, when the column is aged, neither hydrogen nor air is required because ignition is not required.
However, there is another case. When the detector used is TCD (thermal conductivity detector), hydrogen is generally used as a carrier gas in China. At this time, special attention should be paid. If the air flow path in the column temperature tank leaks, it will It is common for hydrogen to accumulate in the column oven before the explosion of hydrogen in the column oven. So if this is the case, it is recommended to replace the nitrogen into a column or purchase a special aging box for aging.
Precautions for HPLC column aging
The maximum temperature of aging should generally not exceed the upper limit of the temperature of the column. The initial aging can be raised to the maximum temperature of the column (the upper limit of the temperature programmed temperature) for a period of time, recommended not to exceed 10 min; for strong polar columns (such as polyethylene) Alcohol stationary phase), it is recommended to use a slower temperature program, such as 5 °C / min.