Gas Column / Meteorological Column Maintenance

The main goal of column maintenance is to obtain the optimal performance and longest life of the capillary column, rather than simply following the maintenance items in the scheduled maintenance schedule. This depends on the selection of the appropriate column, proper installation / system settings, and avoiding the main factors that cause the degradation of the column performance (fracture, thermal damage, oxidative damage, chemical damage, and contamination). Chromatographic column selection Choose the column that provides the best life
Use as low a bleed column as possible to choose the lowest polarity column that provides the best resolution for most difficult-to-separate samples. When isomer separation is required, use a more polar stationary phase (select only when necessary A more polar stationary phase, but try to use the least polar column that can meet the separation requirements) Use the most suitable column size that can both complete the required separation and optimize the temperature range.

Column installation and setup The first step to optimize column performance and life is to install it correctly. Choose a column size and packing material suitable for the column, inlet, and detector type. Avoid reusing seals. Use a suitable post cutting tool. For example: ceramic sheet or diamond cutter. Install the column before the inlet and detector, making sure the column port is clean and flat. According to the GC manufacturer's specifications, insert the chromatographic column into the inlet and detector at an appropriate distance. The column must be placed on the column holder, and no part of the capillary column can touch the wall of the oven. Before the oven is heated, make sure that all joints are leak-free and that the carrier gas does not contain oxygen.

Reasons for performance degradation:
Column break
Maintenance of Gas Chromatography Column / Meteorological Chromatography Column As long as there are minimal scratches or the polyimide protective layer is damaged, the fused silica column will break. The continuous heating and cooling of the oven, the vibration caused by the oven fan, and the winding on the round column rack will exert stress on the column tube. Under the continuous action of these stresses, cracks will appear until fracture occurs. Note: Large-diameter columns (inner diameter 0.45-0.53mm) are more likely to break.

Avoid breaking. Do not let the column touch sharp edges. For example: column holders and labels, the metal edges of the GC oven, and other items on the column cutter test bench to avoid scratches and damage.

Avoid winding or bending the column too tightly. Recovery If the maintenance of a broken GC / Meteorological column has been heated, it is likely that the stationary phase has been destroyed. Discard the broken column (the one without carrier gas), cut 6 inches from the end of the column, and install it. If the broken column is not heated, use a small volume joint to connect the two columns.

For the maintenance of a gas chromatography column / weather column, the number of connectors must not exceed 2-3. Exceeding the maximum temperature limit of the gas chromatography column / weather column will accelerate the degradation of the stationary phase and the tube surface. This will lead to premature column bleed, peak tailing of active compounds and / or decreased column efficiency (decreased resolution). Do not exceed the specified upper limit of column temperature. ——Isothermal upper limit: the temperature that the column can withstand indefinitely.

——Programmed temperature limit: the highest column temperature; the chromatographic column can only work at this temperature for 5-10 minutes. Set the GC maximum oven temperature to the upper limit of the column temperature or a few degrees higher. If there are two columns in the oven, make sure that the highest oven temperature is set to the upper temperature limit of the column with the lowest upper temperature limit. Resume removing the column from the detector. Heat the column for 8-16 hours at the isothermal upper limit temperature. Cut off 10-15 cm from the end of the column. Reinstall the column on the detector and age under normal conditions.

● Note: Thermal damage is irreversible. Columns cannot usually be restored to their original performance; however, the columns are still usable. After thermal damage, the life of the column will be shortened.