How Hot Is TOO Hot - Part 2

For gas chromatographers, dealing with high temperatures is normal. One of the most frequent questions we receive from customers is: What is the maximum temperature a GC column can reach? In this technical tip, we will take a step back and clarify it from the basics.

All columns have a specific temperature range within which they are stable and functional for extended periods of time, depending on the stationary phase, the material of the capillary tubing used, and the film thickness. Usually, the temperature limits are printed on the box, the metal label on the cage of the column, or they are reported on the QC certificate. If you are not able to find them and you are not sure what the temperature limits of your column are, please reach out to your technical sales consultant. Please note: exceeding the temperature limits might lead to permanent damage to the column and loss of performance.

The maximum temperature is usually made up of two numbers (e.g. 340/360 °C). Sometimes, there may be a single value. The lower temperature is called the maximum isothermal temperature. This is the highest temperature that the column can be exposed to for an extended period. The higher temperature is called the maximum program temperature. The column can be left at this temperature for approximately 10 minutes. After the column is exposed to excessive temperatures, the degree of performance loss is dependent on the temperature, the duration of the exposure, the stationary phase, and the amount of oxygen in the carrier gas. Greater damage occurs with longer exposure times, larger temperature excesses, higher oxygen concentrations, and a lack of carrier gas flow.

Within the maximum temperature limits, columns usually also have a minimum temperature limit (e.g - 60 °C). Below the minimum temperature, the stationary phase loses its chromatographic properties, broadening peaks. However, there is no permanent damage; peaks regain their shape when the column is heated back above the lower temperature limit. Cryocooling a column to focus a sample at the front of the column does not damage a column. Still, columns below their minimum temperatures may be more brittle, so they should be handled with care.