During the chromatographic operation, the identification device is sometimes contaminated by the loss of stationary phase and the action of high boiling point components, easily decomposed and corrosive substances in the sample, which makes it unable to function properly. Therefore, the question of how to clean the identification device has been raised. If the contaminated substance is composed of high boiling point components, it can usually be removed by heating the identification device to the highest operating temperature and then introducing a carrier gas. When using a detector with a radioactive source, extra caution should be taken when heating. For example, electron capture detectors typically made with tritium sources should not exceed 200 degrees Celsius. In addition, attention should be paid to heating at a temperature that does not damage the insulation material of the detector.

If heating method is not suitable, pure acetone or other solutions can also be injected from the injection port (several tens of microliters can be injected each time) for cleaning, which is effective when the degree of contamination is light.

If none of the above methods can solve the problem of contamination, the identification device should be removed for more thorough cleaning. First, choose a suitable solvent that can dissolve the contamination without damaging the identification device. Inject a syringe into the measuring cell for cleaning. If possible, it would be more ideal to use ultrasonic waves for cleaning. It should be noted that the cleaned parts cannot be touched by hand.

1、 Cleaning of heat conduction detector

Fill the measuring cell of the analyzer with solvents such as acetone, ether, and decalin, soak for a period of time (about 20 minutes), and then pour out. Repeat this process multiple times until the poured solution is relatively clean.

When a solvent cannot be used for cleaning, a high boiling point solvent can be used for soaking and cleaning according to the nature of the dirt, and then a low boiling point solvent can be used for repeated cleaning. After washing, heat to remove the solvent, then install it on the instrument, heat the detector, and rinse with gas for several hours before use.

2、 Cleaning of hydrogen flame ionization detector

When the contamination is not too severe, there is no need to remove and clean. At this time, simply remove the chromatography column, connect the injection port to the analyzer with a tube, and then pass gas and raise the analyzer furnace temperature to above 120 degrees. Inject about 20 microliters of distilled water from the injection port first, and then clean it with tens of microliters of acetone or Freon (Freon113, etc.) solvent. Maintain at this temperature for 1-2 hours to check if the baseline is stable. If not satisfied, repeat the above operation or remove the cleaning.

When the contamination is severe, it must be removed for cleaning. First, remove the collection electrode, positive electrode, nozzle, etc. If the nozzle is made of quartz material, soak it in water overnight. If the nozzle is made of stainless steel or other materials, it can be carefully sanded with fine sandpaper (300-400 #) together with the electrode, then soaked in a suitable solvent (such as methanol and benzene 1:1), or cleaned with ultrasonic waves. Finally, it can be washed with methanol and dried in an oven. Be careful not to use solvents containing halogens (such as dichloromethane, etc.). To avoid interaction with polytetrafluoroethylene material and increase noise.

After cleaning, use tweezers to pick up each component and do not touch it with your hands. Be careful when assembling after drying, otherwise it may become contaminated again. After installing the instrument, first introduce the carrier gas for 30 minutes, then ignite and raise the temperature of the detection chamber. First, maintain it at 120 degrees Celsius for several hours, and then raise it to the working temperature.

3、 Cleaning of Electronic Capture Detector

There is a radioactive source in the electronic capture detector, usually H3 or Ni63, so special care should be taken.

First, dismantle the foil containing the radioactive source in the detector, and then wash the metal and PTFE parts of the detector with a 2:1:4 solution of sulfuric acid, nitric acid, and water.

When the cleaning solution is clean, rinse with distilled water, then rinse with acetone, and dry in an oven at around 100 degrees Celsius. For H3 source foil, rinse with hexane or pentane first, never with water. Waste liquid needs to be diluted with a large amount of water and discarded. Be even more careful when dealing with Ni63 sources, never let them come into contact with the skin, and only use long tweezers for operation. First rinse with ethyl acetate and sodium carbonate or rinse with benzene, then soak in boiling water for 5 minutes, take out and dry, and put into the identification device. After installing the instrument, fill it with carrier gas for 30 minutes, then raise it to operating temperature, and wait for a few hours for backup.

The remaining waste liquid needs to be diluted with a large amount of water before being discarded.