During the chromatographic operation, the evaluator is sometimes contaminated by the loss of the stationary phase and the high boiling point components of the sample, which are easily decomposed and corrosive.
As a result, the work cannot be performed normally, and thus the problem of how to clean the identifier is raised. If the contaminated material is limited to high-boiling components, the identifier can usually be removed by heating the detector to the maximum use temperature and then passing the carrier gas. Care should be taken when heating with an evaluator with a radioactive source. For example, an electron capture evaluator usually made of cesium is generally not more than 200 degrees. In addition, it should be noted that the temperature of the heating does not damage the insulation of the evaluator.
If it is not suitable to use the heating method, it may be washed by injecting a solution such as pure acetone from the injection port (injecting several tens of microliters each time), which is effective when the degree of contamination is light.
If none of the above methods can solve the contamination problem, the identifier should be removed for thorough cleaning. First, select the appropriate solvent. It is necessary to dissolve the contaminant and not damage the identifier. Inject the syringe into the measuring cell for cleaning. If conditions are met, it is more desirable to use ultra-wave cleaning. It should be noted that the cleaning part cannot be touched by hand.
First, the cleaning of the heat conduction detector
A solvent such as acetone, diethyl ether or decalin is filled in the measuring cell of the applicator, soaked for a period of time (about 20 minutes) and then poured out, and this is repeated several times until the poured solution is relatively clean.
When a solvent cannot be used for washing, the high boiling point solvent may be used for immersion cleaning according to the nature of the contaminant, and then repeatedly washed with a low boiling point solvent. After washing, heat to remove the solvent, then put it on the instrument, heat the detector, and use it after a few hours of carrier gas flushing.
Second, the cleaning of the hydrogen flame ionization detector
When the contamination is not serious, you don't need to remove the cleaning. In this case, you only need to remove the column, connect the inlet to the appraisor with a tube, then pass the carrier gas and the temperature of the detector. When it is raised to 120 degrees or more, inject 20 ml of distilled water from the inlet first, and then wash with tens of microliters of acetone or Freon (Freon 113, etc.) solvent. Check at this temperature for 1-2 hours to check if the baseline is stable. If you are still not satisfied, repeat the above operation or remove the cleaning.
When the stain is severe, the cleaning must be removed. First remove the collector, positive electrode, nozzle, etc. If the nozzle is made of quartz material, first place it in water for soaking overnight. If the nozzle is made of stainless steel or the like, it can be carefully ground with a fine sandpaper (300-400#), and then with a suitable solvent (soaked with methanol and benzene 1:1), or ultrasonically. Finally, it was washed with methanol and placed in an oven for drying. Be careful not to use halogen-containing solvents (such as chloroform, dichloromethane, etc.). In order to avoid interaction with PTFE materials, resulting in increased noise.
After washing, the parts should be taken with tweezers and not touched by hand. Be careful when assembling after drying, otherwise it will stain again. After loading the instrument, first carry the carrier gas for 30 minutes, and then raise the temperature of the detection chamber by igniting. It is best to hold it at 120 degrees for several hours before rising to the working temperature.
Third, the cleaning of the electronic capture detector
There is a source of radiation in the electron capture detector, usually H3 or Ni63, so be careful.
First remove the source foil from the appraisator, then wash the metal and Teflon portion of the detector with 2:1:4 sulfuric acid, nitric acid and an aqueous solution.
When the cleaning solution is clean, wash it with distilled water, then wash it with acetone, and then dry it in an oven of about 100 degrees.
For H3 source foil, rinse with hexane or pentane and never wash with water. The waste liquid should be diluted with a large amount of water and discarded.
Care should be taken with the Ni63 source, never in contact with the skin, and only with long tweezers. First rinse with ethyl acetate plus sodium carbonate or rinse with benzene, then soak for 5 minutes in boiling water, remove and dry, and put into the appraisal. After loading the instrument, carry the carrier gas for 30 minutes, then increase to the operating temperature, and wait for a few hours. The remaining waste liquid should be diluted with a large amount of water before it can be discarded.
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