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How to clean the detector
During the chromatographic operation, the detector is sometimes contaminated by the loss of stationary phase and high boiling point components, easily decomposed and corrosive substances in the sample, so that it cannot work normally, so the question of how to clean the detector is raised. If the contaminated material is limited to high-boiling components, the detector can usually be heated to the highest temperature and then purged with carrier gas to remove it. When using a detector with a radioactive source, care should be taken when heating. For example, an electron capture detector usually made of tritium source should not exceed 200 degrees. In addition, it should be noted that the temperature of heating cannot damage the insulating material of the detector. If the heating method is not suitable, you can also use pure acetone and other solutions from the injection port (each can be injected dozens of microliters) 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 appraisal should be removed for more thorough cleaning. First, a suitable solvent should be selected. To dissolve the contaminants and not damage the appraisal, inject it into the measuring cell for cleaning. If there are conditions, it is more ideal to use ultrasonic wave cleaning. It should be noted that the cleaned parts cannot be touched by hand.
1. Cleaning of thermal conductivity detector,
Fill the measuring cell of the calibrator with solvents such as acetone, ether, decahydronaphthalene, etc., soak for a period of time (about 20 minutes) and then pour out. Repeat this many times until the poured solution is clean. When a solvent cannot be selected for cleaning, a high-boiling point solvent can be selected for immersion cleaning according to the nature of the contaminant, and then a low-boiling point solvent can be used for repeated cleaning. After washing, heat up to remove the solvent, then install it on the instrument, heat the detector, and flush it with carrier gas for several hours before use.
2. Cleaning of hydrogen flame ionization detector
When the contamination is not serious, you do not need to remove the cleaning. At this time, you only need to remove the chromatographic column, use a tube to connect the inlet to the detector, and then pass the carrier gas to raise the temperature of the detector furnace. At temperatures above 120 degrees, first inject about 20 microliters of distilled water from the inlet, and then wash with dozens of microliters of acetone or Freon (Freon113, etc.) solvent. Keep at this temperature for 1-2 hours to check whether the baseline is stable. If you are still not satisfied, you can repeat the above operation or remove the cleaning.
When the contamination is serious, it must be removed for cleaning. First remove the collector, positive electrode, nozzle, etc. If the nozzle is made of quartz material, first put it in water to soak overnight. If the nozzle is made of stainless steel and other materials, it can be carefully polished with fine sandpaper (300-400 #) together with the electrode, etc., and then used an appropriate solvent (soaked such as methanol and benzene 1: 1), or ultrasonic cleaning, Finally, wash with methanol and dry in an oven. Be careful not to use halogen-containing solvents (such as chloroform, methylene chloride, etc.). So as not to interact with the PTFE material, resulting in increased noise.
After cleaning, use tweezers to remove the parts, and do not touch them. Be careful when assembling after drying, otherwise it will stain again. After the instrument is installed, the carrier gas is passed for 30 minutes, and then the temperature of the detection chamber is increased by ignition. It is best to keep it at 120 degrees for several hours before raising it to the working temperature.
3. Cleaning of the electronic capture detector
There is a radioactive source in the electronic capture detector, usually Ni63, so special care should be taken.
First disassemble the detector with the radioactive source foil, and then wash the metal and polytetrafluoroethylene parts of the detector with 2: 1: 4 sulfuric acid, nitric acid and aqueous solution. When the cleaning solution is clean, wash with distilled water, then wash with acetone, and then dry in an oven at about 100 degrees. For H3 source foil, rinse with hexane or pentane first, and never with water. The waste liquid should be diluted with a large amount of water and discarded. The Ni63 source should be more careful, never contact with the skin, and can only be operated with long tweezers. First rinse with ethyl acetate and sodium carbonate or with benzene, then soak in boiling water for 5 minutes, take out and dry, and put it into the identifier. After loading the instrument, the carrier gas was ventilated for 30 minutes, and then raised to the operating temperature, and then used for a few hours. The remaining waste liquid after washing must be diluted with a large amount of water before being discarded.
ECD Ni63 cannot be disassembled and cleaned because of the danger of radioactive sources. Although it is enough to leave 10cm.
Generally used
1) Thermal cleaning method: that is, the detector is baked at a high temperature of 300-350 degrees
2) Hot water vapor method: the detector is raised to a high temperature of 300-350 degrees after being connected to an empty column, and the water intake is 10-15uL each time, 50-100 times
3) Hydrogen baking method: the carrier gas is replaced with hydrogen, the flow rate is 30-40ml / min, the detector 300-350 is baked for 18-24h
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