How to clean gas chromatograph detector

How to clean the detector of gas chromatograph

in the process of chromatographic operation, the detector is sometimes contaminated by the loss of stationary phase and the effect of high boiling point components, easily decomposed and corrosive substances in the sample, so that it cannot work normally. Therefore, the problem of how to clean the detector is put forward. If the contaminated substances are limited to high boiling point components, the detector can usually be heated to the maximum operating temperature, which can be removed by not only closely following the imported technical specifications, but also by introducing carrier gas. It is very important to be careful when using the calibrator with radioactive source. For example, the electron capture calibrator usually made of tritium source should not exceed 200 degrees. In addition, it should also be noted that the heating temperature should not damage the insulation material of the detector. If the heating method is not suitable, pure acetone and other solutions can also be injected from the injection port (dozens of microliters can be injected each time) for cleaning, which is effective when the contamination degree is light

if none of the above methods can solve the contamination problem, the evaluator should be removed for more thorough cleaning. First, select a suitable solvent, which can not only dissolve the contamination, but also not damage the evaluator. Inject a syringe into the measuring cell for cleaning. If conditions permit, it is more ideal to clean with super generated wave. It should be noted that the cleaned part cannot be touched by hand

I. cleaning of thermal conductivity detector

fill the measuring cell of the calibrator with acetone, ether, decalin and other solvents, soak them for a period of time (about 20 minutes) and then pour them out. Repeat this for many times until the poured solution is relatively clean. When a solvent cannot be used for cleaning, the high boiling point solvent can be used for soaking and cleaning according to the nature of the dirt, and then the low boiling point solvent can be used for repeated cleaning. Heat after cleaning. Some enterprises are also engaged in 3D printing. Silica gel is removed from the solvent, installed on the instrument, heated the detector, and washed with full carrier gas for several hours before use

II. Cleaning of hydrogen flame ionization detector

when the contamination is not too serious, it is not necessary to remove the chromatographic column for cleaning. At this time, it is only necessary to remove the chromatographic column, connect the sample inlet with the detector with a tube, then pass the carrier gas and raise the temperature of the detector furnace to more than 120 degrees, inject about 20 μ l of distilled water from the sample inlet, and then clean it with dozens of μ l of acetone or Freon (freon113, etc.) solvent. Keep it at this temperature for 1-2 hours to check whether the baseline is stable. If it is still unsatisfactory, repeat the above operations or remove it for cleaning

when the contamination is serious, it must be removed for cleaning. First remove the collector, cathode, nozzle, etc. if the nozzle is made of quartz material, first immerse it in water 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, and then with appropriate solvent (immersion, such as methanol and benzene 1:1), or it can be cleaned with ultrasonic, and finally cleaned with methanol and placed in the oven for drying. Pay attention not to use solvents containing halogen (such as chloroform, dichloromethane, etc.). In order to avoid the interaction with polytetrafluoroethylene materials, resulting in increased noise

after cleaning, all parts should be taken out with tweezers. Do not touch them with your hands. Be careful when assembling after drying, otherwise it will be contaminated again. After the instrument is installed, the carrier gas shall be supplied for 30 minutes, and then the ignition shall be carried out to raise the temperature of the detection room. It is best to keep it at 120 ℃ for several hours before rising to the working temperature

III. cleaning of electron capture detector

there is a radioactive source in the electron capture detector, usually ni63, so you should be particularly careful

first disassemble the foil with radioactive source in the detector, and then wash the metal and PTFE parts of the detector with 2:1:4 sulfuric acid, nitric acid and aqueous solution. When the cleaning solution is clean, clean it with distilled water, then wash it with acetone, and then dry it in an oven at about 100 ℃. For H3 source foil, first wash it with hexane or pentane, never with water. Waste liquid should be diluted with a large amount of water and discarded. Be more careful with ni63 source, never contact with skin, and only operate with long tweezers. First, rinse with ethyl acetate plus sodium carbonate or benzene, then soak in boiling water for 5 minutes, take it out and dry it, and put it into the identifier. Fill the instrument with carrier gas for 30 minutes, then rise to the operating temperature, and standby after a few hours. The remaining waste liquid from cleaning can only be discarded after being diluted with a large amount of water

generally, it cannot be disassembled for cleaning, because there is a risk of radioactive sources. Although it's OK to leave 10cm away

generally, the

thermal cleaning method is used: that is, the high-temperature baking degree of the detector

hot water steam method: after connecting the upper column, the detector rises to high temperature, and each time the water enters UL, times

hydrogen baking method: the carrier gas is replaced by hydrogen, the flow rate is ml/min, and the three items of detector baking h

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