How to carry out cleaning and maintenance of gas chromatograph?

Gas chromatograph is often used for the quantitative analysis of organic substances. After the instrument is operated for a period of time, due to static electricity, the inside of the instrument is likely to absorb more dust; the circuit board and the circuit board socket are often and some organic The vapors are adsorbed together; because the freezing point of some organics is low, solidified organics are often found at the injection port. After a certain period of time, the diverting line becomes thinner and even blocked by organic substances. During use, the TCD detector is very It may be contaminated with organic matter; FID detectors are used for organic analysis for a long time, deposition of organics at the nozzle or collector site or nozzles, and coking of collector parts often occur.

1Inside the instrument, purge and clean. After the gas chromatograph is shut down, open the side and rear panel of the instrument and use instrument air or nitrogen to sweep the dust inside the instrument. Use soft hair on places where there is more dust or where it is not easy to purge. Brush with processing. After the purging is completed, scrubbing with water or organic solvents in the area where the organic substances are contaminated in the instrument can be performed by wiping the water-soluble organic materials with water. If the organic solvent can not be thoroughly cleaned, the organic solvent can be used for treatment. It is not water-soluble or possible. Organic chemicals that react with water are cleaned with organic solvents that do not react with them, such as toluene, acetone, and carbon tetrachloride. Note that the instrument surface or other components cannot be corroded or recontaminated during wiping.

2 Maintenance and Cleaning of the Circuit Board Before the gas chromatograph is ready to be overhauled, cut off the power supply of the instrument and first use instrument air or nitrogen to purge the circuit board and circuit board slots. Use a soft brush to clean the circuit board and slot when blowing. The more dusty parts are carefully cleaned. Wear gloves as much as possible during the operation to prevent static electricity or perspiration on hands from affecting some components on the circuit board.

After the purge work is completed, the use of the circuit board should be carefully observed to see if the printed circuit board or electronic components are significantly corroded. The electronic components contaminated with organic substances on the circuit board and the printed circuit are carefully wiped with alcohol-absorbent cotton, and the circuit board interface and slot portion are also wiped.

3. Injector Cleaning During the inspection, it is necessary to clean the glass liners, splitter plates of the gas chromatograph inlet, the diverter line of the inlet, EPC and other components.

Glass Liner and Diverter Plate Cleaning: Carefully remove the glass liner from the instrument and carefully remove the glass wool and other contaminants from the liner with tweezers or other small tools. Do not scratch the liner surface during removal.

If conditions permit, the pre-cleared glass liner can be ultrasonically cleaned in organic solvents and used after drying. It can also be cleaned directly with organic solvents such as acetone and toluene, and can be used after drying after cleaning.

The best cleaning method for the shunt plate is to use ultrasonic treatment in the solvent and use after drying. You can also choose a suitable organic solvent cleaning: After removing the shunt plate from the injection port, first wash with an inert solvent such as toluene, then wash with an alcohol solvent such as methanol, and use after drying.

Diversion line cleaning: When the gas chromatograph is used to analyze organics and macromolecules, many organics have a low freezing point. During the process of venting the sample from the gasification chamber through the diversion line, some of the organics solidify in the diversion line.

After a long period of use of the gas chromatograph, the inner diameter of the diverting line gradually becomes smaller or even completely blocked. After the flow of the bypass line is blocked, the instrument inlet shows an abnormal pressure and the peak shape is degraded. The analysis result is abnormal. During the inspection process, it is necessary to clean the diverter line no matter whether it can determine whether the diversion line has clogging. Diversion line cleaning generally chooses acetone, toluene and other organic solvents. It is difficult to clean the severely diverted pipelines with a simple cleaning method. Some other auxiliary mechanical methods are required to complete the diversion line. You can choose the appropriate thickness of steel wire to carry out simple dredging, and then use acetone, toluene and other organic solvents for cleaning. Due to the fact that it is not easy to make accurate judgments on the diversion part in advance, it is necessary for the manual diverter gas chromatograph to clean the diverter line during the inspection process.

For gas chromatographs with EPC-controlled shunts, due to prolonged use, it is possible that some small sample swarf will enter the interface between the EPC and the gas line, which may cause blockage of the EPC section or pressure changes in the inlet port at any time. Therefore, the EPC part of the instrument should be checked as far as possible during each maintenance process, and cleaned with organic solvents such as toluene and acetone, and then dried.

Due to sample injection and other reasons, the external part of the injection port may form some organic condensation at any time. The organic solvent such as acetone, toluene, etc. can be used for the preliminary wipe of the injection port, and then the organic substances that cannot be wiped off can be removed mechanically. Care must be taken in the removal of solidified organics. Do not damage the parts of the instrument. After the solidified organics are removed, the parts of the instrument are carefully wiped with organic solvents.

4. Cleaning of TCD and FID detectors TCD detectors may be contaminated with deposits from the column or other substances entrained in the sample during use. Once the TCD detector is contaminated, the instrument's baseline jitter and noise increase. It is necessary to clean the detector.

HP's TCD detector can be used for thermal cleaning methods. The specific method is as follows: Close the detector, remove the column from the detector connector, and block the connector of the detector inside the oven with dead plug, set the reference gas flow rate. To 20 ~ 30ml/min, set the detector temperature to 400 °C, heat cleaning 4 ~ 8h, after cooling can be used.

Domestic or Nissan TCD detector contamination can be done in the following ways. After the instrument is shut down, remove the inlet of the TCD gas path and use a 50ml syringe to inject acetone (or toluene, depending on the chemical nature of the sample) with ethanol and distilled water from the inlet port for 5 to 10 injections. Use a suction ball to slowly blow air from the air inlet, blow out impurities and residual liquid, and then re-install the air inlet connector. After starting, raise the column temperature to 200°C, and increase the detector temperature to 250°C. The gas flow is 1 to 2 times the carrier gas until the baseline is stable.

For serious pollution, the outlet can be plugged with dead plugs, filled with acetone (or toluene, depending on the chemical nature of the sample) from the air inlet, hold for about 8 hours, discharge waste, and then treated as described above .

Cleaning of the FID detector: The FID detector has good stability in use, relatively low requirements for use, and is generally used, but in the course of prolonged use, problems such as detector nozzles and collector carbon deposits are prone to occur, or organic substances are Deposition at the nozzle or collector. For problems such as deposition of FID carbon deposits or organic substances, the detector nozzles and collectors may be cleaned with organic solvents such as acetone, toluene, and methanol. When the coke is too thick to clean, the thicker part of the detector coke can be carefully ground with fine sandpaper. Be careful not to damage the detector during grinding. After the preliminary polishing is completed, the contaminated portion is further wiped with a soft cloth, and finally cleaned with an organic solvent, which is generally eliminated.