Gas chromatography often runs 24 hours due to the need for continuous production. It is difficult to have the opportunity to systematically clean and maintain the instrument. Once there is a suitable opportunity, it is necessary to thoroughly clean and maintain the key components of the instrument as much as possible according to the actual operation of the instrument.
Gas chromatograph is often used for the quantitative analysis of organic matter. After the instrument is running for a period of time, due to static electricity, the inside of the instrument is easy to absorb more dust. In addition to the accumulation of dust in the circuit board and circuit board socket, it is often associated with certain organic The vapors are adsorbed together; because the freezing point of some organic substances is low, the solidified organic matter is often found at the inlet position. After the use of the splitting line for a period of time, the inner diameter becomes finer and even blocked by organic matter; during use, the TCD detector is very It is likely to be contaminated by organic matter; the FID detector is used for organic analysis for a long time, organic matter is deposited at the nozzle or collector position, or the nozzle and collector portion of carbon deposits often occur.
1. Purging and cleaning inside the instrument
After the gas chromatograph is stopped, open the side and rear panels of the instrument, and use the instrument air or nitrogen to purify the dust inside the instrument, and use a soft brush to handle the dusty or not easy to clean place. After the purge is completed, scrub the water or organic solvent in the place where the organic matter is contaminated inside the instrument. The water-soluble organic matter can be wiped with water first, and the organic solvent can be used for the place that cannot be thoroughly cleaned. It is not water-soluble or possible. The organic substance that chemically reacts with water is cleaned with an organic solvent that does not react with it, such as toluene, acetone, carbon tetrachloride, and the like. Note that corrosion or secondary contamination of the instrument surface or other components may not occur during the wiping of the instrument.
2, circuit board maintenance and cleaning
Before the gas chromatograph is ready for maintenance, turn off the power of the instrument. First, purge the circuit board and the board slot with the instrument air or nitrogen. Use a soft brush to clean the dusty parts of the circuit board and the slot. Clean it up carefully. Wear gloves as much as possible during operation to prevent static electricity or sweat on your hands from affecting some components on the board.
After the purge is completed, the board should be carefully observed to see if the printed circuit board or electronic components are significantly corroded. Wipe the electronic components and printed circuits contaminated with organic materials on the board with absorbent cotton, and wipe the board interface and the socket.
3, the cleaning of the inlet
During the inspection, it is necessary to clean the glass liner, the split plate, the inlet line of the inlet, and the EPC.
Cleaning of the glass liner and the splitter plate: Carefully remove the glass liner from the instrument and carefully remove the glass wool and other impurities from the liner with tweezers or other small tools. Do not scratch the liner surface during the removal process.
If conditions permit, the initially cleaned glass liner can be cleaned with ultrasonic waves in an organic solvent and dried for use. It can also be directly washed with an organic solvent such as acetone or toluene, and dried after use.
The most ideal cleaning method for the split plate is to sonicate in the solvent and use it after drying. It is also possible to select a suitable organic solvent for cleaning: after the split plate is taken out from the inlet, it is first washed with an inert solvent such as toluene, then with an alcohol solvent such as methanol, and dried.
Cleaning of the split line: When the gas chromatograph is used for the analysis of organic matter and polymer compounds, the freezing point of many organic substances is low, and some organic substances are solidified in the split line during the process of venting the sample from the gasification chamber through the split line.
After a long period of use of the gas chromatograph, the inner diameter of the split line gradually becomes smaller or even completely blocked. After the split line is blocked, the instrument inlet shows abnormal pressure, the peak shape deteriorates, and the analysis result is abnormal. During the overhaul process, the split line needs to be cleaned regardless of whether it is possible to determine whether the split line is blocked or not. The cleaning of the split pipeline generally selects organic solvents such as acetone and toluene. It is difficult to clean the shunt pipeline with severe blockage by simple cleaning, and some other auxiliary mechanical methods are needed to complete. The shunt line can be simply unblocked by selecting a wire with a suitable thickness, and then washed with an organic solvent such as acetone or toluene. Since it is not easy to make an accurate judgment on the condition of the diverting portion in advance, it is necessary for the hand-separated gas chromatograph to clean the shunt line during the overhaul process.
For EPC controlled split gas chromatographs, due to long-term use, it is possible to make some small sample inserts into the EPC and gas pipeline interface, which may cause blockage or change of inlet pressure at any time. Therefore, each time the inspection process is carried out, the EPC part of the instrument is inspected and cleaned with an organic solvent such as toluene or acetone, and then dried.
Due to injection and other reasons, some of the organic matter may be formed at the outside of the inlet at any time. The absorbent body may be used to take a preliminary wipe of the inlet with acetone, toluene, etc., and then the organic matter that cannot be wiped off is mechanically removed. Be careful to remove the solidified organic matter and do not damage the instrument components. After the solidified organic matter is removed, the instrument parts are carefully wiped with an organic solvent.
4. Cleaning of TCD and FID detectors
The TCD detector may be contaminated by deposits from the column or other substances entrained in the sample during use. Once the TCD detector is contaminated, the instrument’s baseline exhibits jitter and increased noise. It is necessary to clean the detector.
HP’s TCD detector can be hot-cleaned. The specific method is as follows: turn off the detector, remove the column from the detector connector, block the connector of the detector in the oven with a dead block, and set the flow rate of the reference gas. To 20 ~ 30ml / min, set the detector temperature to 400 ° C, hot cleaning 4 ~ 8h, can be used after cooling.
The following methods can be used for domestic or Nissan TCD detector contamination. After the instrument is stopped, remove the gas inlet of the TCD, and sequentially inject acetone (or toluene, depending on the chemical nature of the sample) with anhydrous ethanol and distilled water from the inlet port 5 to 10 times with a 50 ml syringe. Slowly blow the air from the air inlet with the ball, blow out the impurities and residual liquid, and then re-install the air inlet connector. After the power is turned on, raise the temperature of the column to 200 ° C, the temperature of the detector rises to 250 ° C, and the ratio is analyzed. The carrier gas is 1 to 2 times larger than the carrier gas until the baseline is stable.
For serious pollution, the gas outlet can be blocked with dead plugs. Fill the inlet with acetone (or toluene, depending on the chemical nature of the sample), keep it for about 8h, drain the waste, and then treat it as above. .
FID detector cleaning: FID detector has good stability in use, relatively low requirements for use, and is common in use. However, during long-term use, problems such as detector nozzle and collector carbon deposit are likely to occur, or organic matter is present. Deposition of the nozzle or collector. For problems such as FID deposits or organic deposits, the detector nozzle and collector can be cleaned with an organic solvent such as acetone, toluene or methanol. When the carbon deposit is thick and cannot be cleaned, the thicker part of the detector can be carefully sanded with fine sandpaper. Be careful not to damage the detector during the grinding process. After the initial grinding is completed, the contaminated part is further wiped with a soft cloth, and then the organic solvent is finally used for cleaning, which is generally eliminated.
