How to install and debug gas chromatography
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1). Take out the logbook to register users and start time.
2). Open the carrier gas switching valve on the purifier, and then check for leaks to ensure good air tightness.
3). Adjust the total flow to an appropriate value (measured according to the scaled flow meter).
4). Adjust the shunt valve so that the shunt flow is the flow required for the experiment (actually measured with the "SPLIT VENT" on the gas circuit system panel using a soap film flowmeter), and the column flow is the total flow minus the shunt flow.
5). Adjust the makeup flow control valve to make the makeup flow at an appropriate value, and make the sum of makeup flow and column flow not less than the total carrier gas flow.
6). Open the air and hydrogen on-off valve of the purifier and adjust the air and hydrogen flow rate to an appropriate value.
7). Set the column temperature, inlet temperature, and FID detector temperature according to the experimental needs.
8). When the temperature of the FID detector reaches above 150oC, press the FIRE key to ignite the flame of the FID detector.
9). Set FID detector sensitivity and output signal attenuation.
10). If the baseline is not at the zero position, adjust the zero adjustment potentiometer A so that the FID output signal is near the zero position of the recorder or integrator. When the set parameters reach the setting, they can be analyzed.
11). When the set parameters reach the setting, the sample can be analyzed.
Precautions
1). Read the instructions for use in detail before being independently operated by the person in charge.
2). Various gas flow rates can be fixed after groping out the best conditions.
3). Each use of the instrument should be registered in detail.
The installation of a chromatograph
1. Requirements for chromatograph analysis room (1) There must be no strong magnetic field, flammable and strong corrosive gas around the analysis room.
(2) The indoor ambient temperature should be in the range of 5 to 35 degrees, the humidity is less than or equal to 85% (relative humidity), and the indoor air circulation should be maintained. Conditional factories are best equipped with air conditioners.
(3) Prepare a working platform that can withstand the entire set of instruments, has a moderate width and height, and is easy to operate. Generally, a cement platform is preferred in the factory (0.6 to 0.8 meters high). The platform cannot be close to the wall, and should be 0.5 to 1.0 meters away from the wall, which is convenient for wiring and maintenance.
(4) The power line capacity for the instrument should be around 10KVA, and the power supply used by the instrument should not share a line with high-power power-consuming equipment or frequently-changed electrical equipment. The power supply must be well grounded. Generally, an iron rod (wire) with a length of about 0.5 to 1.0 meters is nailed to the wet ground (or salt solution infusion), and then the power supply ground point is connected to it. In short, the grounding resistance should be less than 1 ohm. (Note: It is recommended that both the power supply and the case are grounded, so that the effect is better).
2. Gas source preparation and purification (1) Gas source preparation Prepare high-pressure steel cylinders that require gas in advance (usually available in large and medium-sized cities). Zhuang certain gas cylinders can only contain this gas, the color of each cylinder Represents a gas and cannot be interchanged. Generally, three kinds of gases, nitrogen, hydrogen, and air are used. It is best to prepare two cylinders for each gas for future use. Some plants may use hydrogen generators and air compressors, but the air compressor must be oil-free. When the cylinder pressure drops to 1 ~ 2Mpa, the cylinder should be replaced. Generally, the manufacturer can use 99.99% of the above gas, and the electronic capture detector must use more than 99.999% of the high-purity gas source.
(2) Gas source purification In order to remove the moisture, ash and organic gas components that may be contained in various gases, the gas should be strictly purified before entering the instrument. If all cylinder gas is used, some chromatographs are equipped with purifiers and filled with 5A molecular sieves, activated carbon, silica gel, which can basically meet the requirements. If the general hydrogen generator is used, the purification of water must be strengthened, so the area of ​​the drying tube should be increased (the volume is more than 450 cubic centimeters, the filler is preferably 5A molecular sieve), and the volume is larger after the generator To reduce or overcome the impact of the gas source pressure fluctuation on the instrument baseline. If an air compressor is used as the air source, the air inlet of the air compressor should be strengthened for air filtration and the volume of the purification tube should be increased. The drying tube should be filled with half 5A molecular sieve and half activated carbon. General domestic oil-free gas compressor (made in Tianjin) can meet the needs.
3. After checking the completeness of the chromatograph and placing the instrument out of the box, carry out an item-by-item inventory according to the list of accessories in the data bag, and keep spare parts of vulnerable parts properly. Then place it on the working platform according to the requirements of the instrument's instruction manual, and connect the various parts of the instrument to the wiring diagram and the plugs and sockets, and finally connect the recorder and data processor. Be careful not to misconnect each connector.
4. External gas connection (1) The instrument installed with the pressure reducing valve is equipped with a pressure reducing valve, if not, you must purchase it. Two oxygen valves and one hydrogen pressure reducing valve were used. Install 2 oxygen pressure reducing valves and 1 hydrogen pressure reducing valve to nitrogen, air and hydrogen cylinders respectively (note that the hydrogen pressure reducing valve thread is reversed, and add the attached O-shaped plastic gasket at the interface, In order to seal), after tightening the nut, close the regulating handle of the pressure reducing valve (that is, loosen), open the high pressure valve of the cylinder, at this time, the high pressure gauge of the pressure reducing valve should be instructed. After closing the high pressure valve, the indicated pressure should not drop. Otherwise, leakage should be eliminated in time (use a gasket or raw material to seal), sometimes the high pressure valve will also leak, pay attention. Then turn the adjustment handle to expel the residual air.
(2) The external gas path connection method introduces the gas in the steel cylinder into the chromatograph, some use stainless steel tubes (? 2 × 0.5mm), and some use pressure-resistant plastic tubes (? 3 × 0.5mm). The use of plastic tubes is easy to operate, so plastic tubes are generally used. If plastic pipes are used, stainless steel liners (? 2 x 20 mm) and some plastics for sealing are required at the joints. The length of the plastic tube from the cylinder to the instrument depends on the need, and it should not be too long. Then use the plastic tube to connect the gas source to the instrument (gas inlet).
(3) The leak detection of the external gas path closes the valve knobs of the carrier gas, hydrogen, and air on the host gas pavement plate, and then opens the high pressure valves of each cylinder, adjusts the output pressure of the low pressure gauge on the pressure reducing valve, so that the carrier gas and air pressure It is 0.35 ~ 0.6Mpa (about 3.5 ~ 6.0kg / cm3), and the hydrogen pressure is 0.2 ~ 0.35 Mpa. Then close the high-pressure valve. At this time, the indicated value of the low-pressure meter on the pressure-reducing valve should not decrease. If it decreases, it indicates that there is a leak in the connecting gas circuit and should be eliminated.
