Does anyone know what to expect when using a liquid chromatograph?

Gas chromatograph operation and use:

1. Turn on the power switch (or nitrogen cylinder main valve) of nitrogen, hydrogen and air generators, and adjust the output pressure to stabilize around (the gas generator has generally been adjusted at the factory, no need to adjust it).

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2. Turn on the nitrogen switch of the gas purifier of the chromatograph and turn to the "on" position. Note that after observing the pre-column pressure of the chromatograph's carrier gas rise and stabilize for about 5 minutes, turn on the power switch of the chromatograph.

3. Set the temperature of each working part. Condition settings for TVOC analysis: (A) Column box:

The initial temperature of the column box is 50, the initial time is 10 min, the heating rate is 5 min, the termination temperature is 250 min, and the termination time is 10 min. (b) Injector and detector: both 250. Chromatographic conditions during fatty acid analysis:

a) Column box: the initial temperature of the column box is 140, the initial time is 5min, the heating rate is 4 min, the termination temperature is 240, and the termination time is 15min; (b) The injector temperature is 260 and the detector temperature is 280.

Notes:

1. The vacuum test should be carried out in sunny and dry weather, and the surface of the vacuum bubble should be wiped clean. Leaks caused by the surface of the vacuum bubble can seriously affect the actual test results of the vacuum. For the vacuum level test of the same vacuum switch, the interval between each test should not be less than 10 minutes.

Otherwise, the test results will be distorted because the ionized air in the tube cannot return to its normal state in time.

2. It is recommended to test the vacuum degree of the same vacuum switch no more than 3 times a day.

3. When testing the vacuum degree, the leak should be detected first, and then the quantitative test should be carried out after the leak detection is qualified.

4. The red wire clamp is connected to the red wire for the high-voltage line, and the black wire is connected to the black wire for the ordinary line. During the actual wiring process, do not connect the black ordinary cable to the high-voltage output terminal, so as not to cause serious leakage, resulting in test failure or endangering people and equipment.

5. When installing the excitation coil, its positioning indicator line points to the middle seam of the arc extinguishing chamber connection.

6. During the test, the human body cannot contact the high-voltage and magnetic field voltage output terminals, and the tester shell should be grounded.

7. The high-voltage output line and the ion current line should be separated to prevent interference.

8. Cut the magnetic field voltage line and quickly short circuit, otherwise it will seriously damage the instrument and personal safety! Before the experiment, the yellow-green wire must be connected to the electromagnet first, and then to the instrument; At the end of the experiment, pull out the yellow and green test wires on the instrument respectively (do not touch the exposed part of the plug-in with your hands).

9. After the test is completed, the power supply should be turned off, and the high-voltage output terminal should be short-circuited to the ground to avoid being electrocuted by the residual voltage on the charged capacitor.

Analytical method preparation: According to the composition of the sample to be analyzed or the specified method, select the appropriate column type, injection port type, and detector conditions. Determine quantitative methods, such as appearance method, internal standard method, standard addition method.

Prepare the corresponding standard samples, as well as the standards and solvents required for the standard samples. The sample is equipped with the required measuring instruments, syringes, pipettes, and measurement balances.

Chromatographic condition preparation: Prepare the corresponding carrier gas conditions according to the composition of the sample to be analyzed or the specified method. Select the appropriate column model, set the appropriate inlet, column temperature, detector, flow rate, and split ratio.

After the hardware check is correct, turn on the chromatograph and chromatography workstation, and check the parameters, baseline, and status after the instrument is stable until the instrument is ready to enter the sample to be analyzed.

Injection analysis: According to the method and chromatographic conditions, the sample is injected into the injection unit such as the injection port or injection valve using manual and automatic sampler injection methods, and the signal acquisition or chromatography workstation is started at the same time to start recording the retention time. At the same time, the syringe is quickly removed or the injection valve is reset.

Data processing: After the analysis process is completed, the chromatogram or data obtained is manually or used by chromatography workstation for data post-processing. According to the chromatographic peak retention time, the peak identification is qualitative, and the peak area of each component is integrated after the peak start and end points are identified.

Finally, according to the composition, peak area, and calculation method, the peak composition table was obtained, and the whole analysis process was completed.

Power off: Place the gas chromatograph.

The sample inlet, column box, and detector are cooled and shut down, and the air supply flow path and power supply are turned off according to their respective operating regulations.

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When the gas source is supplied with cylinders, each cylinder must be equipped with a gas pressure reducing valve to reduce the high-pressure gas to the required pressure value, and the pressure reducing valve can only use one gas and should not be mixed. Oil-free oxygen pressure reducing valve 0-25MPa - outlet, can be used as a pressure reducing valve other than H2, H2 to use hydrogen special pressure reducing valve (reverse wire!) )

The high-pressure cylinder is usually 40L, and the pressure reducing valve is tightened to the outlet of the high-pressure cylinder with a 300mm live wrench, so that there will be no air leakage. There are two pressure gauges on the pressure reducing valve, one indicates the pressure inside the pressure cylinder and the other indicates the pressure at the outlet of the pressure reducing valve. When the pressure inside the high-pressure cylinder is still 1MPa, it can no longer be used, and it must be refilled.

1. Gas flow regulation.

The basic instrument of this instrument provides gas control systems such as filling column carrier gas, hydrogen, air, auxiliary gas and capillary column gas circuit. See figure VII.

Layout of the air path panel. The control valves of carrier gas, hydrogen, and air on the air circuit panel of the instrument are all closed before leaving the factory.

2. Flow measurement.

When there are special requirements for the instrument's air control system, the gas flow rate can be recalibrated with a soap mist flow meter. The gas path is shown in the connection method diagram (8). Fill the soap film flowmeter with a foaming agent (the preparation of the foaming agent can be prepared with white cat detergent, and the method is the same as that of the leak detection liquid), and connect it to the detector for the required measurement.

In order to reduce the measurement error, a large soap film flowmeter should be used when measuring the gas flow rate of the air path. After the gas is introduced, the time elapsed by the soap film from 0:00 to 10 is measured with a stopwatch, and the gas flow is calculated in ml minutes. In order to avoid contaminating the gas path, it is necessary to pay attention to the use height of the soap liquid inside the flowmeter to prevent the soap film solution from flowing from the flowmeter into the gas path.

3. Installation of filling columns.

Gas chromatograph operation procedure.

1.Turn on the regulated power supply of the gas chromatograph.

2.Turn on the nitrogen valve switch and carrier gas on the purifier. You need to check whether there is any air leakage first, so as to ensure that the machine is airtight.

3.Adjust the total flow to the desired appropriate value, which is measured according to the flow meter.

4.Adjust the flow rate of the diverter valve, the column flow is the total flow minus the flow rate.

5.Open the on/off valves for air and hydrogen and adjust the flow of both to the appropriate value.

6.Set the temperature according to the actual needs of the experiment.

7.Turn on your computer and workstation.

8.When the temperature of the FID detector reaches more than 150 degrees Celsius, the flame of the FID detector is ignited.

9.set the sensitivity and output signal; Once the parameters have been set, the sample can be injected for analysis.

10.At the end of the experiment, it is important to note that the hydrogen and air should be turned off first, and then the column should be purged with nitrogen before shutting off.

1.The sample solution is free of mechanical impurities;

2.Manual sampling: effectively clean the syringe, effectively remove air bubbles, accurately quantify, switch the injection valve quickly, and clean the injection valve with ultrapure water after injection;

3.Automatic sampling: ensure that the sample solution is deep enough (so that the needle tip cannot be buried under the liquid surface); Ensure that the sample solution is free of bubbles, especially if cannula is used; The bottle cap is tight, the solvent of the sample is volatilized if it is too loose, and the bottle gasket may fall off if it is too tight. Unlike bottle pads that are too old, so as not to cause debris to clog the pinhole during needlepricks.

That's about it.