Due to the complicated structure, many conditions, and long recovery preparation time, gas chromatographs often have various abnormalities during use. Failure to maintain for the cause can have serious consequences. The following is an introduction to the abnormal conditions and maintenance of the gas chromatograph in the application.
The gas chromatograph did not change the detection signal after the injection, the instrument did not show a peak, and the output was still straight. In this case, check one by one from the sample syringe, the inlet to the detector.
1. First check if the syringe is clogged. If there is no problem,
2. Check that the graphite gasket of the inlet and detector is tight and airtight.
3. Then check the column for leaks and leaks.
4. Finally, observe whether the detector exit is unblocked.
5, the smooth exit of the detector is very important, some people will encounter such problems in the work: the previous day the instrument work is still normal, the next day after the start, there is no response peak signal. Check that the inlet, syringe, gasket and column are all normal, but there is no peak. Unintentionally, the inlet pressure of the inlet is not up to the set value, and it is always high. It is suspected that the ECD tester exit is not Unblocked. Since the emissions of ECD have a certain amount of radioactivity, the ECD outlet is led to the outside. At that time, it was the turn of autumn and winter. After the rainwater entered the E CD discharge port, it was frozen. As a result, the outlet of the instrument E CD was blocked, the column head was kept high, the gas could not flow in the gas path, and the sample could not be loaded to the detector. So there is no peak.
Second, the baseline problem:Gas chromatographic baseline fluctuations and drifts are baseline problems, and baseline problems can increase measurement errors and sometimes even cause the instrument to fail to function properly.
1. When encountering baseline problems, first check whether the instrument conditions have changed, and whether new gas cylinders and equipment accessories are newly replaced.
2. If there are changes or conditions change, it is necessary to check whether the baseline problem is caused by these changes. Generally, this change is often the cause of the baseline problem. Some people have encountered this situation at work: the new carrier gas is not pure enough, and after changing the overload gas, the baseline gradually rises (the baseline is not immediately changed due to the carrier gas purification tube). After the next day, the baseline was very high with strong baseline jitter and all peaks were noisy and could not be detected. After inspection, the problem occurred on the newly exchanged carrier gas, and immediately after the replacement of the carrier gas, it returned to normal.
3. When the above reasons that may cause the baseline problem are excluded, the injection pad should be inspected for aging (it should be a good habit of regularly changing the injection pad);
4. Whether quartz wool should be replaced;
5. Is the liner clean? It is worth mentioning that when cleaning the liner, it can be fully soaked with the solvent of the final volume of the test, then ultrasonically cleaned for a few minutes, then placed in a high temperature furnace to a temperature slightly higher than the working temperature, and then re-installed.
6. In addition, detector contamination can also cause baseline problems, which can be solved by cleaning or hot cleaning.
Third, the failure caused by peak loss:There are two reasons for the loss of peaks: one is pollution in the gas path, and the other may be that the peaks are not separated.
(1) The first case can be solved by multiple air runs and cleaning air paths (inlet, detector, etc.).
1. In order to reduce the pollution to the gas path, the following measures can be taken: there should be a high temperature cleaning process in the final stage of temperature programming;
2. The sample injected into the inlet should be clean;
3. Reduce the use of high boiling oils;
4. Use as high an inlet temperature, column temperature, and detector temperature as possible.
(2) The second case of peak loss is that the peaks are not separated. In addition to the above reasons, it may also be caused by a decrease in column efficiency caused by system pollution, or due to aging of the column, but the peak caused by the aging of the column. Loss is gradual and slow.
False peaks are generally caused by system contamination and air leaks, and their solutions are also addressed by checking for leaks and removing contamination. The normal baseline should be recorded during normal work for reference during maintenance.
Here is only the j maintenance method for three common problems in the work. The gas chromatograph has more fault points and longer fault recovery time. Therefore, the key to equipment maintenance is the correct analysis of the cause. Every time you inspect a component, you must compare the results of the analysis before and after, so as not to enlarge the problem. I believe that through repeated trials, the problem will be solved successfully.
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