Shanghai Baidian Gas Chromatograph Abnormal Maintenance Skills
Due to the complex structure, multiple condition settings, and long recovery preparation time, gas chromatographs often have various abnormalities during use. If you do not maintain for the cause, it will cause serious consequences. The following is an introduction to the abnormal conditions that are likely to occur in the application of gas chromatographs and their maintenance. Shuttle Racking System,Radio Shuttle System,Radio Shuttle Racking System,Four Way Shuttle System Changchun Rochiev Intelligent Equipment Manufacturing Co., Ltd. , https://www.rochiev-en.com
No peaks after injection
After the sample is injected, the gas chromatograph detects that the signal has not changed, the instrument does not produce a peak, and the output is still a straight line. When encountering such a situation, it should be checked one by one in the order from sample injector, sample inlet to detector. First check whether the syringe is blocked. If there is no problem, then check whether the graphite gasket of the inlet and the detector is tight and leak-free, then check the column for cracks and leaks, and finally observe whether the detector outlet is smooth. The smoothness of the detector outlet is very important. Some people will encounter such problems in their work: the instrument was working normally the previous day, but there was no response to the peak signal after the next day's startup. Check the inlet, syringe, gasket
Both the column and the column are normal, but there is no peak. I accidentally found that the inlet column pressure did not reach the set value, and it was always too high. At this time, I suspected that the outlet of the ECD detector was not smooth. Because ECD emissions are radioactive, ECD outlets are led outdoors. At the turn of autumn and winter, the rainwater froze after entering the ECD outlet, so the outlet of the instrument ECD was blocked, the column head pressure remained high, the gas could not flow in the gas path, and the sample could not be loaded to the detector, so it was Peak out.
In this case, as long as the ECD discharge pipe is soaked in hot water, the problem can be solved after the ice melts.
Baseline problem
Gas chromatographic baseline fluctuations and drifts are both baseline issues. Baseline issues can increase measurement errors and sometimes even cause the instrument not to work properly. When encountering baseline problems, you should first check whether the instrument conditions have changed, and whether there are new gas exchange cylinders and equipment accessories in the near future. If there is a replacement or a change in conditions, you should first check whether the baseline problem is caused by these changes. Generally speaking, this change is often the cause of the baseline problem. Some people have encountered this situation at work: the purity of the new carrier gas is not enough. After the overload gas is replaced, the baseline gradually increases (due to the carrier gas purification tube, the baseline does not change immediately). After starting up the next day, the baseline was very high, with strong baseline jitter. All peaks were obscured by the noise and could not be detected. After inspection, the problem occurred with the newly changed carrier gas. After the carrier gas was replaced again, it returned to normal immediately.
When the above causes of the baseline problem are eliminated, you should check whether the sample pad is aging (a good habit of replacing the sample pad regularly); whether quartz wool should be replaced; whether the liner is clean. It is worth mentioning that when cleaning the liner, you can first fully soak it with the solvent of the final volume of the test, then clean it with ultrasonic waves for a few minutes, then put it in a high temperature furnace and heat it to a temperature slightly higher than the working temperature, and then reinstall it. In addition, contamination of the detector may also cause baseline problems, which can be solved by cleaning or thermal cleaning.
Peak loss, false peak
There are two reasons for the loss of peaks. One is the contamination in the gas path, and the other is that the peaks are not separated. The first situation can be solved by multiple air runs and cleaning the gas path (inlet, detector, etc.). In order to reduce the pollution to the gas path, the following measures can be adopted: a high-temperature cleaning process should be performed in the final stage of the program temperature rise; the sample injected into the inlet should be clean; the use of high-boiling oils should be reduced; Sample port temperature, column temperature and detector temperature. 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 the decrease in column efficiency due to system contamination, or due to column aging, but the peak loss caused by column aging is gradual ,slowly.
The false peak is generally caused by system pollution and air leakage, and its solution is also solved by checking the air leakage and removing the pollution. The normal baseline should be recorded in normal work, so as to make reference during maintenance.
Here are only the maintenance methods of three common problems in the work. There are many failure points of the gas chromatograph, and the failure recovery time is also long. Therefore, the key to equipment maintenance is correct analysis of the cause. Every time a component is checked, the results of the analysis before and after should be compared, so that the problem is not enlarged. I believe that through repeated attempts, the problem will be successfully solved.