Gas chromatography failure

Yesterday I aged the column again and noticed that the baseline also fluctuated severely during aging; I suspect this is due to impure carrier gas, gas leaks, or severe contamination of the column.

Is the carrier gas the same bottle? If it’s the same bottle, is the baseline fluctuation in the form of upward and downward zigzags? Check whether the connection between the chromatograph and the workstation is secure, whether the cables are tightly connected, as a loose connection can cause problems!

It is likely caused by a leak; first check for any leaks. If no leaks are found, try replacing the carrier gas.

I agree with what was said above; our department has also encountered the situation you described. It turned out that the connector of the cable linking the chromatograph to the workstation was loose, and replacing that connector fixed the problem……

Reply to 4# zyp0009928: I tried it before and after changing the gas, and the result was the same – the fluctuations were in the form of upward and downward spikes. I also checked the connection between the chromatograph and the workstation, but the baseline still fluctuated severely.

The manufacturer came, replaced the liner, checked the connection between the column and the detector, and also checked for any leaks. None of these measures helped. Later, a small section of the capillary tube that connected the column to the detector was cut off; after aging, the situation improved slightly, but the problem of baseline fluctuations reappeared after about a day. The chromatograph should be fine; it’s not clear what the problem is, as it hasn’t been identified yet. I hope everyone can help; thanks in advance!

Reply to 6# *aoqi198545: I didn’t replace the connectors; I just tightened them, but it didn’t work. It doesn’t seem like the problem lies in this area, as the chromatograph also shows baseline fluctuations, just like on the workstation. If it were simply a poor connection, then one side should work properly while the other wouldn’t.

This post was last edited by zyp0009928 on 2011-7-2 18:45. How many channels do you have? If there are two, try swapping the other one and see; if it works after the swap, it means the original channel is faulty. If there is only one channel, check the connector to see if there is any rusting, especially in the areas where screws are used. A few days ago, one of our channels stopped working. We have 5 chromatographs with 10 channels in total; by replacing that one unused channel with another, the problem was resolved. After you extinguish the fire, check whether the baseline still shows those jagged peaks going up and down; if so, it’s likely that the connection with the corresponding device is poor.

Reply to 9# zyp0009928: After the fire is extinguished, the baseline moves in a straight line.

First, I’d like to thank everyone for their help. I think I’ve figured out what the problem is; I’ll share that with you all here, and then I’ll ask for your assistance again. Our unit uses Shimadzu chromatography equipment; when it was installed in 2008, no gas purification system was put in place. In my opinion, the hydrocarbons and oils present in the carrier gas generated electrical signals at the detector, preventing the instrument from functioning properly – this resulted in an unstable baseline as well as many small spikes in the signal. Next, I need the help of experts to figure out how to solve this problem. An air purification device has been installed today, but the order in which activated carbon, molecular sieve, and color-changing silica gel are placed is incorrect. Still, it should have some effect. Normally, once the purification device is installed, the chromatography results should be normal; the data obtained now are much more reliable than before. However, there are still many small peaks, which suggests that organic impurities have not been completely removed. What do you think of that?