Large fluctuations in the analysis results of Siemens Chromatography MaxumII – expert explanation
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When chromatography is fed with standard gas, the measured values match the actual values; everything is normal. However, as soon as the sample gas is introduced, the result is twice as large as the actual value, and sometimes the results exhibit significant fluctuations. I’ve spent several days on it; I replaced the sample valve and purged the pipelines, but I still can’t get normal results. It’s frustrating
Does anyone who’s an expert want to analyze this 3-gram amount of oil?
This post was last edited by chengjingbao on 2010-7-16 at 17:26. Check the sampling system to see if the large fluctuations in data are caused by variations in the sample gas. The specific details depend on your configuration and the characteristics of the industry you are in. The most typical example is the measurement of liquid evaporating into gas; this phenomenon occurs when control is not proper.
The flow rate hardly fluctuates; the gas lines have been purged, and the valve numbered 50 has also been replaced. Yet, when using standard gas, the readings are normal, but when using sample gas, the values are twice the actual ones. It’s frustrating……
1. Are you sure your sample gas is normal? Or rather, how do you know that your sample gas value is half of the measured value? 2. Are the sampling pressure and flow rate the same as those used when testing the standard gas?
A stable flow rate only indicates that the sample volume is sufficient; it does not mean that the components of the sample remain constant. How is the representativeness and accuracy of sampling reflected? Under different pressure conditions, there are different flow rate ranges; the same flow rate does not necessarily mean the same pressure! Look for problems mainly in the samples and their preprocessing.
Reply to 6# chengjingbao: After adjusting the parameters, the values are now stable. However, the baseline slope of the sample gas in one of the chromatograms is quite high, while the baseline of the spectrum in the other channel is relatively flat. I can’t figure out why this happens; since all conditions are the same, how can one chromatogram show good results while the other has such a high slope?
Reply to 5# Blue Hedgehog Who Chases the Wind: Based on the historical data we have, the production of the equipment is now controlled by flow meter readings; the current flow rate allows us to estimate the approximate hydrogen content
Reply to 7# syppc: This type of chromatograph also comes in many configurations and is used in various industries； There are two things you need to do; one is related to the characteristics of the industry, which involves identifying problems ； One related to the instrument, for finding problems. For those with a high slope, check for any other phenomena. Since there is some hands-on skill available, examine another type of detector; if possible, clean it as well.
Do you already know the true value of the sample gas? Do you still need to take the test?
Reply to 9# chengjingbao: It’s now basically certain that it’s related to the chromatography column; we’re preparing to replace it