Quick flush gas for analytical instruments
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In some gas chromatographs, after obtaining the sample gas, only part of it enters the analyzer, and the other part is used for quick flushing (purging). It is also said that the flow rate of the quick flushing (purging) gas is related to the response time. Why is this rapid flushing (purging) gas necessary? It does not pass through the analyzer itself. The analyzer directly uses the incoming sample gas to obtain the analysis results. Why is it related to the flushing gas flow rate? Thanks!
Generally speaking, there are two types of fast purge gases. One is inert purge, which is to blow the original pipeline into inertness in the shortest possible time to avoid interference of irrelevant components on the sample and gain time for sample saving and accurate sampling. The other type uses the sample as a quick blow, which plays the same role as the previous type, that is, an assimilation pipeline to obtain an accurate and representative sample. The choice between the two methods is closely related to the properties of the sample. The poster is talking about this type of quick purge. But in fact, there is also a fast purge gas on analytical instruments, which is used as a safety protective gas.
When the flow rate of the fast flushing gas of some analytical instruments in my installation is low, it will be considered that the instrument is faulty. It is estimated that this quick flushing gas is the third type you mentioned. But how does it protect, and what part of the meter does it purge? If the first two flushing gases are used to assimilate the pipeline, it means that the time to obtain a real sample can be shortened. Because for the same sampling pipeline, the flushing gas flow is large, and the time from the sampling head to the analysis table will be shortened. Can this be understood?