low concentration gas detection

One definition of “low concentration” would put it at doing work below 1 ppm. Another would consider that any measurements below the usual regulatory values would be deemed “low concentration.” Either way, more care has to be taken in such work. Here are a few tips:

1.     Be very sure of your calibration standard. While technology exists to put sub-ppm concentrations into cylinders, it does not apply to all the gases of interest. It will be necessary to evaluate other approaches, such as permeation devices and on-the-fly gas generators.

2.     Related to this is having a proper zero gas. Bear in mind that zeroing the instrument in air may not be good practice, depending on how contaminated your environment may be with the target analyte. And, as explained in the linked Knowledge Base article, you also have to ensure that your commercial zero gas is sufficiently free of this target analyte.

3.     Does your instrument have sufficient sensitivity to achieve the desired measurement? Ideally, that desired measurement should come in at no lower than 20% of the full-scale range of the instrument. Perhaps your instrument manufacturer can supply a special, more sensitive version of the instrument, that would meet your needs.

In the world of electrochemical sensors, we know that one molecule of the target analyte will produce an electrical current. But, how good are the accompanying electronics? Refer to this KB article on Minimum Detectability.

4.     Be even more wary of interferences. Perhaps, under “normal” circumstances, you can put yourself in a comfort zone of sorts if it takes 20 ppm of an interferent to register a 1 ppm reading of the target analyte. However, if the expected range of your target analyte is 0.2 ppm, then your interferent need only be present at a concentration of 2 ppm to cause a big problem.

Contact us for any help you might need on your low concentration gas detection application.

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