There are many factors to consider when comparing the overall suitability of different quadrupole-based gas analyzers for a given application. These can be categorized into two main areas, inlet/interface suitability and quadrupole mass analyzer suitability. The suitability of the quadrupole mass spectrometer determines very important figures of merit such as precision, stability and detection limit. The quadrupole mass spectrometer includes the ionization method, the transmission characteristics, and the quality of the driving electronics. Unfortunately, these figures of merit are often misrepresented in the commercial literature and it’s this confusion which we seek to address and clarify in this document by making a direct comparison between two different classes of quadrupole analyzers; a typical 6mm rod diameter RGA type instrument typical of many currently on the market, and a higher performance 19mm rod diameter quadrupole analyzer, typical of high end analytical analyzers used in research and industry. We compare these with nominally identical inlet/transfer conditions, so that only the mass spectrometer performance is under consideration. In doing so, we present a direct comparison as it relates the various figures of merit and attempt to remove some of the mystery surrounding confusing analyzer specifications so that potential users of this powerful analytical technique may query manufacturer specifications and therefore make more informed decisions. The specifications that we will discuss are: - Detection Limit (minimum and maximum detectable concentration) - Speed of Analysis (measurement speed and response time) - Analysis Precision (repeatability of measurements) - Analysis Stability (long-term instrument stability) - Dynamic Range (comparison of largest and smallest detectable signals) We will study the above by assessing and comparing the performance of two instruments, the MAX300-CAT and the MAX300-LG. The MAX300-CAT is typical of the high-end RGA based gas analyzers, based upon 6mm quadrupole rod technology, whereas the MAX300-LG is a higher performing analyzer based on 19mm quadrupole rod technology and high-performance electronics.

Practical considerations for quantitative gas analysis with quadrupole mass spectrometers

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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