Flowing-afterglow mass spectrometry

Over the years many variations of the instrument have been made. In the beginning during the 1960s there was the study of flowing afterglow plasma. This study was done by Eldon Ferguson, Art Schmeltekopf and Fred Fehsenfeld at National Bureau of Standards in Boulder, Colorado. With the flowing afterglow Langmuir probe the electron density within the reaction region of the drift tube can be studied. Since the cost of helium is steady rising some have started to use alternative methods with ambient flowing afterglow to conserve resources. Instead of using continuously flowing afterglow helium some use interrupted helium flow to conserve gas and Schlieren imaging to maximize the molecular ions produced and the instrument step-up. == Application(s) ==

Trace gas analysis One of the first papers reporting the use of the flowing afterglow studied ion-molecule reactions pertinent to the Martian atmosphere. This flowing afterglow technique replaced the then standard stationary afterglow when the movable Langmuir probe was introduced. This problem is circumvented by implementing the selected ion flow tube (SIFT). The flowing afterglow technique can be used to identify and quantify the volatile organic compounds (VOCs) of a sample as long as the fundamental ion chemistry is known. The commonly used ions are H3O+, O2+*, and NO+. All ions have drawbacks and advantages. Strategies that have been employed to identify the VOCs include using gas chromatography coupled with flowing afterglow and using a complement of reagent ions. Also in addition to being able to detect volatile organic compounds, the flowing afterglow technique has also been used to study chronic kidney disease. Studies have been done to create a spectrum of deuterium water and its isotopes to measure total body water, which can be used to determine the water body overload of a patient. That measurement will then be used to determine the stage of renal failure for a patient. ==See also==