Increased Sensitivity in Proton Transfer Reaction Mass Spectrometry by Incorporation of a Radio Frequency Ion Funnel

Abstract

A drift tube capable of simultaneously functioning as an ion funnel is demonstrated in proton transfer reaction mass spectrometry (PTR-MS) for the first time. The ion funnel enables a much higher proportion of ions to exit the drift tube and enter the mass spectrometer than would otherwise be the case. An increase in the detection sensitivity for volatile organic compounds of between one and two orders of magnitude is delivered, as demonstrated using several compounds. Other aspects of analytical performance explored in this study include the effective E/N and dynamic range over which the drift tube is operated. The dual purpose drift tube/ion funnel can be coupled to various types of mass spectrometer to increase the detection sensitivity and may therefore offer considerable benefits in PTR-MS work.3

Measurement of alkyl and multifunctional organic nitrates by proton-transfer-reaction mass spectrometry

“…The PTR-MS is equipped with the newly designed radio frequency (RF) ion funnel which is used to focus ions in the drift tube and hence to increase the detection sensitivity (Barber et al, 2012). This ion funnel uses a series of electrodes with progressively reducing aperture sizes.…”

“…In addition to the standard direct current (DC) electrical field, an alternative current (AC) electric field is provided at a radio frequency that creates a strongly repulsive effective potential near the surface of the electrodes, which combined with the reducing aperture sizes serves to focus the ions radially. This system has been shown to increase the sensitivity by 1 or 2 orders of magnitude (Barber et al, 2012). It is worth noting that operating in the RF mode modifies the dynamic range over which the drift tube is operated and the contribution of the radio frequency to the global effective E/N ratio remains difficult to estimate (Barber et al, 2012).…”

“…This system has been shown to increase the sensitivity by 1 or 2 orders of magnitude (Barber et al, 2012). It is worth noting that operating in the RF mode modifies the dynamic range over which the drift tube is operated and the contribution of the radio frequency to the global effective E/N ratio remains difficult to estimate (Barber et al, 2012).…”

Proton-Transfer-Reaction Time-of-Flight Mass Spectrometry (PTR-TOFMS) for Aroma Compound Detection in Real-Time: Technology, Developments, and Applications

“…An alternative method for improving the sensitivity of PTR-MS instruments involves utilizing a radio frequency, RF, ion funnel within the FDT, which acts to channel reagent and analyte ions into the detection system with greater efficiency (23). Sensitivity improvements for a PTR-TOFMS system equipped with this RF funnel were shown to be one to two orders of magnitude higher than without use of the funnel.…”

Metabolite profiling of Clostridium difficile ribotypes using small molecular weight volatile organic compounds

“…Details of the instrument used in this work and its performance have been described previously (Barber et al 2012;White et al 2013;Wyche et al 2007). PTR-MS exploits proton transfer, in this The C. difficile samples were relatively wet samples grown on solid growth medium.…”