Evaluation of a New DC-Ion Funnel Drift Tube for Use in Proton Transfer Reaction Mass Spectrometry

Abstract

We have developed and characterized a novel drift tube called the direct current-ion funnel (DC-ion funnel) drift tube, consisting of 20 traditional ring electrodes and 5 new DC-focusing electrodes (DC-FEs) for use in proton transfer reaction mass spectrometry (PTR-MS). Ion trajectory simulations demonstrate the ion focusing effect of the DC-FE and DC-ion funnel drift tube. Further comparative experiments show that the PTR-MS with the novel DC-ion funnel drift tube has a higher sensitivity (3.8–7.3 times for the volatile organic compounds considered in this work) than the PTR-MS with a traditional drift tube. Different from conventional radiofrequency (rf) focusing methods, the DC-ion funnel drift tube can realize ion focusing with only a DC electric field and no additional rf power supply, which makes it especially suitable for instruments requiring miniaturization and low power consumption to improve detection sensitivity. In addition, the DC-ion funnel drift tube can easily be coupled to other types of mass spectrometers to increase their detection sensitivity.

Field-Gradient-Focusing Ion Guide for Enhanced Transfer Efficiency of Low-Mass Ions

“…The integration of these ion funnels has favored major gains in sensitivity of MS in alone or coupling ion mobility separation (IMS). − Moreover, the miniaturized ion funnels have also been reported to boost the sensitivity of miniature mass spectrometers (mini-MS). − However, a ion funnel generally suffers from the decreased ion transmission for low-mass ions compared with larger ones, namely, low-mass discrimination effect, which results from the potential barrier along the central axis . To reduce this effect, few approaches have been explored by optimizing either the electrode structure − or electric field. − Recently, a novel focusing quadrupole ion funnel (FQ-IF) was reported to improve the sensitivity of proton transfer reaction mass spectrometry (PTR-MS) . With stacked layers of four-quarter rings and RF application method similar to that of a typical quadrupole, the FQ-IF achieved not only enhanced sensitivity but also decreased low-mass discrimination compared with conventional ion funnels and direct current (DC) drift tubes.…”

Direct detection of acetonitrile at the pptv level with photoinduced associative ionization time-of-flight mass spectrometry

“…The proton transfer reaction mass spectrometer (PTR-MS) is a typical CI-MS that has been widely used to real-time monitor acetonitrile in the atmosphere and exhaled breath. 5,6,[17][18][19][20] Aer a prolonged development, the online detection sensitivity of PTR-MS for acetonitrile has been enhanced to 1070 ± 60 cps ppbv −1 , and the limit of detection (LOD) is as low as 8 pptv. 21 In addition, an atmospheric pressure chemical ionization mass spectrometer (AP-CIMS) has also been employed for atmospheric measurement of trace acetonitrile.…”