Photoionization in air with ion mobility spectrometry using a hydrogen discharge lamp
An ion mobility spectrometer (IMS) suitable for operation in air at atmospheric pressure using direct gaseous photoionization (PI) was demonstrated by using an on-axis mounted 10.2-eV hydrogen discharge lamp (lambda/sub max/ 121.5 nm). Penetration of UV photons into air in PI-IMS was determined by using product ion intensity and analyte location as 15 mm from the lamp window. Spectra were obtained for ten organic compounds and were simple with one to three peaks. Detection limits in PI-IMS ranged from 0.1 to 50 ppb directly without any sample preconcentration and working ranges were 1000-10,000. Detection limits were similar to those for conventional chemical ionization but working ranges were improved 100- to 1000-fold. Operation of PI-IMS in nitrogen with on-axis placement of the discharge lamp was complicated by penetration of photons > 2 cm through the Bradbury-Nielson shutter leading to analyte ionization in the drift region. Use of nitrogen as a drift gas was possible with the lamp placed perpendicular to gas flow. However, sensitivity and limits of detection were better with the on-axis design in air since ionization volumes were 7.1 cm/sup 3/ for the on-axis mount but only 4.0 cm/sup 3/ for the side-mount.
- Research Organization:
- New Mexico State Univ., Las Cruces
- OSTI ID:
- 5346977
- Journal Information:
- Anal. Chem.; (United States), Vol. 58:11
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
54 ENVIRONMENTAL SCIENCES
AIR
QUALITATIVE CHEMICAL ANALYSIS
AIR POLLUTION MONITORS
PERFORMANCE
SPECTROMETERS
ATMOSPHERIC PRESSURE
EXPERIMENTAL DATA
GAS DISCHARGE TUBES
GASEOUS WASTES
HAZARDOUS MATERIALS
HYDROGEN
ION MOBILITY
ORGANIC COMPOUNDS
PHOTOIONIZATION
CHEMICAL ANALYSIS
DATA
ELECTRON TUBES
ELEMENTS
FLUIDS
GASES
INFORMATION
IONIZATION
MATERIALS
MEASURING INSTRUMENTS
MOBILITY
MONITORS
NONMETALS
NUMERICAL DATA
PARTICLE MOBILITY
WASTES
400104* - Spectral Procedures- (-1987)
500200 - Environment
Atmospheric- Chemicals Monitoring & Transport- (-1989)