Atmospheric and reduced pressure helium microwave-induced plasmas as ion sources for mass spectrometry

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:7201056

Creed, J T

A helium microwave induced plasma is evaluated as an ion source for plasma mass spectrometry. Two different helium plasmas were interfaced. The first was an atmospheric pressure source for the detection of aqueous aerosols. The second was a low pressure source for the detection of gas chromatographic effluents. The distribution of analyte ions as a function of nebulizer flow rate were performed in order to assess the optimum sampling position which would minimize background interferences. Helium microwave induced plasma mass spectrometry provides detection of the halides as positive ions in aqueous samples at the low to sub-ppb levels. Detection limits for metals are in the sub-ppb range. Determination of selenium and bromide isotope ratios are possible down to the low ppb level. Flow injection was used in a preliminary matrix study. A sodium concentration of 2,000 ppm was found to suppress the analyte signals from 15 to 50%. The atmospheric microwave induced plasma was also coupled with a mass spectrometer for the detection of gaseous analytes. The atmospheric pressure source was found to have elevated backgrounds at masses 35 and 37. These elevated backgrounds led to a low pressure torch design. The preliminary analysis of halogenated compounds using the low pressure torch was limited to flow injection of methyl chloride and methyl bromide. This low pressure torch design was modified to facilitate the introduction of gas chromatographic effluents. The linear dynamic range for iodobenzene extends over 3 orders of magnitude starting at 1 picogram. The absolute 3{sigma} detection limit for iodine was 0.1 picogram. A shorter skimmer-to-sampler distance was found to produce superior signal to noise ratios for bromine. This reduced skimmer-to-sampler distance coupled with an aluminum sampling interface provided 0.35 pg detection for bromooctane and bromononane. The detection limit for chlorotoluene was 24 pg.

• Research Organization: Cincinnati Univ., OH (United States)
• OSTI ID: 7201056
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102* -- Chemical & Spectral Procedures
AEROSOLS
AQUEOUS SOLUTIONS
CHARGED PARTICLES
CHEMICAL ANALYSIS
CHROMATOGRAPHY
COLLOIDS
DATA
DISPERSIONS
ELEMENTS
EXPERIMENTAL DATA
FLUIDS
GAS CHROMATOGRAPHY
GASES
HELIUM
INFORMATION
ION SOURCES
IONS
MASS SPECTROSCOPY
METALS
MIXTURES
NONMETALS
NUMERICAL DATA
OPTIMIZATION
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
PLASMA
QUANTITATIVE CHEMICAL ANALYSIS
RARE GASES
SAMPLE PREPARATION
SEPARATION PROCESSES
SOLS
SOLUTIONS
SPECTROSCOPY