Gas chromatography/electron capture negative-ion mass spectrometry at the zeptomole level.
Anal Chem 1991 Dec; 63(24):2986-2989
An electron capture negative ion mass spectrometer (ECNIMS) was finely tuned to optimize the sensitivity for electrophoric analytes related to DNA adducts and the reference electrophore octafluoronaphthalene (OFN). Each compound gave a strong response by gas spectrometry with electron capture negative ion mass spectrometry. The parameters studied were column head pressure, ion source pressure, ion source temperature, electron energy, and emission current. Higher ion source pressure, adjusted from 1.0 to 2.0 torr with methane, increased the sound/noise (S/N) ratio. It was suggested that the increased S/N with a higher setting for electron energy and the emission current were largely due to the resulting increased population of thermal electrons. When all compounds were tested with settings raised to higher values, the S/N was raised 8.4 to 18.1 fold, with the exception of OFN, which changed slightly. OFN did not respond like the other compounds partially since OFN reacted with oxygen in the column and ion source. In application to a real sample, the new conditions carried the drawbacks of using a higher column head pressure, shortening gas chromatography retention time, and increasing the likelihood of general interferences. Using a conventional head pressure with the other conditions set to high values reduced the response two to three fold. The authors conclude that a tradeoff occurs between sensitivity and resolution.
NIOSH-Publication; NIOSH-Grant; Grants-other; Naphthalenes; Spectrographic-analysis; Chemical-analysis; Chromatographic-analysis; Polycyclic-aromatic-hydrocarbons; Quantitative-analysis; Analytical-methods
Medicinal Chemistry Northeastern University 360 Huntington Avenue Boston, MA 02115
Other Occupational Concerns; Grants-other
Northeastern University, Boston, Massachusetts