Importance of enhanced mass resolution in removing interferences when measuring volatile organic compounds in human blood by using purge-and-trap gas chromatography/mass spectrometry.
The number of volatile organic compounds (VOCs) that can be purged from human blood is so great that they cannot be separated completely by capillary gas chromatography. As a result, the single-mass chromatograms used for quantitating the target compounds by mass spectrometry have many interferences at nominal (integer) mass resolution of a quadrupole mass spectrometer. The results of these interferences range from small errors in quantitation to completely erroneous results for the target VOCs. By using a magnetic sector mass spectrometer, these interferences at nominal mass can be removed at higher resolution by lowering the ion chromatogram windows around the masses of interest. At 3000 resolution (10% valley definition), unique single-ion chromatograms can be made for the quantitation ions of the target VOCs. Full-scan mass data are required to allow the identification of unknown compounds purged from the blood. By using isotope-dilution mass spectrometry, most target VOCs can be detected in the low parts per trillion range for a 10-mL quantity of blood from which the VOCs have been removed by a purge-and-trap method.
Division of Environmental Health Laboratory Sciences, National Center for Environmental Health and Injury Control, Centers for Disease Control, Public Health Service, U.S. Department of Health and Human Services, F 17, 1600 Clifton Road, 30333, Atlanta, Georgia, USA.
M A
MA
Bonin
D L
DL
Ashley
F L
FL
Cardinali
J M
JM
McGraw
D G
DG
Patterson