The mass calibration standard materials in the low mass region for negative ion chemical ionization (NCI) mode in a magnetic sector mass spectrometer were sought, because perfluorokerosine (PFK) and perfluorotributylamine (PFTBA) used in EI mode scarcely produce negative ions below
m/z 200. The 45 fluorine-containing compounds (5 alkanes, 6 ketones, 5 esters, 5 ethers, and 3 acid anhydrides, etc.) were tested, and the 10 : 1 : 1 mixture of 3 esters [CF
3COOCH
3, C
2F
5COOC
2H
5, C
3F
7COOC
2H
5] and the 1 : 1 : 1 mixture of 3 acid anhydrides [(CF
3CO)
2O, (C
2F
5CO)
2O, (C
3F
7CO)
2O] were found to be advantageous. In their NCI mass spectra, ions were observed at
m/z 69, 85, 113, 128, 144, 178, 194, and
m/z 113, 128, 144, 163, 178, and 194, respectively, with the relative ion intensities of several to 100%. The standard materials for mass calibration and for selected ion monitoring were also purposed.
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