Calibration and mass measurement in negative-ion fast-atom bombardment mass spectrometry

The problem of acceptable accuracy in mass calibration for fast-atom bombardment (FAB) mass spectrometry has recently received some attention (K. Veekey, Rapid Commun. Mass Spectrom., 2, 213 (1988); Idem., Org. Mass Spectrom., 24, 183 (1989). We describe here a calibration method for negative-ionFAB, using gold cluster ions, which provides facile mass calibration over the range from can 200u to 10000u. Under suitable conditions, it is possible to use these ions as internal standards for accurate mass measurement.