Calibration in positive and negative ion fast atom bombardment using salt mixtures

Two salt mixtures are described far mass calibration in fast atom bombardment: CsI and NaI for positive ion mode, and CsI and CsF for negative ion mode. The mixtures give many more peaks than CsI and therefore better mass accuracy can be obtained both in scanning and in peak‐matching mode. Their use is especially advantageous for computerized data acquisition. The mass range of 23–3500 for positive ion mode, and 19–3000 for negative ion mode, has been tested and gave good results.