The DM formalism originally developed for the calculation of electron impact ionization cross-sections of neutral targets and positive ions, is extended here to negative atomic ions. We use a fitting procedure based on the (few) available experimental data for H-, B-, C-, and F-to determine the set of additional empirical parameters required for the application of the DM formalism for negative ion targets. Subsequently, those parameters were used to calculate the O- detachment cross-section, for which two sets of experimental data are available for comparison and the Li- detachment cross-section, for which no experimental data are available. (C) 2003 Elsevier B.V. All rights reserved.