PROGRAM CONSIDERATIONS FOR SIMPLEX OPTIMIZATION OF ION LENSES IN ICP-MS

The performance of an inductively coupled plasma mass spectrometer (IC P-MS) is dependent on the ion optic bias potentials, A discussion of t he multielement optimization of the ICP-MS ion optics bias potentials using a Simplex algorithm is presented. Three objective functions were tested: a function developed by Leary; the combined ratio method (CRM ); and the Euclidean distance from multicriteria target vector optimiz ation. Both the Leary and the target vector optimization's performance s were comparable, whereas the CRM optimizations placed an emphasis on obtaining similar signal intensities, Experiments determined that an initial Simplex: starting size of 20% of the parameter space was optim al. A method for the selection of an appropriate target vector by pred icting analyte signal intensity was also investigated. Signal intensit ies for all elements could be predicted with an acceptable margin of e rror (10-30%), provided that the same conditions were used, Comparison s of optimizations using a single mid-mass element vs. multielement op timizations revealed that the multielement approach is only slightly b etter. If the analyst wished to optimize lens settings to favor heavy or light elements, then an average mass was better than a mid-mass opt imization.