Improved calibration of time-of-flight mass spectra by simplex optimization of electrostatic ion calculations

A novel lime-of-flight mass calibration method has been developed. In contr ast to conventional methods, where the relationship between ion flight time and mass is an arbitrary polynomial equation, this method is based on the physics of ion motion. Parameters needed to describe the physics are numeri cally optimized using a simplex algorithm. Once these parameters are establ ished, unknown masses can be determined from their times-of-flight. This ca libration method gives intrinsically well-behaved results, since nonlineari ties (due to extraction delay, desorption velocity, etc.) are properly take n into account in the time-of-flight calculation. The simplex method is com pared to curve fitting for the analysis of time-of-flight data, and some si gnificant advantages are demonstrated. Salient features of the method inclu de greatly improved mass extrapolation accuracy, no loss of interpolated ca libration accuracy, the ability to obtain an accurate calibration with a mi nimal number of calibrants, and the ability to extract unknown parameters s uch as desorption velocities.