1. A method for optimizing accuracy and precision of measured mass-to-charge ratio (m/z) values obtained in a combined separation—mass spectrometry measurement, characterized by the step of: calculating corrected m/z values using a preselected instrument-specific calibration function containing at least one measured quantity and at least one optimized calibration coefficient value, said optimized calibration coefficient is determined by selectively adjusting values of calibration coefficients of said preselected instrument-specific calibration function until a preselected peak of a mass accuracy histogram is positioned at a mass residual value of zero and a minimized peak width is obtained.