In some embodiments, a quantitative analysis of at least one ion signal associated with a sample, which is detected by a mass spectrometer having at least two tandem quadrupole instruments, is employed to select one of the following operational modes for further mass analysis of the sample: (a) utilizing both quadrupole instruments as mass resolving filters, and (b) utilizing one quadrupole instrument as a mass resolving filter and utilizing the other as a linear ion trap. In some embodiments, the quantitative analysis of the ion signal comprises comparing the ion signal intensity with a predefined threshold.