DOES THE OBSERVED MASS IN QUADRUPOLE MASS FILTERS OPERATED UNDER STANDARD ANALYTICAL CONDITIONS DEPEND ON ISOMERIC ION STRUCTURE

Recently published results have reported that mass displacements, whic h could reach 0.34 u, were observed in a quadrupole mass filter. An in teraction between the dipole moment of ions and the quadrupolar RF fie ld was then proposed to explain these mass displacements. We were inte rested by such an access to ion structure and decided to reproduce the se results. Two sets of experiments were performed using two single-st age quadrupole mass spectrometers operated under standard analytical c onditions. Studies of the influence of resolution, source pressure and presence of helium or polar gas in the quadrupole enclosure on potent ial mass displacement detection have been performed. Nevertheless, we never observed significant mass shifts.