OPERATION OF A QUADRUPOLE ION-TRAP FOR PARTICLE BEAM LC MS ANALYSES/

Several operational modes of the quadrupole ion trap mass spectrometer (QITMS) were investigated to perform particle beam (PB) LC/MS analyse s. The PB interface was directly coupled to a QITMS without the use of an external ion source; vaporization of the particle beam and ionizat ion by electron ionization (EI) were accomplished within the ion trap. Ions from residual LC solvent initially caused space charging and a s ignificant extent of chemical ionization (CI), which degraded the qual ity of EI mass spectra. Ejection of solvent ions prior to mass analysi s minimized both space charging and CI, which allowed acquisition of E I spectra that compared favorably to EI spectra obtained from pure sam ples vaporized off of a solids probe and to library EI spectra. Isocra tic LC/PB/QITMS analyses for several pesticides show lower limits of d etection (LODs) than those reported for LC/PB/MS analyses on PB system s using quadrupole mass analyzers. Typically nonlinear calibration cur ves are produced, although linear calibrations have been observed for some analytes.