Experimental Validation of the Digital Tandem Mass Filter.

This work presents the experimental evaluation of a digital tandem mass filter that is composed of two digitally operated low-resolution mass filters in series whose mass windows are shifted with respect to each other. The overlap of the mass windows allows the resolution (Δ) of ions to be narrowed to provide better resolving power, while the acceptance of the tandem mass filter is defined by the acceptance of the first low-resolution quadrupole. Our experiments show that digital operation fulfills the promise of the tandem mass filter for providing better ion transmission at the same or better resolving power as a single quadrupole mass filter.

Peak structure with a quadrupole mass filter operated in the first stability region.

Rationale: In the development of commercial quadrupole mass spectrometers, there is an interest in understanding the factors that affect the transmission and peak shape of ions passing through the mass filter. These include the ion collection effects of the ion optics that lead to the presence of a peak structure.

Methods: The peak structure can be observed by increasing the ion's axial kinetic energy and reducing the mass step size in a mass spectrum.

Reducing ion reflections at the quadrupole pre-filter/mass filter boundary: Simulation and experiment.

Rationale: Ion reflections at the quadrupole pre-filter/mass filter boundary lead to the trapping of ions within the pre-filter. The trapped ions lead to space charge effects on the transmission of ions through this region which become more of an issue with the development of high sensitivity mass spectrometers which have bright ions beams.

Methods: Simulations were carried out matching the effective potentials at the pre-filter/mass filter boundary to reduce the field gradients across the boundary by reducing the field radius of the pre-filter.

Quadrupole pre-filter/mass filter transmission profiles: Experiment and simulation.

Rationale: Quadrupole pre-filter transmission profiles are shown to be affected by the presence of trapped ions within the pre-filter of a quadrupole mass spectrometer. Trapped ions are the result of ions reflected at the pre-filter/mass filter boundary and lead to space charge effects that can affect the shape of the pre-filter transmission profile, ion beam stability, peak width and peak intensity. The development of high sensitivity mass spectrometers with bright ion beams leads to greater numbers of trapped ions.

Genome Sequences of Beak and Feather Disease Virus in Urban Rainbow Lorikeets (Trichoglossus haematodus).

Beak and feather disease viral genomes were recovered from two deceased juvenile urban rainbow lorikeets (Trichoglossus haematodus) that lacked tail feathers. These genomes share ~95% pairwise identity with two beak and feather disease virus (BFDV) genomes identified in wild and captive Australian T. haematodus birds and ~92% identity to those in wild New Caledonian T.