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 (Δm) 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. It allows the user to continuously adjust the resolving power and sensitivity to meet current needs. Most importantly, the observed resolving power/sensitivity characteristics are the same at any mass and m/z.