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 m ) 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 .