6545XT AdvanceBio LC/Q-TOF

Large molecules like proteins have a large cross-section and can collide with remaining nitrogen in the time-of flight region of the LC/Q-TOF. Even at 1 × 10–7 Torr, collision is not an issue for small molecules. However, for proteins like monoclonal antibodies (mAbs), it leads to a dramatically increased baseline signal. The ultrahigh vacuum of the 6545XT AdvanceBio LC/Q-TOF, achieved by dedicated pumping stages, minimizes these collisions, leading to well-resolved modifications like sugar moiety or lysine loss.

Iterative MS/MS is an acquisition strategy to identify more compounds within a complex sample. It works by performing multiple injections of the same sample. In each subsequent sample acquisition, the precursors selected in all previous runs are excluded. In a single sample run, only the most abundant species get isolated and fragmented; therefore, many interesting features like modifications or impurities will not get identified. With iterative MS/MS, each new injection will move to the next level of lower abundant feature identification.