Is there something between the 5bA and 5aA? Do the squashed TIC graphs tell us anything? Click images for full-size.
Fig 5 summary: A blank, A sample, B blank, B sample, identically scaled
By appearances, the A blank looks clean, the B blank has a minor signal, and both of the Landis samples have a noticable and distinct peak between the 5bA and the 5aA. This does not appear in the graphs of the individual peaks as one of the three ions for the expected 5bA and 5aA, suggesting is is something else that has not been accounted for.
How big is the intervening peak?
(Initial observation by SYI in comments elsewhere).
UPDATE en route: we're told the graphs are better on other pages; we'll update when possible.