English to French Science Chemistry; Chem Sci/Eng

The HPLC column effluent was split 1 : 10 to reduce the
flow into the mass spectrometer. The electrospray interface was operated in the negative ion mode. The parent to daughter ion transition at 413 to 369 Da was monitored for PFOA and the transition at 415 to 370 Da was monitored for the dual 13C PFOA internal standard.

à la place de 'to' il y a une flèche qui va du 413 au 369 mais je n'arrive pas à l'insérer ici !
que signifie Da à votre avis ? s'agit-il de diffusion ambipolaire ??? merci !