  We investigate hadronic species freeze-out systematics in A+A collisions at
low SPS energies, corresponding to a baryochemical potential above 300 MeV,
analyzing NA49 hadron production data in the framework of the statistical
hadronization model, and in the UrQMD hadronic transport model. Observing no
deviation from universal grand canonical hadro-chemical equilibrium freeze-out,
we argue that the observed hadronic freeze-out points should universally signal
the boundary line of the hadronic phase in the QCD matter phase diagram.
