  In this work, using maximal elements in generalized Weierstrass semigroups
and its relationship with pure gaps, we extend the results in \cite{CMT2024}
and provide a way to completely determine the set of pure gaps at several
rational places in an arbitrary function field $F$ over a finite field and its
cardinality. As an example, we determine the cardinality and a simple explicit
description of the set of pure gaps at several rational places distinct to the
infinity place on Kummer extensions, which is a different characterization from
that presented by Hu and Yang in \cite{HY2018}. Furthermore, we present some
applications in coding theory and AG codes with good parameters.
