  The mass splittings in the pseudoscalar mesons are studied by combining 2+1
flavor domain wall fermion gauge configurations, generated by the RBC/UKQCD
collaborations, and quenched, non-compact, lattice QED configurations. We
extract the QED low energy constants in SU(3) partially quenched chiral
perturbation theory, up to next-to-leading order, and determine the
non-degenerate u, d and s quark masses. Systematic uncertainties due to chiral
extrapolations are discussed. The chiral symmetry breaking of domain wall
fermions on the lattice and its effect in partially quenched chiral
perturbation theory, including QED effects, is also investigated.
