Mixed integrable SU(N) vertex model with arbitrary twists

We consider the quantum inverse scattering method for several mixed integrable models based on the rational SU(N)R-matrix with general toroidal boundary conditions. This includes systems whose Hilbert spaces are invariant by the discrete representations of the group SU(2) and the non-compact group SU(1,1) as well as the conjugate representation of the SU(N) symmetry. Introducing certain transformations on the quantum spaces we are able to solve generalized impurity problems including those related to singular matrices.