Several density purification methods have been proposed to achieve linear scaling in Hartree-Fock and Kohn-Sham calculations. However, only the density is found, while in the traditional diagonalization method the orbitals are also obtained. This could be seen as a drawback as in many cases one would like at least the HOMO and LUMO orbitals and their orbital energies. In this letter, we show how a value for the chemical potential can be obtained as a by-product of density purification methods at negligible cost. Once the chemical potential is known, MO's around the HOMO-LUMO gap can be calculated with the Spectral Transformation Lanczos method. (c) 2006 Elsevier B.V. All rights reserved.