Previous quantitative analyses of ion sputtered brass alloy surfaces have indicated preferential sputtering of the zinc with a possible effect of crystalline structure in going from the pure face-centered-cubic alpha phase to the mixed alpha plus body-centered-cubic beta phase. The application of principal component analysis-target factor analysis allows the use of the more surface sensitive MW Auger transitions despite the complete overlap of the MW peaks from copper and zinc. Quantitative analysis of these signals confirms the occurrence of preferential sputtering, including the phase dependence. Specifically, the zinc/copper concentration ratio from the surface vs the bulk shows a discontinuity as the bulk composition changes from the alpha to the alpha+beta phase.