Murine and rat monoclonal antibodies (MAbs) were purified to 90-95% homogeneity from ascites in a single step using an ABx liquid chromatography column which utilizes a silica-based mixed-mode ion-exchange matrix. The resulting MAbs were highly immunoreactive reflecting the mild conditions used for this procedure. The column was also useful for detecting and separating multiple immunoglobulins present in the same ascites. For one ascites sample, three immunoglobulin species, which apparently differed only in their light chains, were resolved using this column and differed greatly in their immunoreactivity.