An affinity matrix for use in affinity based molecular pull down and immunoprecipitation procedures. The affinity matrix comprises a polymeric support, a dye attached to a fraction of the polymeric support to enable optical detection of the polymeric support, and an affinity ligand other than the dye attached to a fraction of the polymeric support for the capture of a molecule. Also provided is a method for the isolation of a biomolecule from an aqueous solution. The method comprises combining the aqueous solution with an affinity matrix comprising a polymeric support and separating the affinity matrix from the aqueous solution. A dye is attached to a fraction of the polymeric support which enables optical detection and monitoring of the affinity matrix and, accordingly, reduces the likelihood of the loss of affinity matrix during the separation step. In addition, an affinity ligand other than the dye is also attached to a fraction of the polymeric support for the capture of the biomolecule.