The subject invention provides a sample processing technique for purifying a biological or chemical sample. The invention is particularly well-suited to prepare a sample for mass spectrometry. The process is to be performed in an article having at least one well, in which the surface of the well is at least partially hydrophobic and/or modified with bio-specific ligands. Targeted solutes, such as salts or small molecule contaminants, can be removed from a solution to allow for a purified solution of a desired type of solute, such as peptides and/or proteins.