Surfactants are often used to solubilize cell membrane and/or to prevent peptide/protein to be adsorbed on the container surface. However, the presence of surfactant may deteriorate LC column and LC/MS system, results in poor repeatability. By using MSpak GF-4A, surfactant can be removed prior to sample being introduced to the analytical column. Therefore provides good repeatable analysis and reduces the time required for sample preparation. The following examples of surfactants can be removed by GF-4A.