Abstract: The disclosure provides methods and kits for preparing a protein analyte for characterization. The method comprises pretreating a protein analyte in the presence of a magnetic bead in a changing magnetic field; and enzymatically digesting the protein analyte with an endopeptidase enzyme to provide a plurality of peptides for analysis by, for example, LC-MS/MS. The process can be performed in a single tube without the need for desalting or buffer exchange, in less than 2 hours.

Abstract: A method and system for preconcentrating analytes at a microvalve in a microfluidic device is disclosed. The system includes a sample channel loaded with a sample solution. The sample channel includes a semi-permeable membrane microvalve. An electric potential is applied at or across the microvalve to preconcentrate the sample solution when the microvalve is closed. The method includes pretreatments of the device or valve for preconcentration of the analytes. For preconcentration of anionic analytes, the device is baked. For preconcentration of the cationic analytes, the surface of the membrane microvalve is coated with a polycationic coating, and the device is baked.

Abstract: A method and system for preconcentrating analytes at a microvalve in a microfluidic device is disclosed. The system includes a sample channel loaded with a sample solution. The sample channel includes a semi-permeable membrane microvalve. An electric potential is applied at or across the microvalve to preconcentrate the sample solution when the microvalve is closed.