Waters® ProteinWorks™ Auto-eXpress Digest Kits are flexible, broadly applicable sample preparation kits containing pre-measured, lot traceable reagents optimized for the accurate, precise, and robust LC-MS quantification of proteins via the surrogate peptide approach. ProteinWorks Auto-eXpress Low Digest Kit is designed for the digestion of proteins in immuno-purified plasma or serum. ProteinWorks Auto-eXpress High Digest is optimized for the digestion of proteins in whole, non-immuno-purified plasma or serum. To accommodate a wide range of proteins and a variety of diverse surrogate peptides for quantification, either 3-Step (without alkylation and reduction) or 5-Step (with alkylation and reduction) kits are available. In addition to the protocols, care and use information is included.