QconCAT (Beynon et al., Nat. Methods, 2005) is an accurate method for absolute quantification of proteins, in which a recombinant chimeric protein (CP) composed of concatenated peptides is used as a stable isotope-labeled internal standard. In this project, we streamline and accelerate QconCAT quantification for biomedical applications. We could quantify proteins in the digests of liquid biopsies (e.g. cerebrospinal fluid) using several overexpressed unpurified QconCAT proteins in parallel without compromising the accuracy, sensitivity and dynamic range.