Analytical method development for peptides often proves challenging since these molecules can adsorb to the plastic or glass consumables used in the analysis. This adsorption causes considerable loss and unreliable results, especially in the lower concentration range. Therefore, a variety of antiadsorption strategies have previously been developed to cope with this adsorption, often however incompatible with direct liquid chromatography–mass spectrometry (LC–MS) analysis. Here, a novel antiadsorption diluent is introduced, based on controlled hydrolysis and precipitation of bovine serum albumin. This diluent considerably decreases the adsorption of certain peptides to glass. Moreover, it is LC–MS compatible and can also be used in combination with formic acid and/or acetonitrile addition.