The presence of protein and various enzyme activities frequently interferes with the analysis of small molecules in biological samples. Many bioassays require removal of proteins from samples prior to analysis. Among the deproteinization protocols developed over the last half century, perchloric acid (PCA) precipitation has been extensively used in many different sample preparation procedures, since not only does it remove most of the protein present but it also functions to stabilize many of the small molecule analytes. PCA deproteinization methods have been successfully used in the preparation samples prior to quantitation of an array of small molecules, including glycogen, ATP, cAMP, glutathione, antioxidants, etc.The newly designed Depr