Comparison of the performance of seven serum deproteinization methods

Abstract

Deproteinization is a method for removing protein components from a sample solution and is used when proteins are an obstacle for evaluating certain substances. Although several deproteinization methods have been reported, their performances have rarely been compared. In this study, we investigated the performance of each deproteinization method and evaluated whether the experimental methods were beneficial for protein detection. Deproteinization was conducted by incorporating equal amounts of one of the following solvents to the serum: ammonium saturated sulfate (AS), acetone, acetonitrile, 10% trichloroacetic acid (TCA), 1N perchloric acid, 10% sulfosalicylic acid, 10% sodium tungstate, and 2/3N sulfuric acid (TGA). Subsequently, five evaluations were conducted: confirmation of serum appearance and turbidity, Lowry method, electrophoresis, high-performance liquid chromatography (HPLC) analysis, and automated clinical chemistry. Serum treated with AS and TGA demonstrated approximately 1/2–1/3 of the protein remaining in the deproteinized samples compared to the original samples. Serum treated with TCA demonstrated excellent protein deproteinization performance, with almost no remaining proteins. The effects of deproteinization on the uric acid, urea nitrogen, and creatinine levels in the samples were minimal. Electrophoresis and HPLC evaluations were found to be superior for evaluating protein concentration in each sample compared to other evaluation methods. It is essential to select a deproteinization method that considers the effect of the treatment on the target substances in the samples.