A method for deproteinization of blood and other body fluids.

Deproteinization is a necessary step in many procedures for the chemical analysis of body fluids. A variety of reagents have been used for this purpose, especially in blood analysis. Of these perhaps tungstic acid and trichloracetic acid are the most widely used to-day, and for this reason we may consider them a moment. Folin and Wu (1919) introduced tungstic acid to prepare proteinfree filtrates for their system of blood analysis. In this method it is usual to employ 667 m.Eq. of the acid to precipitate the proteins from a litre of plasma or whole blood and twice this concentration to deproteinize the same volume of packed erythrocytes. With the use of sodium tungstate and sulphuric acid equivalent amounts of Na and SO4 are of course added to the filtrate. Trichloroacetic acid is commonly used in a 5% (w/v) concentration in the filtrate, and it must be used in not less than half of this concentration. If the blood is diluted 1 in 10 this means that the acid used equals 4 m.Eq./litre blood and the filtrate is more than 3.0 N acid. For such reasons tungstic and trichloroacetic acids are unsuitable deproteinizing agents in many analytical methods, in procedures for the isolation of solutions for chromatography, and other modern techniques. It therefore seems desirable to have other means of deproteinization that will avoid the addition of gross amounts of extraneous matter to the filtrates, that can be rapidly applied, yield filtrates near neutrality, and cause a minimum distortion of the chemical picture of the fluids concerned. The present communication is an attempt in this direction. A method is described for the preparation of protein-free filtrates of blood, which is also applicable to other body fluids. It depends on the adjustment of the pH of the diluted fluid in question to a value suitable for the precipitation by heat of the proteins present. Plasma, cells, and whole blood require about 50, 27, and 40 m.Eq. acetic acid/l. respectively for pH adjustment. The filtrates obtained after heating briefly at 1000 C. are clear and colourless and remain clear on addition of sulphosalicylic acid.