A standard for the determination of total protein and globulin in biological fluids.

Quantitative estimations of total protein in biological fluids may be performed by the micro Kjeldahl reaction with or without distillation (Rappaport and Lasowski, 1943), by a colorimetric method such as the biuret (Weichselbaum, 1946; Kingsley, 1940), by measuring the specific gravity according to the method of Phillips, Van Slyke, Emerson, Hamilton, and Archibald (1944), by the turbidimetric method (King and Wootton, 1956; Bossak, Rosenberg, and Harris, 1949), or according to the Klett manual. Yeoman (1955) compared the iodometric Kjeldahl and turbidimetric methods using sulphosalicylic acid as reagent and found no significant differences between them, but for small laboratories it is important to use a simple turbidimetric method which is easy to perform. It must be remembered, however, that the turbidimetric methods are dependent on suitable standards. Rappaport and Loew (1957) used in their colorimetric method a peptone solution as a standard for determining proteins in blood plasma. A different standard suitable for turbidimetric determination is proposed for use in quantitative determinations of protein in cerebrospinal fluid, urine, etc. In a similar fashion to Hiss (1904), who used waterdiluted serum as nutrient medium for bacteria, it has been found that human sera diluted 1: 100 in distilled water may be repeatedly autoclaved without coagulation and turbidity and may thus be used as standards. The quantity of protein in a given sample of serum is determined before dilution either by the Kjeldahl method (Benhold, Kylin, and St. Ruszynyak, 1938) or by comparison with a peptone standard. Then this serum of now known protein content is diluted 1: 100, autoclaved, and, if clear, distributed into vials; the vials are sealed and autoclaved again and may be kept indefinitely as standards. Sera containing abnormal globulin are not suitable for this purpose.