A serum reference standard for automated total protein and album- in procedures.

IN SPITE OF the advocacy, from time to time, of purified serum albumin as a reference standard in protein estimations, many analysts prefer to use pooled sera for this purpose. Such a pool can serve as a reference standard for both total protein and albumin determinations. A difficulty arises, however, with automated procedures; a pool of serum collected in the laboratory usually does not have a sufficiently high total protein and albumin content to permit a check on linearity above the lower region of the normal range. With manual methods it is simple to extend the range of standards upward by increasing the volume of standard solution taken for the test, but with automated procedures it is usually necessary to use standards which themselves cover the required range. Concentration by dialysis of the large volumes of serum required is inconvenient and time consuming. A suitably concentrated, stable standard may be prepared easily from a pooi of unused patient sera by treatment with dried polyacrylamide gel, its use originally suggested by Curtain (1), who found that no measurable loss or denaturation of protein resulted. We used Lyphogel, a commercially available preparation (Gelman Instrument Co., P.O. Box 1448, Ann Arbor, Mich. 48106; Hawksley & Sons Ltd., 12 Peter Road, Lancing, Sussex, U.K.). One liter of the pooled serum is allowed to stand refrigerated overnight with about 5 g of Lyphogel. The concentrated serum is then filtered and distributed among a number of tubes or ampoules and stored at -20#{176}C. Total protein is determined by the Kjeldahl method, and albumin by the same method after fractionation with Na2SO4 (26 g/100 ml). In each case, the protein is precipitated with tungstic acid before digestion. By use of a large pool, occasional variations associated with a few abnormal sera-e.g., possible anomalies in biuret chromogenic power or in salting-out behavior-are apparently swamped (Table 1).