Improved Methodology for Quantitative Determination of Serum and Milk Proteins by Single Radial Immunodiffusion

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Abstract
Single radial immunodiffusion is a simple inexpensive method for quantitating specific proteins in a heterogenous mixture, but it was criticized for its lack of accuracy and repeatability; coefficients of variation of 25% have been reported by some workers. Several refinements were adopted to the single radial immunodiffusion techniques which have appeared in the literature and several new innovations were made. As an integral part of the technique, a computer program was developed that determines the best-fitting curve for a given set of standards, applies this curve to the raw ring-diameters and corrects the data for plate variation and sample dilution. This program reduced errors greatly in calculating protein concentration since all data handling beyond the recording of the precipitant ring diameter is by computer. It also allows for the storage, retrieval and analysis of large volumes of data on many different proteins simultaneously. The overall result of this system was to decrease the coefficients of variation to below 5% for all the milk and serum proteins tested.