A Simple Visual Turbidimetric Estimation of Serum Gamma Globulin
B. Levin, Victor G. Oberholzer, T. P. Whitehead · Journal of Clinical Pathology · 1950
It was shown in our paper (page 260) comparing electrophoresis and precipitation methods that the y-globulin fraction of serum could be determined by precipitation with a saline ammonium sulphate reagent giving results which were in good agreement with those obtained by electrophoresis.It was noticed in these precipitations that the turbidity produced by the addition of the reagent appeared to be directly proportional to the amount of y-globulin, as determined by subsequent micro-Kjeldahl analysis.Since this might provide a simple method of estimating this fraction, it was decided to investigate further the correlation between serum y-globulin and the turbidity produced.Method Serum, 0.1 ml., is added to 4.9 ml. of saline ammonium sulphate solution (prepared by dissolving 193 g.A.R. ammonium sulphate and 40 g.sodium chloride in distilled water and making up to 1 litre) in a test tube, which is inverted several times to mix, and allowed to stand for 15 minutes to develop maximum turbidity.The turbidity is then read visually against the turbidity standards of Kingsbury, as in the thymol turbidity test, the units of turbidity being calculated in the same way.Where the turbidity is high, the mixture is diluted by adding a further 5, 10, or 15 ml. of reagent and the reading obtained multiplied by the corresponding dilution factor.These proportions are slightly different from those used in the chemical estimation since, if the latter are used, the turbidity produced is outside the range of the standards.Alternatively a fresh volume of 0.1 ml. of serum may be added to 9.9 ml., 14.9 ml.. or 19.9 ml. of reagent, and the reading obtained multiplied by the appropriate dilution factor.