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The Application of the Falling Drop Technic

The Quantitative Determination of Pneumococcal Polysaccharide

From the Hygienic Laboratory, University of Michigan

Abstract

A method has been presented for the quantitative analysis of pneumococcal polysaccharide based on the falling drop time of NaOH solutions of antigen-antibody precipitates. Falling drop time data were converted to density difference values by calculation. When the density difference of precipitates formed by the interaction of known quantities of polysaccharide with an antiserum was plotted as the ordinate and milligrams of polysaccharide as the abscissa, a standard curve was obtained. For the estimation of unknown quantities of polysaccharide, the density difference was found. The amount of polysaccharide was found by projection on the standard curve.

The results indicate that the method just presented is simple, rapid and accurate. The average variation in the amount of polysaccharide determined by this technic when compared to the amount actually present was 7 per cent for a total of 145 determinations.

Footnotes

¹ This is a portion of the work submitted in partial fulfillment of the degree of Doctor of Philosophy at the University of Michigan.

² Present address: The Public Health Research Institute of The City of New York, Inc.