A method for the determination of free neuraminic acid split from red blood cell receptors by attached Newcastle disease virus during simultaneous elution and hemolysis.

Determination of free neuraminic acid in chicken red blood cell (RBC) hemolysate becomes possible after deproteinization of the hemolysate by ethanol-chloroform followed by removal of the solvents by evaporation. This procedure permits the determination of in situ neuraminidase activity of virions preadsorbed on RBC receptors when the virus elution and hemolysis proceed simultaneously.