Abstract: An improved method of separating free from bound fractions in a solid phase column immunoassay procedure of the type wherein a solution is contacted with a composite comprising an activated polysaccharide matrix covalently coupled to a primary antibody, wherein the improvements comprise:(a) coupling an .alpha.,.omega.-diaminospacer to said activated polysaccharide matrix via one of said .alpha.,.omega.-diamino-spacer's amino groups thereby forming a derivatized polysaccharide matrix; and(b) covalently coupling said derivatized polysaccharide matrix to an antibody selected from a group consisting of primary and secondary antibodies via a bifunctional coupling agent having a formula ##STR1## WHEREIN N IS AN INTEGER FROM 1 AND 6 AND WHEREIN E IS AN INTEGER FROM 1 TO 2.

Abstract: A method of separating free from bound fractions in an immunoassay procedure of the type wherein a solution is contacted with a composite comprising a derivatized polysaccharide matrix covalently coupled to an antibody by a bifunctional coupling agent, wherein the improvement comprises selecting said bifunctional coupling agent from a group comprising ##STR1## WHEREIN N IS AN INTEGER FROM 1 TO 6 AND WHEREIN E IS AN INTEGER FROM 1 TO 2.

Abstract: A method of separating free from bound fractions in an immunoassay procedure of the type wherein a solution is contacted with a composite comprising a finely divided, activated, polysaccharide matrix covalently coupled to a primary antibody, wherein the improvements comprise:(a) coupling an .alpha.,.omega.-diaminospacer to said finely divided, activated, polysaccharide matrix via one of said .alpha.,.omega.-diaminospacers's amino groups thereby forming a finely divided, derivatized, polysaccharide matrix;(b) covalently coupling said finely divided, derivatized, polysaccharide matrix to an antibody selected from a group consisting of primary and secondary antibodies via a bifunctional coupling agent having a formula ##STR1## WHEREIN N IS AN INTEGER FROM 1 AND 6 AND WHEREIN E IS AN INTEGER FROM 1 TO 2; AND(c) using a polysaccharide matrix having an average wet maximum dimension of 1 to 18 .mu..

Abstract: Derivatives of steroids containing an imidazole group specifically bind to the desired antibody without nonspecifically binding to other substances (e.g., proteins in a patient's plasma or serum and the surfaces of reaction vessels).

Abstract: The derivatives of digoxin useful in the radioimmunoassay of digoxin having the following formulae: ##STR1## where R is a carboxylic acid ester. These derivatives are formed by the following process: (1) reacting the carboxylic acid in the presence of trifluoroacetic anhydride with a solution of digoxin in an inert, nonaqueous solvent medium, (2) adding water so as to form the above derivatives, (3) purifying the above derivatives from other constituents of the reaction mixture and (4) radio-labeling these derivatives for use as a labeled hapten in the radioimmunoassay of digoxin.The preferred carboxylic acids are imidazoleacetic acid and p-hydroxyphenylpropionic acid. The preferred radioactive isotope is .sup.125 I.