There is a continuing search for cheaper and quicker analytical procedures. One way to accomplish this is to have an assay whereby two or more analytes can be assayed simultaneously in the same solution.
An example is in U.S. Pat. No. 4,146,602, issued on Mar. 27, 1979, which discloses a simultaneous assay of folate and Vitamin B.sub.12. .sup.57 Co is incorporated in Vitamin B.sub.12 which is rather uncomplicated since Vitamin B.sub.12 is a cobalt containing compound. The problem was how to incorporate .sup.57 Co into noncobalt containing analytes.
The use of chelating agents is well known; however, there is no known use of chelating agents to prepare analytes useful in simultaneous assays.
A paper by Yeh et al., J. Radioanal. Chem., 53, (1979) 327-336 describes the preparation of an assay of indium chelates. A chapter in the American Chemical Society publication Advances In Chemistry Series. No. 198, Modification of Proteins, 369-387, by Meares et al. discusses chelate tagged proteins and polypeptides using cobalt to prepare radiopharmaceuticals.
Egan et al., ".sup.57 Co: A Volume Mark for the TRIPLE-ISOTOPE, Double-Antibody Radioimmune Assay", Immunochemistry. 14 (1977) 611-613 discuss using a chelating agent (ethylenediaminetetraacetic acid) with cobalt, but to prevent adsorption of cobalt to serum proteins.