Abstract: Aqueous solutions of steroid compounds which have biological activity and have a tendency to oxidative degradation at temperatures between 2 and 8° C. on storage in excess of several months are stabilized by the addition of chelators. Aqueous solutions of particular interest are protein containing solutions which mimic the behavior of human bodily fluids such as serum and are therefore suitable as standards for immunoassays for steroids in such bodily fluids. Chelators of particular interest are transition metal chelators especially those which efficiently sequester iron.

Abstract: A method for purifying an aqueous intrinsic factor solution which contains R-protein is disclosed. The method involves adding to the intrinsic factor solution an amount of colloidal silica to disperse lipid emulsion, an amount of cobinamide sufficient to bind substantially all of the R-protein in the solution and an amount of an intrinsic factor affinity resin sufficient to bind the intrinsic factor in the solution, washing the bound cobinamide and the R-protein from the resin, eluting the intrinsic factor from the resin, and dialyzing the eluted intrinsic factor. The purified intrinsic factor possesses less than 0.004 percent cross reactivity with cobinamides, and at least 95 percent of the proteins in the purified material can bind cobalamins. A conjugate of microparticles and the purified intrinsic factor is also disclosed, as is a kit for conducting an assay for cobalamins which includes a conjugate of microparticles and purified intrinsic factor.

Abstract: A method for purifying an aqueous intrinsic factor solution which contains R-protein is disclosed. The method involves adding to the intrinsic factor solution an amount of colloidal silica to disperse lipid emulsion, an amount of cobinamide sufficient to bind substantially all of the R-protein in the solution and an amount of an intrinsic factor affinity resin sufficient to bind the intrinsic factor in the solution, washing the bound cobinamide and the R-protein from the resin, eluting the intrinsic factor from the resin, and dialyzing the eluted intrinsic factor. The purified intrinsic factor possesses less than 0.004 percent cross reactivity with cobinamides, and at least 95 percent of the proteins in the purified material can bind cobalamins. A conjugate of microparticles and the purified intrinsic factor is also disclosed, as is a kit for conducting an assay for cobalamins which includes a conjugate of microparticles and purified intrinsic factor.

Abstract: The current invention is a method, kit and reagents for detecting cobalamins in a sample. The method involves introducing into the sample a first conjugate of a latex or latex-like solid phase linked to affinity purified intrinsic factor with a first linking group at least three angstroms long. The first conjugate and the bound cobalamins in the sample are then exposed to a second conjugate of a cobalamin linked to a detectable enzyme to produce second conjugate bound to first conjugate and unbound second conjugate. The enzyme activity associated either with the solid phase first conjugate or the unbound second conjugate is then detected. By linking affinity purified intrinsic factor to a latex or latex-like solid phase with a first linking group at least three angstroms long, an exzyme assay can be performed which detects levels of cobalamins in patient samples within or below normal ranges found in such samples.