A method for determining a small molecule analyte in a sample suspected of containing the small small molecule analyte and one or more different interfering substances, the method comprising: (a) providing in combination in a medium: (i) the sample, and (ii) two or more different antibody-tracer conjugates wherein the tracer of each different conjugate is the same and wherein the antibody of each different conjugate is different and wherein each different antibody binds to at least two different epitopic sites wherein one of the epitopic sites is a common binding site and one of the epitopic sites is non-common binding site and wherein the non-common epitopic sites are different for each different antibody and wherein each of the non-common epitopic sites is present on a respective interfering substance, wherein the antibody is bound covalently to the tracer and wherein the tracer is a member of a signal producing system, a member of a specific binding pair, or a complex of members of a specific binding pair, (b) incubating the medium under conditions for binding of the different antibodies to the epitopic sites, and (c) examining the medium for the presence and/or amount of complexes comprising the epitopic sites and the antibody-tracer conjugates, the presence and/or amount of the complexes indicating the presence and/or amount of the analyte in the sample, wherein the analyte is mono-epitopic having a molecular weight of about 50 to about 2000 and wherein the common binding site is an epitopic site of the analyte and the non-common binding sites are epitopic sites of interfering substances. (a) providing in combination in a medium: (i) the sample, and (ii) two or more different antibody-tracer conjugates wherein the tracer of each different conjugate is the same and wherein the antibody of each different conjugate is different and wherein each different antibody binds to at least two different epitopic sites wherein one of the epitopic sites is a common binding site and one of the epitopic sites is non-common binding site and wherein the non-common epitopic sites are different for each different antibody and wherein each of the non-common epitopic sites is present on a respective interfering substance, wherein the antibody is bound covalently to the tracer and wherein the tracer is a member of a signal producing system, a member of a specific binding pair, or a complex of members of a specific binding pair, (i) the sample, and (ii) two or more different antibody-tracer conjugates wherein the tracer of each different conjugate is the same and wherein the antibody of each different conjugate is different and wherein each different antibody binds to at least two different epitopic sites wherein one of the epitopic sites is a common binding site and one of the epitopic sites is non-common binding site and wherein the non-common epitopic sites are different for each different antibody and wherein each of the non-common epitopic sites is present on a respective interfering substance, wherein the antibody is bound covalently to the tracer and wherein the tracer is a member of a signal producing system, a member of a specific binding pair, or a complex of members of a specific binding pair, (b) incubating the medium under conditions for binding of the different antibodies to the epitopic sites, and (c) examining the medium for the presence and/or amount of complexes comprising the epitopic sites and the antibody-tracer conjugates, the presence and/or amount of the complexes indicating the presence and/or amount of the analyte in the sample,