A conjugate having a formula (hapten) m -(linker) n -(reactive group) o -(carrier) p where: the hapten is a quinoxaline; the linker, for coupling a hapten to a reactive group, is a polymer comprising from 1 to 15 ethylene glycol units; the reactive group, for coupling a linker to a carrier, is selected from the group consisting of an amine-reactive group selected from the group consisting of an isothiocyanate, an isocyanate, an acyl azide, an NHS ester, an acid chloride, an aldehyde, a glyoxal, an epoxide, an oxirane, a carbonate, an arylating agent, an imidoester, a carbodiimide, an anhydride, and combinations thereof; a thiol-reactive functional group selected from the group consisting of a haloacetyl, an alkyl halide, a maleimide, an aziridine, an acryloyl derivative, an arylating agent; a thiol-disulfide exchange reagent selected form the group consisting of a pyridyl disulfide, a TNB-thiol, a disulfide reductant, and combinations thereof; a carboxylate reactive functional groups selected from the group consisting of a diazoalkane, a diazoacetyl compound, a carbonyldiimidazole compound, and a carbodiimide; a hydroxyl-reactive functional groups selected from the group consisting of an epoxide, an oxirane, a carbonyldiimidazole, a N,N'-disuccinimidyl carbonate, a N-hydroxysuccinimidyl chloroformate, a periodate oxidizing compound, an alkyl halogen, and an isocyanate; an aldehyde and ketone reactive functional groups selected from the group consisting of a hydrazine, a Schiff base, a reductive amination product, a Mannich condensation product, and combinations thereof; an active hydrogen-reactive compound selected from the group consisting of a diazonium derivative, a Mannich condensation product, an iodination reaction product, and combinations thereof; a photoreactive chemical functional group selected from the group consisting of an aryl azide, a halogenated aryl azide, a benzophonone, a diazo compound, a diazirine derivative, and combinations thereof; the carrier is selected from the group consisting of an amino acid, a polypeptide, a protein, a nucleoside, a nucleotide, a nucleotide chain, a nucleic acid, DNA, RNA, mRNA, a polymer, aminoalkyl agarose, aminopropyl glass and crosslinked dextran; m, n, o and p are 1. the hapten is a quinoxaline; the linker, for coupling a hapten to a reactive group, is a polymer comprising from 1 to 15 ethylene glycol units; the reactive group, for coupling a linker to a carrier, is selected from the group consisting of an amine-reactive group selected from the group consisting of an isothiocyanate, an isocyanate, an acyl azide, an NHS ester, an acid chloride, an aldehyde, a glyoxal, an epoxide, an oxirane, a carbonate, an arylating agent, an imidoester, a carbodiimide, an anhydride, and combinations thereof; a thiol-reactive functional group selected from the group consisting of a haloacetyl, an alkyl halide, a maleimide, an aziridine, an acryloyl derivative, an arylating agent; a thiol-disulfide exchange reagent selected form the group consisting of a pyridyl disulfide, a TNB-thiol, a disulfide reductant, and combinations thereof; a carboxylate reactive functional groups selected from the group consisting of a diazoalkane, a diazoacetyl compound, a carbonyldiimidazole compound, and a carbodiimide; a hydroxyl-reactive functional groups selected from the group consisting of an epoxide, an oxirane, a carbonyldiimidazole, a N,N'-disuccinimidyl carbonate, a N-hydroxysuccinimidyl chloroformate, a periodate oxidizing compound, an alkyl halogen, and an isocyanate; an aldehyde and ketone reactive functional groups selected from the group consisting of a hydrazine, a Schiff base, a reductive amination product, a Mannich condensation product, and combinations thereof; an active hydrogen-reactive compound selected from the group consisting of a diazonium derivative, a Mannich condensation product, an iodination reaction product, and combinations thereof; a photoreactive chemical functional group selected from the group consisting of an aryl azide, a halogenated aryl azide, a benzophonone, a diazo compound, a diazirine derivative, and combinations thereof; the carrier is selected from the group consisting of an amino acid, a polypeptide, a protein, a nucleoside, a nucleotide, a nucleotide chain, a nucleic acid, DNA, RNA, mRNA, a polymer, aminoalkyl agarose, aminopropyl glass and crosslinked dextran; m, n, o and p are 1.