The invention provides a novel method of labeling oligonucleotides, with reporter moieties, including but not limited to, quenchers, fluorophores, biotin, digoxigenin, peptides and proteins. In addition, this invention provides a method of detecting hybridization of oligonucleotides. This invention also provides novel azo quenchers having the general formula shown below. ##STR00001## The invention further provides compositions comprising labeled oligonucleotides and solid supports. The invention also provides kits comprising at least one composition of the present invention.