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. 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.