qFlamma® Black01 Carboxylic acid is an inactive form of universal dark quencher that the range of absorption covers from 400 to 800 nm with no native fluorescence. Black01 quencher displays high absorption coefficient, superb stability and aqueous solubility. A hexanoic acid is attached to Black01 quencher. qFlamma® Black01 carboxylic acid can be coupled with amines at a probe or on biomolecules by standard amide bond coupling conditions or can be utilized as a reference standard for fluorophore-quencher pair probes.