Stability of a stilbene tyne fluorescent whitening agent against hypochlorite

E, E[4,4-bis(2 sulfostyryl)biphenyl] (DSBP) is a stilbene type fluorescent whitening agent (FWA) widely used by the textile and detergent industries. UV and fluorescence spectrophotometry are used to examine its stability against hypochlorite, which may restrict its use and may have an adverse environmental impact because a considerable fraction of the FWA used during the washing process remains in the washing liquor and is discharged into sewers. The degradation of this whitening agent is catalyzed by several transition metal ions usually present in tap water. The catalytic effect decreases in the following sequence for the metal ions tested: Fe2+χMn2+> Cu2+≃ Fe3+The addition of an appropriate chelating agent such as Dequest ® 2006 [diethyleneaminepenta(methylenephosphonic) acid] in a 20:1 mole ratio completely inhibits the process; by contrast, other complex-forming agents such as EDTA accelerate it.