Stability of a stilbene-type 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 aga inst hypochlorite, which may restrict its use and may have an adverse envir onmental 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 transitio n metal ions usually present in tap water. THE catalytic effect decreases i n the following sequence for the metal ions tested: Fe2+ much greater than Mn2+ > Cu2+ similar or equal to Fe3+. The addition of an appropriate chelat ing agent such as Dequest(R) 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.