Optical detection of sulphasalazine in water and food samples using a hydrophilic ionic liquid as a potential fluorescent probe mediated with copper ions

A new and selective method based on using a asymmetric hydrophilic ionic liquid 1, 3-butylimidazolium bromide [Bbim][Br] as a fluorescence probe was developed to determine sulphasalazine (SSZ) in aqueous solutions. The copper ion mediated fluorescence of the [Bbim][Br] could be significantly quenched with increasing of SSZ concentration in the presence of an anionic surfactant. The effects of several experimental parameters, such as pH of the sample solution, contact time, concentrations of ionic liquid and copper ion, as well as influence of surfactant on the fluorescence intensity were investigated and optimized. The fluorescence quenching value (ΔI) showed a good linear relationship with SSZ concentrations from 0.3 to 24 μmol L− 1 with an estimated detection limit of 0.09 μmol L− 1. The relative standard deviation (RSD%) for five replicate determinations of 4.0 μmol L− 1 SSZ was 2.1%. The results showed that the proposed method is a rapid, simple and feasible method for the determination of SSZ in aqueous samples. Finally, the proposed method was successfully applied for monitoring low level amounts of SSZ residue in tap water, honey and milk samples with satisfactory results.