An optical material for the detection of trace S₂O₃^2- in milk based on a copper complex

A novel S₂O₃^2- luminescent sensor (Cu²⁺-p-CPIP) was developed and the presence of S₂O₃^2- caused an obvious fluorescence enhancement at 420 nm upon excitation at 330 nm, which could be distinguished with the naked eye under a UV lamp. Remarkably, the compound exhibited excellent selective and sensitive response to S₂O₃^2- over other common anions with a micromolar limit of detection (0.442 μM) in DMSO/H₂O (v/v, 1:1) buffer. The absorbance intensity and the color of Cu²⁺-p -CPIP solution changed gradually with the increase of S₂O₃^2- concentration. The proposed method was applied to the determination of S₂O₃^2- in milk samples and the recoveries were 97.5-105%. The preparation of Cu²⁺-p -CPIP exhibited the quick, simple and facile advantages. The results showed that Cu²⁺-p -CPIP can be a good candidate for simple, rapid and sensitive colorimetric detection of S₂O₃^2- in aqueous solution.