Photosensitized Transformation-chemiluminescence Determination Of Chlorophenols

Chlorophenols are important chemical materials widely used in pharmaceutical, agricultural and industries. With the large-scale producing and using, chlorophenols have been largely discharged into the environment, which have caused considerable damage and threat to the ecosystem in aquatic bodies and human health.This paper mainly studied the chemiluminescence (CL) system of common chlorophenols and the mechanisms were also discussed. The main results were given as follows:. 1. A novel and sensitive flow injection CL method for the determination of 2, 4-dichlorophenol was proposed. The analyte was phototransformed on-line to a light emitting precursor using visible light in the presence of fluorescein and the CL reaction was then triggered with an oxidant N-bromosuccinimide using a two-channel flow injection manifold. The influencing factors of the CL intensity were tested. At the optimized conditions, the CL intensity responded linearly to 2, 4-DCP for concentration ranges 7.3×10-7 - 7.3×10-6mol/L and 7.3×10-6 - 7.3×10-5mol/L, respectively. The detection limit was measured to be 1.5×10-7mol/L and which can be further lowered by preconcentration with solid phase extraction technique. By testing the potential interference substances, the proposed method also exhibited good selectivity for 2, 4-DCP determination.2. The CL reaction of photosensitized 2-chlorophenol, 4-chlorophenol, 2, 4, 6–trichlorophenol and pentachlorophenol was investigated respectively. The result showed that all of the above photosensitized chlorophenols have CL phenomena and the linear relationship between chlorophenol concentration and the CL intensity was similar to that of 2, 4-dichlorophenol at the optimized conditions, which indicated that these CL precursors had similar structure. The detection limit was measured to be 8.6×10-8mol/L, 1.1×10-7, 4.6×10-8mol/L and 3.0×10-5mol/L for 2-CP, 4-CP, 2,4,6-TCP and PCP respectively and which can be further lowered by preconcentration. The CL reaction of photosensitized phenol, catechol, hydroquinone and 4-nitrophenol was also studied respectively according to the similar method. The results showed that none of these compounds tested result CL signal.3. The possible mechanism of the CL reaction was preliminarily investigated. It was suggested that the singlet oxygen formed by the photosensitized process was responsible for the phototransformation of the chlorophenol into a light emitting precursor.