Accurate-mass identification of chlorinated and brominated products of 4-nonylphenol, nonylphenol dimers, and other endocrine disrupters

LC/ToF-MS was used to identify new chlorination and bromination products of 4-nonylphenol (4-NP), such as 4-NPBr2, 4-NPBrCl, 4-NP dimer (2 isomers), 4-NPCl dimer (2 isomers), 4-NPBr dimer, and a series of methoxy bromo and chloro 4-NPs from a laboratory study of nonylphenol chlorination. The identification procedure used the exact mass, exact mass of the isotope cluster, and their relative intensities, at an average mass accuracy of approximately 1 ppm. The products were produced by a simulated study of industrial cleaning procedures where 4-NP, nonylphenol ethoxylate (NPEO-1 and 2), and nonylphenol carboxylate (NPEC-1) were in contact with sodium hypochlorite solutions (with and without bromide) of various strengths (possible environmental scenarios) at neutral pH. The formation of the products was measured as a function of chlorine concentration, and it was found that 4-NP was the most reactive, producing 4-NPCl, 4-NPCl2, 4-NP (dimers), and the 4-NPCl (dimers). In the presence of bromide ions, a mixture results with products of 4-NPBr2, 4-NPCl, 4-NPCl2, 4-NPBrCl, 4-NPBr, and a 4-NPBr dimer. Less reactive to halogenation was NPEO, which formed only the monochloro and monobromo products, and the least reactive was NPEC. A simple stereochemical model is used to explain halogenation reactivity for the family of 4-NPs and NPEOs at neutral pH. The presence of halogenated 4-NP dimers (bromo and chloro diphenyl ethers) is discussed as a possible source of new endocrine disrupters.