title: Pathway of diethyl phthalate photolysis in sea-water determined by gas chromatography-mass spectrometry and compound-specific isotope analysis.
abstract: The degradation mechanism of diethyl phthalate (DEP) in natural seawater under UV irradiation was investigated using a combination of intermediates detection and determination of stable carbon isotopic fractionation. Typical intermediates identified with gas chromatography-mass spectrometry (GC-MS) were mono-ethyl phthalate (MEP) and phthalic anhydride. Stable carbon isotope signature was determined by gas chromatography coupled with isotope ratio mass spectrometry through a combustion interface (GC-C-IRMS). A profound (13)C enrichment, with a δ(13)C isotope shift of 12.3±0.3‰ (f=0.09) in residual DEP molecule, was clearly an indicator to its photolysis. The reactive position isotope enrichment factor (ε(reactive position)) and apparent kinetic isotope effects (AKIE) were -35.25±2.26‰ and 1.075, respectively, indicating that the initial reaction step was cleavage of a CO bond in DEP photolysis. Based on these observations, a degradation pathway was proposed. First, a CO bond in DEP molecule was broken to form MEP. Then, MEP was further degraded to phthalic anhydride. Our work demonstrates that compound-specific isotope analysis (CSIA), when combined with intermediates analysis, is a reliable measure to deduce the mechanism of DEP photolysis. This approach might be extended as a reference for mechanism investigation in complicated environment systems.
authors.affiliation: Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, China.
authors.forename: Xuewei
authors.initials: X
authors.lastname: Peng
authors.forename: Lijuan
authors.initials: L
authors.lastname: Feng
authors.forename: Xianguo
authors.initials: X
authors.lastname: Li
mesh_terms: D008401:Gas Chromatography-Mass Spectrometry; D007554:Isotopes; D008956:Models, Chemical; D010782:Photolysis; D010795:Phthalic Acids / Q000032:analysis* / Q000737:chemistry; D012623:Seawater / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry
chemical_list: D007554:Isotopes; D010795:Phthalic Acids; D014874:Water Pollutants, Chemical