Characterization of Chlorobenzene, Chloroaniline, Chlorophenol, and Chloronitrobenzene in Water using Dispersive Liquid-Liquid Microextraction and 1H Nuclear Magnetic Resonance Spectroscopy

This study presents a method based on Dispersive Liquid Liquid Microextraction (DLLME) for the preconcentration of chloroaniline, chlorobenzene, chlorophenol, and chloronitrobenzene structures in water for analysis by 1H Nuclear Magnetic Resonance (NMR) Spectroscopy. Chlorinated aromatic compounds are common precursors and byproducts produced during the manufacturing of many chlorinated pesticides and, as such, may often be found in the soil and groundwater at pesticide manufacturing sites. Nuclear magnetic resonance is a powerful tool for the analysis of mixtures of organic compounds and has been shown to be useful for characterizing contamination profiles at complex contaminated sites. Nevertheless, the application of NMR as a tool in analytical environmental chemistry is limited by its lower sensitivity. The use of DLLME allows for the rapid and simple extraction of organic analytes into a minimal quantity of deuterated chloroform for analysis by NMR in a single step. Compared to a direct NMR analysis of these analytes in water, DLLME is shown to produce a signal enhancement of 12 to 40×, with limits of detection of ∼0.003 mM achievable, depending on configurations. Extraction recovery ranges from 20 to 75% for chlorophenol, 80-100% for chloroaniline and chlorobenzene, and 90-100% for chloronitrobenzene. Overall, this method presents a simple, fast, and robust approach to use NMR spectroscopy as a non-targeted tool to analyze a range of groundwater contaminants in a single measurement and has potential to assist the characterization of complex contaminated sites.