Characterization of PCB Sulfate Intermediates

Melting points were measured on a Mel-Temp melting point apparatus and are uncorrected. If not stated otherwise, all PCB sulfates and the corresponding intermediates, were characterized by ¹H and ¹³C NMR spectroscopy. The NMR spectra were recorded on a Bruker Avance DRX-400 spectrometer in the University of Iowa Central NMR Research Facility (Iowa City, IA, USA). The NMR samples were prepared in CDCl₃ or CD₃OD (Cambridge Isotope Laboratories, Andover, MA), and tetramethylsilane (TMS) was used as internal standard. GC-MS analysis of TCE-PCB sulfates diester intermediates was performed in the electron impact (EI) mode on an Agilent 6890N gas chromatograph coupled with an Agilent 5975 Mass Selective Detector (Agilent Technologies, CA, USA) as reported previously (Telu et al. 2010 (link)). Only the isotopic ion with the lowest mass is reported for major fragments observed in the MS spectra. Accurate mass determinations of the PCB sulfates were performed by the High Resolution Mass Spectrometry Facility of the University of California Riverside (Riverside, CA, USA). The purity of all PCB sulfates was verified by thin layer chromatography as described previously (Li et al. 2010 (link)) prior to preparing DMSO stock solutions for cell culture experiments to ensure that no hydrolysis to the corresponding OH-PCB had occurred.