Leveraging CI-H Mass Defect Plots for the Identification of Halogenated Organic Contaminants
Poster Oct 30, 2014
Jonathan D. Byer, Mehran Alaee, Karl Jobst, Grazina Pacepavicius, Joe Binkley
Time-of-flight mass spectrometry (TOFMS) is unsurpassed for non-target analysis because full range mass spectra are acquired simultaneously with minimal mass bias at acquisition rates suitable for narrow gas chromatographic peaks. This provides a number of advantages, including the possibility of deconvolving chromatographic interferences using modern software, further enhancing the ability to isolate and identify a greater number of compounds. Mass defect is the difference between the nominal and exact masses of a compound or its fragments. Halogenated compounds have characteristic mass defects and isotope patterns that make them readily distinguishable from most other compound classes.
Mass defect (Cl-H) can be calculated according to the following equations, where the IUPAC mass is the observed mass and the scaling factor for chlorine substituted for hydrogen equals 34/33.960479:
Cl-H Scaled Mass = IUPAC Mass × Scaling Factor
Cl-H Mass Defect = Cl-H Scaled Mass – Nominal Cl-H Scaled Mass
In this study we used non-target analysis in the form of Cl-H mass defect plots, to identify halogenated contaminants in eels (Anguillia rostrata) from Lake Ontario, Canada.