Identification of Potential Novel Bioaccumulative and Persistent Chemicals in Sediments from Ontario (Canada) Using Scripting Approaches with GC×GC-TOF MS Analysis

Abstract

This work describes a single and fast approach using a filtering script as a means of prioritizing sample processing of data acquired by GC×GC-TOF MS for the identification of potentially novel persistent and bioaccumulative halogenated chemicals. The proposed script is based on the recognition of a generic halogenated isotope cluster pattern that allows for the simultaneous detection of chlorinated, brominated, or mixed halogen-substituted compounds in a single classification. Once developed, the script was applied to the identification of organohalogens in stream sediments collected across the southern region of Ontario (Canada). Classified peaks were first compared with available analytical standards and reference libraries to confirm the known chemicals. Unknown potential persistent organic pollutants (POPs) were evaluated for occurrence within the samples and high resolution mass spectrometry was used in order to identify some of the most prevalent compounds in the samples and resulting in the identification of three decachlorinated dechlorane analogs (C18H14Cl10), two undecachlorinated dechlorane species (C18H13Cl11), and a novel mixed chloro/bromo-carbazole (C12H5NCl2Br2) in a number of sediments analyzed. Relative peak abundances of these unknown halogenated compounds were in the same order of magnitude or slightly higher than levels observed for conventional POPs detected in the samples.

Halogenated indigo dyes: A likely source of 1,3,6,8-tetrabromocarbazole and some other halogenated carbazoles in the environment

“…The formation of 1,8-dibromo-3,6-dichlorocarbazole, a compound measured in sediment samples in southern Ontario, Canada (Pena-Abaurrea et al, 2014a), can be explained by the presence of a carbazole impurity in the manufacture of the dye 7,7 0 -dibromo-5,5 0 -dichloroindigo (Vat Blue 37) as the halogen substitution pattern in 1,8,-dibromo-3,6-dichlorocarbazole matches exactly with the halogen substitution pattern in 7,7 0 -dibromo-5,5 0 -dichloroindigo. In the manufacture of 7,7 0 -dibromo-5,5 0 -dichloroindigo, 5,5-dichloroindigo is first prepared by chlorination of indigo or produced directly from 4-chloroaniline as the starting material.…”

“…1,3,6,8-Tetrabromocarbazole, and lesser amounts of tribromocarbazole and pentabromocarbazole were measured in sediment from Lake Michigan, USA (Zhu and Hites, 2005). 1,8-Dibromo-3,6-dichlorocarbazole was measured in stream sediments from Southern Ontario, Canada (Pena-Abaurrea et al, 2014a). A number of halogenated carbazoles, including those containing an iodo-substituent, were measured in sediment from the Great Lakes, USA (Guo et al, 2014).…”

“…A toxic equivalency factor (TEF) of 0.0016 was found for 1,8-dibromo-3,6-dichlorocarbazole (Pena-Abaurrea et al, 2014b), positioning the toxicity of this particular halogenated carbazole between that of 1,2,3,4,6,7,8-heptachlorodibenzodioxin (0.01) and octachlorodibenzodioxin (0.0003) (U.S. EPA 2010). It is likely that many halogenated carbazoles have been missed in historical sample analyses as the common utilization of acidic media in sample cleanup procedures was found to remove halogenated carbazoles that did not contain a halogen in the 1-and 8-positions (Pena-Abaurrea et al, 2014a). The combination of commonly used laboratory procedures that would preclude the detection of some halogenated carbazoles and the recently demonstrated toxicological potential and persistence provides impetus for a greater focus on these emerging contaminants.…”

Quantitative profiling of perfluoroalkyl substances by ultrahigh-performance liquid chromatography and hybrid quadrupole time-of-flight mass spectrometry

“…Furthermore, travel blanks were performed. The method was validated by calculating linearity, matrix effect, limits of quantification (LOQs), precision as repeatability and within-lab reproducibility, and recovery as widely recommended [1,22,26]. The LOQ was estimated by injecting decreasing concentrations of standards and measuring the response to find the concentrations that would give a UHPLC peak height value 1.0×10 4 as recommended elsewhere [24,30].…”

“…The problem of target screening is that a number of related compounds remain undetected in the sample just because they were not selected a priori as the analyte [24]. The ability to obtain mass spectra with a very high degree of mass accuracy at sufficient mass resolutions and high sensitivity opens the possibility for combining both non-target and target quantification [26][27][28].…”