Combining Headspace Solid-Phase Microextraction with Internal Benchmarking to Determine the Elimination Kinetics of Hydrophobic UVCBs

Abstract

Substances classified as unknown or variable composition, complex reaction products or biological origin (UVCB) present a challenge for environmental hazard and risk assessment. Here, we present a novel approach for whole-substance bioconcentration testing applied to cedarwood oilan essential oil composed of volatile, hydrophobic organic chemicals. The method yields whole-body elimination rate constants for a mixture of constituents. Our approach combines in vivo dietary fish exposure with internal benchmarking and headspace solid-phase microextraction (HS-SPME) equilibrium sampling followed by suspectscreening analysis. We quantified depuration rate constants of 13 individual cedarwood oil constituents based on relative peak areas using gas chromatography (GC) coupled with Orbitrap-mass spectrometry (MS) and GC triple-quadrupole (QqQ)-MS. For seven constituents with available analytical standards, we compared the rate constants to the results obtained from solvent extraction, clean-up, and targeted GC−MS analysis. The HS-SPME sampling approach allowed for automated sample extraction and analyte enrichment while minimizing evaporative losses of the volatile target analytes and reducing matrix interferences from low-volatility organics. The suspect-screening analysis enabled the quantification of constituents without available analytical standards, while the internal benchmarking significantly reduced variability from differences in delivered dose and analytical variability between the samples.

The Next Frontier of Environmental Unknowns: Substances of Unknown or Variable Composition, Complex Reaction Products, or Biological Materials (UVCBs)

“…The recommended approach has been to consider the bioaccumulative properties of a UVCB’s representative/main constituents instead of those of the whole substance itself. Bioconcentration factors (BCFs) were successfully determined for the main constituents of “cedarwood Virginia oil” (CASRN 8000-27-9) in rainbow trout this way, and continued work by the same authors developed an analytical technique within a suspect-screening approach that circumvents the need to have a priori knowledge of constituent identities and available analytical standards . Several technical substance mixtures of chlorinated paraffins, typically already subdivided according to chain length, were found to be bioaccumulative in Daphnia magna …”

“…Bioconcentration factors (BCFs) were successfully determined for the main constituents of "cedarwood Virginia oil" (CASRN 8000-27-9) in rainbow trout this way, 120 and continued work by the same authors developed an analytical technique within a suspect-screening approach that circumvents the need to have a priori knowledge of constituent identities and available analytical standards. 121 Several technical substance mixtures of chlorinated paraffins, typically already subdivided according to chain length, were found to be bioaccumulative in Daphnia magna. 122 An extended discussion of measuring UVCB bioaccumulation is available elsewhere.…”

Development of a fully automated analytical platform based on static headspace‐gas chromatography‐tandem mass spectrometry for the analysis of five N‐nitrosamines in dried aquatic products of animal origin

“…In the present study, three factors had a significant impact on each target analyte. 29 The equilibrium time and temperature of vials were the decisive parameters for volatile compounds released by the headspace technique. Volatile compounds should be fully vaporized and achieved to that stable equilibrium in gas phase.…”