Multi-isotope characterization of 4,4'-DDT isolated from sediment samples via Orbitrap-IRMS

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Mass Spectrometry

Background:

• Dichlorodiphenyltrichloroethane (DDT) is a persistent environmental contaminant with significant toxicity.
• Stable isotopes are valuable tools for tracing the environmental pathways of contaminants like DDT.
• Accurate isotopic measurements are crucial for understanding DDT's environmental behavior and degradation.

Purpose of the Study:

• To develop and validate an Orbitrap Isotope Ratio Mass Spectrometry (Orbitrap-IRMS) method for measuring stable isotopes in Dichlorodiphenyltrichloroethane (DDT).
• To apply the developed method to analyze DDT in environmental samples, specifically sediment from a contaminated site.
• To assess the potential for isotopic analysis to fingerprint DDT sources and estimate degradation levels.

Main Methods:

• Utilized Orbitrap Isotope Ratio Mass Spectrometry (Orbitrap-IRMS) for high-precision isotopic analysis.
• Measured isotopic content of two specific Dichlorodiphenyltrichloroethane (DDT) fragment ions: m/z = 235 [M+ - CCl3] and m/z = 316 [M+ - HCl].
• Applied the method to both commercial 4,4'-DDT standards and DDT extracted from sediment samples near the White Point sewage outflow.

Main Results:

• The Orbitrap-IRMS method achieved precise measurements for Dichlorodiphenyltrichloroethane (DDT) standards with small sample sizes.
• Analysis of sediment samples showed isotopic enrichment in δ13C and δ37Cl for the [M+ - CCl3] fragment, suggesting potential degradation.
• The study established an upper bound of 66% for Dichlorodiphenyltrichloroethane (DDT) degradation based on isotopic data.

Conclusions:

• The developed Orbitrap-IRMS method is effective for tracing Dichlorodiphenyltrichloroethane (DDT) through isotopic analysis.
• Isotopic fingerprinting of DDT fragments provides valuable insights into its environmental fate and potential degradation processes.
• Further investigation into multiply substituted isotopologues is warranted to enhance fingerprinting capabilities and degradation assessment.