13C- and 15N‑Isotope Analysis of Desphenylchloridazon by Liquid Chromatography−Isotope-Ratio Mass Spectrometry and Derivatization Gas Chromatography−Isotope-Ratio Mass Spectrometry
Author(s)
Melsbach, Aileen
Lihl, Christina
Hofstetter, Thomas B.
Elsener, Martin
Date issued
January 2019
In
Analytical Chemistry
Vol
5
No
91
From page
3412
To page
3420
Reviewed by peer
1
Abstract
The widespread application of herbicides impacts
surface water and groundwater. Metabolites (e.g., desphenylchloridazon from chloridazon) may be persistent and even more polar
than the parent herbicide, which increases the risk of groundwater
contamination. When parent herbicides are still applied, metabolites are constantly formed and may also be degraded. Evaluating
their degradation on the basis of concentration measurements is,
therefore, difficult. This study presents compound-specific stableisotope analysis (CSIA) of nitrogen- and carbon-isotope ratios at
natural abundances as an alternative analytical approach to track the
origin, formation, and degradation of desphenylchloridazon (DPC),
the major degradation product of the herbicide chloridazon.
Methods were developed and validated for carbon- and nitrogen-isotope analysis (δ13C and δ15N) of DPC by liquid
chromatography−isotope-ratio mass spectrometry (LC-IRMS) and derivatization gas chromatography−IRMS (GC-IRMS),
respectively. Injecting standards directly onto an Atlantis LC-column resulted in reproducible δ13C-isotope analysis (standard
deviation <0.5‰) by LC-IRMS with a limit of precise analysis of 996 ng of DPC on-column. Accurate and reproducible δ15N
analysis with a standard deviation of <0.4‰ was achieved by GC-IRMS after derivatization of >100 ng of DPC with 160-fold
excess of (trimethylsilyl)diazomethane. Application of the method to environmental-seepage water indicated that newly formed
DPC could be distinguished from “old” DPC by the different isotopic signatures of the two DPC sources.
surface water and groundwater. Metabolites (e.g., desphenylchloridazon from chloridazon) may be persistent and even more polar
than the parent herbicide, which increases the risk of groundwater
contamination. When parent herbicides are still applied, metabolites are constantly formed and may also be degraded. Evaluating
their degradation on the basis of concentration measurements is,
therefore, difficult. This study presents compound-specific stableisotope analysis (CSIA) of nitrogen- and carbon-isotope ratios at
natural abundances as an alternative analytical approach to track the
origin, formation, and degradation of desphenylchloridazon (DPC),
the major degradation product of the herbicide chloridazon.
Methods were developed and validated for carbon- and nitrogen-isotope analysis (δ13C and δ15N) of DPC by liquid
chromatography−isotope-ratio mass spectrometry (LC-IRMS) and derivatization gas chromatography−IRMS (GC-IRMS),
respectively. Injecting standards directly onto an Atlantis LC-column resulted in reproducible δ13C-isotope analysis (standard
deviation <0.5‰) by LC-IRMS with a limit of precise analysis of 996 ng of DPC on-column. Accurate and reproducible δ15N
analysis with a standard deviation of <0.4‰ was achieved by GC-IRMS after derivatization of >100 ng of DPC with 160-fold
excess of (trimethylsilyl)diazomethane. Application of the method to environmental-seepage water indicated that newly formed
DPC could be distinguished from “old” DPC by the different isotopic signatures of the two DPC sources.
Publication type
journal article
File(s)