TY - JOUR
T1 - Isotope analysis method for the herbicide bromoxynil and its application to study photo-degradation processes
AU - Knossow, Nadav
AU - Siebner, Hagar
AU - Bernstein, Anat
N1 - Funding Information:
We acknowledge the Negev - Zin scholarships of the Kreitman School of Advanced Graduate Studies for supporting NK. We are grateful to Prof. Zeev Ronen, BGU, for his guiding and support. We thank Dr. Faina Gelman, GSI, for analytical support.
Publisher Copyright:
© 2020 Elsevier B.V.
PY - 2020/4/15
Y1 - 2020/4/15
N2 - Bromoxynil is an increasingly applied nitrile herbicide used for post-emergent control of annual broadleaved weeds. Compound-specific isotope analysis (CSIA) of the compound is of interest for studying its environmental fate, yet is challenging following its polar nature. We present a CSIA method for bromoxynil that includes offline thin-layer chromatography purification followed by an elemental analyzer isotope ratio mass spectrometer (EA-IRMS). This method was shown to be accurate and precise for δ13C and δ15N analysis of the compound (standard deviation of replicate standards <0.5‰). The method was applied to photodegraded samples, either radiated under laboratory condition with a UV lamp, or exposed to sunlight under environmental conditions. Dominating degradation products were similar in both cases. Nevertheless, isotope effects differed, presenting a strong inverse carbon isotope effect (εC = 4.74 ± 0.82‰) and a weak inverse nitrogen isotope effect (εN = 0.76 ± 0.12‰) for the laboratory experiment, and an insignificant carbon isotope effect (εC = 0.34 ± 0.44‰) and a normal nitrogen isotope effect (εN = −3.70 ± 0.30‰) for the natural conditions experiment. The differences in δ13C vs. δ15N enrichment trends suggest different mechanism for the two processes. Finally, the obtained dual isotope trend for natural conditions provide the basis for studying the dominance of photodegradation as a degradation route in the environment.
AB - Bromoxynil is an increasingly applied nitrile herbicide used for post-emergent control of annual broadleaved weeds. Compound-specific isotope analysis (CSIA) of the compound is of interest for studying its environmental fate, yet is challenging following its polar nature. We present a CSIA method for bromoxynil that includes offline thin-layer chromatography purification followed by an elemental analyzer isotope ratio mass spectrometer (EA-IRMS). This method was shown to be accurate and precise for δ13C and δ15N analysis of the compound (standard deviation of replicate standards <0.5‰). The method was applied to photodegraded samples, either radiated under laboratory condition with a UV lamp, or exposed to sunlight under environmental conditions. Dominating degradation products were similar in both cases. Nevertheless, isotope effects differed, presenting a strong inverse carbon isotope effect (εC = 4.74 ± 0.82‰) and a weak inverse nitrogen isotope effect (εN = 0.76 ± 0.12‰) for the laboratory experiment, and an insignificant carbon isotope effect (εC = 0.34 ± 0.44‰) and a normal nitrogen isotope effect (εN = −3.70 ± 0.30‰) for the natural conditions experiment. The differences in δ13C vs. δ15N enrichment trends suggest different mechanism for the two processes. Finally, the obtained dual isotope trend for natural conditions provide the basis for studying the dominance of photodegradation as a degradation route in the environment.
KW - CSIA
KW - EA-IRMS
KW - Pesticide
KW - Thin layer chromatography
UR - http://www.scopus.com/inward/record.url?scp=85077754869&partnerID=8YFLogxK
U2 - 10.1016/j.jhazmat.2020.122036
DO - 10.1016/j.jhazmat.2020.122036
M3 - Article
C2 - 31951995
AN - SCOPUS:85077754869
SN - 0304-3894
VL - 388
JO - Journal of Hazardous Materials
JF - Journal of Hazardous Materials
M1 - 122036
ER -