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Merck

Enantioselective stable isotope analysis (ESIA) of polar herbicides.

Analytical and bioanalytical chemistry (2013-02-05)
Michael P Maier, Shiran Qiu, Martin Elsner
ABSTRAKT

Assessing the environmental fate of chiral micropollutants such as herbicides is challenging. The complexity of aquatic systems often makes it difficult to obtain hydraulic mass balances, which is a prerequisite when assessing degradation based on concentration data. Elegant alternatives are concentration-independent approaches like compound-specific isotope analysis or enantiospecific concentration analysis. Both detect degradation-induced changes from ratios of molecular species, either isotopologues or enantiomers. A combination of both-enantioselective stable isotope analysis (ESIA)-provides information on (13)C/(12)C ratios for each enantiomer separately. Recently, Badea et al. demonstrated for the first time ESIA for the insecticide α-hexachlorocyclohexane. The present study enlarges the applicability of ESIA to polar herbicides such as phenoxy acids: 4-CPP ((RS)-2-(4-chlorophenoxy)-propionic acid), mecoprop (2-(4-chloro-2-methylphenoxy)-propionic acid), and dichlorprop (2-(2,4-dichlorophenoxy)-propionic acid). Enantioselective gas chromatography-isotope ratio mass spectrometry was accomplished with derivatization prior to analysis. Precise carbon isotope analysis (2σ ≤ 0.5‰) was obtained with ≥7 ng C on column. Microbial degradation of dichlorprop, 2-(2,4-dichlorophenoxy)-propionic acid by Delftia acidovorans MC1 showed pronounced enantiomer fractionation, but no isotope fractionation. In contrast, Badea et al. observed isotope fractionation, but no enantiomeric fractionation. Hence, the two lines of evidence appear to complement each other. They may provide enhanced insight when combined as ESIA.

MATERIAŁY
Numer produktu
Marka
Opis produktu

Supelco
2,4-D, PESTANAL®, analytical standard
Supelco
2,4-D, PESTANAL®, analytical standard
Supelco
Dichloroprop-P, PESTANAL®, analytical standard
Sigma-Aldrich
4-Chloro-2-methylphenoxyacetic acid, technical, ≥95.0% (T)
Supelco
Mecoprop-P, PESTANAL®, analytical standard
Supelco
MCPA, PESTANAL®, analytical standard
Supelco
2,4-D, certified reference material, TraceCERT®, Manufactured by: Sigma-Aldrich Production GmbH, Switzerland
Supelco
Dichlorprop, PESTANAL®, analytical standard
Supelco
Mecoprop, PESTANAL®, analytical standard
Sigma-Aldrich
2,4-Dichlorophenoxyacetic acid, 97%
Sigma-Aldrich
2,4-Dichlorophenoxyacetic acid, ≥95%, crystalline
Supelco
Boron trifluoride - 1-butanol solution, ~10% in 1-butanol (∼1.3 M), for GC derivatization, LiChropur