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Occurrence and degradation of chiral nonylphenol isomers in sewage and soils

Aim

Studies on the fate of structural isomers and enantiomers are required in order to improve our knowledge of the biological and environmental behaviour of the endocrine disrupting chemical 4-nonylphenol (NP). Theoretically, 211 constitutional NP isomers are existing. Many of these isomers possess up to three chiral C-atoms, so that in total up to 550 compounds can occur. Recent studies have shown that the estrogenic effects of the individual NP isomers are strongly dependent on the structure of the alkyl side chain. Log Kow values for representative NP isomers range from 4.7 to 5.6, suggesting differences in the bioconcentration potential among NP isomers. Therefore, isomer and enantiomer-specific determination of NP is of great interest in NP research. The aim of this project is to investigate the origin and fate of selected chiral NP isomers in the aquatic environment and in soils.

big_140_struktur

Structure of two chiral NP isomers NP,,112,, (4-1-ethyl-1,4-dimethylpentyl)phenol) and NP,,35,, (4-(1,1,2-trimethylhexyl)phenol)

 

Approach

A chiral GC-MS method was developed in order to achieve this. Concentration and enantiomer ratio (ER) of the selected chiral NP isomers were determined, indicating enantioselective degradation. Influent and effluent samples from wastewater treatment plant were pre-concentrated using liquid-liquid extraction (LLE) and cleaned up by solid-phase extraction (SPE). Then, the analytes were derivatized and analyzed by chiral gas chromatography coupled with mass spectrometry (GC-MS). In addition, pure enantiomers of the NP isomers were isolated by a chiral semi-preparative HPLC method, allowing quantitation of the corresponding enantiomers and further biological investigation.

big_140_gc-ms

GC-MS-SIM chromatograms (m/z 163 and m/z 149 methylated sample) of an influent sample from the WWTP investigated. *ER: enantiomer ratio

 

Results

The enantiomeric determination of the target isomers was successfully carried out in influent and effluent waters of WWTPs. The enantiomeric ratio of enantiomers of NP112 and NP35 is close to 1.0 in most of the samples. However, in one influent examined, an enantiomer ratio of 1.7 was determined for both isomers.
The degradation of NP112 in different soils and the formation of a nitro-nonylphenol metabolite was determined. The degradation followed bi-exponential order kinetics, with half life of less than 5 days in both soils. and the nitro-metabolite was more persistent than its parent compound. Results of E-screen assay revealed that the nitro-NP112 has oestrogenic potency of 85% of that of NP112.
The absolute configurations of the synthesized NP35 were determined by an X-ray crystallographic study of the (2)-camphanoyl derivative. The estrogenic potencies of the S and R enantiomers were tested by the E-screen assay. A slight difference was observed in the relative proliferative effect between the S enantiomer and R enantiomer.

 

Publications

  1. Zhang, H.; Oppel, I.M.; Spiteller, M.; Guenther, K.; Boehmler, G.; Zuehlke, S. (2009):
    "Enantiomers of a nonylphenol isomer: absolute configurations and estrogenic potencies" Chirality, 21, 271-275.

  2. Zhang, H.; Spiteller, M.; Guenther, K.; Boehmler, G.; Zühlke, S. (2009):
    "Degradation of a Chiral Nonylphenol Isomer in Two Agricultural Soils" Environmental Pollution, 157(6), 1904-1910.

  3. Zhang, H.; Zühlke, S.; Günther, K.; Spiteller, M. (2007):
    "Enantioselective Separation and Determination of Single Nonylphenol Isomers" Chemosphere, 66, 594-602.



Sub content

Contact

Prof. Dr. Dr. h.c. Michael Spiteller
Tel.: 0231 755-4080
Dr. Sebastian Z├╝hlke
Head of Laboratory
Tel.: 0231 755-4088