title: Ultraviolet degradation of procymidone--structural characterization by gas chromatography coupled with mass spectrometry and potential toxicity of photoproducts using in silico tests.
abstract: BACKGROUND
  Procymidone is a dicarboximide fungicide mainly used for vineyard protection but also for different crops. The structural elucidation of by-products arising from the UV-visible photodegradation of procymidone has been investigated by gas chromatography coupled with mass spectrometry. The potential toxicities of photoproducts were estimated by in silico tests.
  
  
  METHODS
  Aqueous solutions of procymidone were irradiated for up to 90 min in a self-made reactor equipped with a mercury lamp. Analyses were carried out on a gas chromatograph coupled with an ion trap mass spectrometer operated in electron ionization and methanol positive chemical ionization. Multistage collision-induced dissociation (CID) experiments were performed to establish dissociation pathways of ions. Toxicities of byproducts were estimated using the QSAR T.E.S.T. program.
  
  
  RESULTS
  Sixteen photoproducts were investigated. Chemical structures were proposed mainly based on the interpretation of multistage CID experiments, but also on their relative retention times and kinetics data. These structures enabled photodegradation pathways to be suggested. Only three photoproducts remain present after 90 min of irradiation. Among them, 3,5-dichloroaniline presents a predicted rat LD50 toxicity about ten times greater than that of procymidone.
  
  
  CONCLUSIONS
  3,5-Dichloroaniline is the only photoproduct reported in previous articles. Eight by-products among the sixteen characterized might be as toxic, if not more, than procymidone itself considering the QSAR-predicted rat LD50.
authors.affiliation: Laboratoire des Mécanismes Réactionnels UMR-7651, Ecole Polytechnique, Palaiseau, France.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Rifai
authors.forename: Yasmine
authors.initials: Y
authors.lastname: Souissi
authors.forename: Christophe
authors.initials: C
authors.lastname: Genty
authors.forename: Carine
authors.initials: C
authors.lastname: Clavaguera
authors.forename: Sophie
authors.initials: S
authors.lastname: Bourcier
authors.forename: Farouk
authors.initials: F
authors.lastname: Jaber
authors.forename: Stéphane
authors.initials: S
authors.lastname: Bouchonnet
mesh_terms: D000818:Animals; D001643:Bridged Bicyclo Compounds / Q000737:chemistry / Q000633:toxicity*; D005659:Fungicides, Industrial / Q000737:chemistry* / Q000633:toxicity*; D008401:Gas Chromatography-Mass Spectrometry; D007700:Kinetics; D008297:Male; D015394:Molecular Structure; D010782:Photolysis; D021281:Quantitative Structure-Activity Relationship; D051381:Rats; D014466:Ultraviolet Rays
chemical_list: D001643:Bridged Bicyclo Compounds; D005659:Fungicides, Industrial; C035988:procymidone