title: Effect of copper ions on the degradation of thiram in aqueous solution: identification of degradation products by HPLC-MS/MS.
abstract: The aim of this work was to examine the effect of Cu(II) on the degradation of thiram (Thi) in aqueous solutions, since the literature focused on this effect is scarce and copper based fungicides can be applied together with thiram or during the same season to agricultural crops. The effect of Cu(II) on the degradation of thiram was followed by both UV-vis and HPLC-MS/MS. When thiram is dissolved in pure water its degradation occurs very slowly, being negligible during the first 7 days. However, the presence of Cu(II) has a strong influence on the thiram degradation in aqueous solutions along time. In the presence of an excess of Cu(II), a [CuThi](2+) complex is initially formed which degrades into a complex formed between the dimethyldithiocarbamate anion (DMDTC) and Cu(II) ion, [Cu(DMDTC)](+). This complex further degrades leading to other copper complexes which were identified for the first time, by MS(n). The results obtained in the present work also demonstrated that a redox reaction involving DMDTC anions and Cu(II) ions gives rise to the formation of a Thi-Cu(I) complex. Finally, some of the complexes resulting from the degradation of [CuThi](2+) are quite persistent in solution for long periods of time (>1 month).
authors: Instituto Politécnico de Coimbra, ESAC, DCE, Rua Pedro Nunes, 3030-199 Coimbra, Portugal; CERNAS, Campus da ESAC, Bencanta, 3040-316 Coimbra, Portugal.
authors: Olga M S
authors: OM
authors: Filipe
authors: CICECO, Department of Chemistry, Universityof Aveiro, 3810-193 Aveiro, Portugal.
authors: Sónia A O
authors: SA
authors: Santos
authors: QOPNA, Department of Chemistry, Universityof Aveiro, 3810-193 Aveiro, Portugal.
authors: M Rosário M
authors: MR
authors: Domingues
authors: Instituto Politécnico de Coimbra, ESAC, DCE, Rua Pedro Nunes, 3030-199 Coimbra, Portugal; CERNAS, Campus da ESAC, Bencanta, 3040-316 Coimbra, Portugal.
authors: Maria M
authors: MM
authors: Vidal
authors: CICECO, Department of Chemistry, Universityof Aveiro, 3810-193 Aveiro, Portugal.
authors: Armando J D
authors: AJ
authors: Silvestre
authors: CESAM, Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal. Electronic address: edsantos@ua.pt.
authors: Eduarda B H
authors: EB
authors: Santos
mesh_terms: D002851:Chromatography, High Pressure Liquid; D003300:Copper / Q000737:chemistry*; D005659:Fungicides, Industrial / Q000737:chemistry*; D013058:Mass Spectrometry; D010573:Pesticide Residues; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet; D013893:Thiram / Q000737:chemistry*; D014867:Water
chemical_list: D005659:Fungicides, Industrial; D010573:Pesticide Residues; D012996:Solutions; D014867:Water; D013893:Thiram; D003300:Copper
keywords: Aqueous solutions; Copper ions; Dimethyldithiocarbamate; HPLC-UV–MS(n); Thiram degradation; UV–vis spectrophotometry