title: Sequestering ability of some chelating agents towards methylmercury(II).
abstract: A study on the interactions between CH(3)Hg(+) and some S, N and O donor ligands (2-mercaptopropanoic acid (thiolactic acid (H(2)TLA)), 3-mercaptopropanoic acid (H(2)MPA), 2-mercaptosuccinic acid (thiomalic acid (H(3)TMA)), D,L-penicillamine (H(2)PSH), L-cysteine (H(2)CYS), glutathione (H(3)GSH), N,N'-bis(3-aminopropyl)-1-4-diaminobutane (spermine (SPER)), 1,2,3,4,5,6-benzenehexacarboxylic acid (mellitic acid (H(6)MLT)) and ethylenediaminetetraacetic acid (H(4)EDTA)) is reported. The speciation models in aqueous solution and the possible structures of the complexes formed are discussed on the basis of potentiometric, calorimetric, UV spectrophotometric and electrospray mass spectrometric results. For the CH(3)Hg(+)-S donor ligand systems, the formation of ML(1-z) and MLH(2-z) complex species is observed, together with a diprotonated MLH(2)(3-z) species for CYS(2-), PSH(2-) and GSH(3-) and the mixed hydrolytic one ML(OH)(-z) for TLA(2-) and MPA(2-). The dependence of the stability on ionic strength and on temperature is also analysed. In the other CH(3)Hg(+)-L systems (L = MLT(6-), SPER and EDTA(4-)), ML(1-z), MLH(2-z) and MLH(2)(3-z) complex species are formed, together with the MLH(3)(4-z) species for SPER, the mixed hydrolytic ML(OH)(-z) one for SPER and EDTA, and the M(2)L(2-z) for EDTA only. On the basis of the speciation models proposed, the sequestering ability of the ligands towards methylmercury(II) cation is evaluated. All S donor ligands show a good sequestering power (at 10(-11) mol L(-1) level, in the pH range 4 to 8) following the trend MPA(2-) < PSH(2-) < GSH(3-) < TLA(2-) < CYS(2-) < TMA(3-), while significantly lower is the sequestering ability of MLT, SPER and EDTA (at 10(-3)-10(-5) mol L(-1) level, in the pH range 4 to 8).
authors.affiliation: Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica, Università di Messina, Messina, Italy.
authors.forename: Gabriella
authors.initials: G
authors.lastname: Falcone
authors.forename: Claudia
authors.initials: C
authors.lastname: Foti
authors.forename: Antonio
authors.initials: A
authors.lastname: Gianguzza
authors.forename: Ottavia
authors.initials: O
authors.lastname: Giuffrè
authors.forename: Anna
authors.initials: A
authors.lastname: Napoli
authors.forename: Alberto
authors.initials: A
authors.lastname: Pettignano
authors.forename: Daniela
authors.initials: D
authors.lastname: Piazzese
mesh_terms: D002614:Chelating Agents / Q000737:chemistry*; D004785:Environmental Pollutants / Q000737:chemistry; D052918:Environmental Restoration and Remediation; D007700:Kinetics; D008767:Methylmercury Compounds; D015394:Molecular Structure
chemical_list: D002614:Chelating Agents; D004785:Environmental Pollutants; D008767:Methylmercury Compounds