title: Hard- and soft-modeling approaches for resolution of complex formation of Co2+ and Ni2+ with glycine.
abstract: Principal component analysis (PCA) was used to obtain information about the number of components in the complex formation equilibria of Co(2+) and Ni(2+) with glycine (Gly). In order to obtain a clearer insight into these complex formation systems, multivariate curve resolution-alternating least squares (MCR-ALS) was used. Using MCR-ALS as a soft-modeling method, well-defined concentration and spectral profiles were obtained under unimodality, non-negativity, and closure constraints. Based on the obtained results, an equilibrium model was proposed and subsequently, a hard-modeling method was used to resolve the complex formation equilibria completely. Due to the presence of multiple equilibria, the resolution of such systems is very difficult. The Co-Gly system was best described by a model consisting of M(GlyH), M(Gly), M(Gly)(2), M(Gly)(2)H, and M(Gly)(3) (M = Co(2+)) with the overall stability constants determined to be 7.10 ± 0.011, 5.14 ± 0.006, 9.28 ± 0.009, 13.75 ± 0.016, and 11.10 ± 0.010, respectively. On the other hand, the system of Ni-Gly was best fitted by a model containing M(GlyH), M(Gly), M(Gly)(2), M(Gly)(3), and M(Gly)(2)(OH) (M = Ni(2+)) with overall stability constants of 10.95 ± 0.04, 6.41 ± 0.03, 11.31 ± 0.03, 15.39 ± 0.06, and 14.32 ± 0.02, respectively.
authors.affiliation: Department of Analytical Chemistry, Faculty of Chemistry, Razi University, Kermanshah, Iran. mshariati_rad@yahoo.com
authors.forename: Masoud
authors.initials: M
authors.lastname: Shariati-Rad
authors.forename: Masoumeh
authors.initials: M
authors.lastname: Hasani
authors.forename: Mojtaba
authors.initials: M
authors.lastname: Shamsipur
mesh_terms: D000042:Absorption; D003035:Cobalt / Q000737:chemistry*; D005998:Glycine / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D016018:Least-Squares Analysis; D008956:Models, Chemical; D015233:Models, Statistical; D015999:Multivariate Analysis; D009532:Nickel / Q000737:chemistry*; D025341:Principal Component Analysis; D013053:Spectrophotometry
chemical_list: D003035:Cobalt; D009532:Nickel; D005998:Glycine