title: Linear modeling of the soil-water partition coefficient normalized to organic carbon content by reversed-phase thin-layer chromatography.
abstract: Soil-water partition coefficient normalized to the organic carbon content (KOC) is one of the crucial properties influencing the fate of organic compounds in the environment. Chromatographic methods are well established alternative for direct sorption techniques used for KOC determination. The present work proposes reversed-phase thin-layer chromatography (RP-TLC) as a simpler, yet equally accurate method as officially recommended HPLC technique. Several TLC systems were studied including octadecyl-(RP18) and cyano-(CN) modified silica layers in combination with methanol-water and acetonitrile-water mixtures as mobile phases. In total 50 compounds of different molecular shape, size, and various ability to establish specific interactions were selected (phenols, beznodiazepines, triazine herbicides, and polyaromatic hydrocarbons). Calibration set of 29 compounds with known logKOC values determined by sorption experiments was used to build simple univariate calibrations, Principal Component Regression (PCR) and Partial Least Squares (PLS) models between logKOC and TLC retention parameters. Models exhibit good statistical performance, indicating that CN-layers contribute better to logKOC modeling than RP18-silica. The most promising TLC methods, officially recommended HPLC method, and four in silico estimation approaches have been compared by non-parametric Sum of Ranking Differences approach (SRD). The best estimations of logKOC values were achieved by simple univariate calibration of TLC retention data involving CN-silica layers and moderate content of methanol (40-50%v/v). They were ranked far well compared to the officially recommended HPLC method which was ranked in the middle. The worst estimates have been obtained from in silico computations based on octanol-water partition coefficient. Linear Solvation Energy Relationship study revealed that increased polarity of CN-layers over RP18 in combination with methanol-water mixtures is the key to better modeling of logKOC through significant diminishing of dipolar and proton accepting influence of the mobile phase as well as enhancing molar refractivity in excess of the chromatographic systems.
authors.affiliation: Faculty of Chemistry, University of Belgrade, Studentski trg 12-16, P.O. Box 51, 11158 Belgrade, Serbia. Electronic address: andric@chem.bg.ac.rs.
authors.forename: Filip
authors.initials: F
authors.lastname: Andrić
authors.affiliation: Institute of Chemistry, Technology and Metallurgy, Njegoševa 12, 11000 Belgrade, Serbia.
authors.forename: Sandra
authors.initials: S
authors.lastname: Šegan
authors.affiliation: Innovation center Faculty of Chemistry Ltd, Studentski trg 12-6, 11000 Belgrade, Serbia.
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Dramićanin
authors.affiliation: AIC Tamiš, Novoseljanski put 33, 26000 Pančevo, Serbia.
authors.forename: Helena
authors.initials: H
authors.lastname: Majstorović
authors.affiliation: Faculty of Chemistry, University of Belgrade, Studentski trg 12-16, P.O. Box 51, 11158 Belgrade, Serbia.
authors.forename: Dušanka
authors.initials: D
authors.lastname: Milojković-Opsenica
mesh_terms: D000097:Acetonitriles / Q000737:chemistry; D002138:Calibration; D002244:Carbon / Q000032:analysis* / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D056148:Chromatography, Reverse-Phase / Q000379:methods*; D002855:Chromatography, Thin Layer / Q000379:methods*; D016014:Linear Models; D000432:Methanol / Q000737:chemistry; D000442:Octanols / Q000737:chemistry; D009930:Organic Chemicals / Q000032:analysis* / Q000737:chemistry; D012987:Soil / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D000097:Acetonitriles; D000442:Octanols; D009930:Organic Chemicals; D012987:Soil; D014867:Water; D002244:Carbon; D000432:Methanol; C032159:acetonitrile
keywords: Benzodiazepines; Multivariate regression methods; Polycyclic aromatic hydrocarbons (PAHs); Reversed-phase thin-layer chromatography (RP-TLC); Soil-water partition coefficient; Sum of Ranking Differences (SRD)