Experimental Determination of LSER Parameters for a Set of 76 Diverse Pesticides and Pharmaceuticals

Abstract

Linear solvation energy relationships (LSERs) have more recently been proposed as the method of choice to describe and/or predict the partitioning behavior of neutral organic compounds over a large range of environmental matrices and for a broad variety of compounds in a consistent manner. However, when dealing with more complex, polar compounds with multiple functional groups, it has also been noted that there is a severe lack of substance descriptors quantifying the different intermolecular interactions that these compounds may undergo. In this study, we used a system of eight reversed phase, normal phase, and hydrophilic interaction HPLC systems to determine the substance descriptors for H-bond donor (A) and acceptor (B) interactions and for polarizability and dipolarity (S) for a set of 76 complex compounds containing multiple functional groups, comprising mainly pesticides and some pharmaceuticals. The obtained substance descriptors for most compounds are unique in that values of A, S, and B are high and lie at the very upper end of the numerical range of currently known substance descriptors. The substance descriptors have been cross-compared against literature values of the octanol-water (Kow) and air-water (Kaw) partition coefficients and against a set of heptan-methanol partition coefficients (Khm) experimentally determined with a consistent methodology herein. The comparison confirmed plausibility of the substance descriptors of all except six tested compounds. The newly determined substance descriptors promise to be highly valuable in chemicalfate modeling, allowing, in conjunction with available phase descriptors, for a better representation of partitioning of polar compounds in those models. The results also reveal a systematic deviation of the log Kow values predicted with our substance descriptors from the literature values. The deviation points toward a possible problem when existing LSER equations are applied to polar, multifunctional compounds with high values of A, S, and B. Hence, the substance descriptors determined herein should also be helpful in revisiting the validity of existing LSERs for complex, polar compounds.

Determination of LFER Descriptors of 30 Cations of Ionic Liquids—Progress in Understanding Their Molecular Interaction Potentials

“…The standard error of the regressions ranged from 0.064 to 0.087 log units. This is deemed reasonably low and is comparable to the error range of a 78 compound training set measured on eight HPLC systems as presented by Tülp et al [29] All e values are in the range between 0.065 and 0.723 log units. Among them, the e values of the Diol column systems are generally larger than for other systems, while the e value of the RP-Select B system with ACN is close to zero.…”

“…For these, at least three HPLC systems with different interactions (orthogonal) controlling the retention would be necessary. [29] However, it is difficult to find three systems with completely orthogonal stationary phases. Thus, we employed five HPLC systems, RP-select B-ACN, RP-select B-MeOH, Cyan-MeOH, Diol-ACN, and Diol-MeOH, which we deem sufficient to assess these LFER descriptors.…”

“…It has been successfully used to determine solute descriptors for neutral molecules. [29][30] A wide spectrum of molecular interaction potentials can be covered by various stationary phases. When salts are added to the mobile phase, which is frequently done in order to buffer the pH to the desired value, counterion effects can be neglected in analytical investigations of the cation.…”

Global Water Pollution and Human Health

“…The major analytical difficulties are encountered with more complex, multifunctional polar chemicals, which include many of the biologically active compounds-such as modern pesticides, biocides, and pharmaceuticals (32,33). The same holds for the quantification of the environmental partitioning of organic pollutants (e.g., sorption from water to particles, soils, or sediments), which is most difficult for polar, complex organic chemicalsincluding those exhibiting ionizable functional groups (34,35).…”

Linear modeling of the soil-water partition coefficient normalized to organic carbon content by reversed-phase thin-layer chromatography

“…negative values of a, b, and s, positive values of e and v, and the highest absolute values of a, b, and v. [46,47] This clearly demonstrates the significant role of aqueous mobile phase and organic modifier, their strong contribution to formation of hydrogen bonds with solute molecules, and significant resistance to formation of an empty space for incorporation of a transferring molecule from stationary phase [30,46,47]. Dissimilarities and similarities among two contrasting LSER models i and j are further calculated using Euclidian distance [49] and Ishihama's and Asakawa's [48,49] cosine similarity measure (cos θ) (Eqs.…”