Application of various methods to determine the lipophilicity parameters of the selected urea pesticides as predictors of their bioaccumulation

Different lipophilicity procedures including a newly developed (based on Ościk's equation) was applied in order to compare various urea pesticides with herbicidal and also insecticidal activity, such as monolinuron, chlorotoluron, diuron, isoproturon, linuron, dimefuron, diflubenzuron, teflubenzuron and lufenuron. Lipophilicity parameters (RMWS and RMW0) of nine examined pesticides were determined on the chromatographic plates RP-8F254 with the use of methanol-water as a mobile phase. Similarity analysis enabled to group all examined pesticides depending on their lipophilic character and allowed to perform a more objective comparison of different lipophilicity parameters obtained for investigated compounds by means of thin-layer chromatography and by the use of computational methods. It was stated that with the number of fluorine in examined pesticides, the lipophilic character of insecticides and also their tendency to bioaccumulation in the living systems increases noticeably. The results of this work confirmed that a new procedure for determining the lipophilicity parameter (RMW0) by Ościk's equation could be a suitable tool in the prediction of pesticide bioaccumulation in living system and may be used as an indicator in design of new urea pesticides, which will be safe for humans and the environment.

Comprehensive evaluation of lipophilicity of biogenic amines and related compounds using different chemically bonded phases and various descriptors

The retention behavior for a series of biogenic amines and related sympathomimetic drugs has been investigated in reversed-phase thin-layer chromatography using RP-2, RP-8, RP-18W, and Diol stationary phase and mixtures of phosphate buffer (pH = 7.10) and methanol in different proportions as mobile phases. Several methodologies like arithmetic mean of experimental retention values, extrapolation to zero methanol concentration procedure and principal component analysis were applied to retention data values (R(M)) in order to determine relevant parameters (mean of R(M) - mR(M), R(M0), and scores corresponding to the first principal component - PC1/R(M) respectively) encoding information on the lipophilic behavior of compounds. High similarities in lipophilicity behavior of investigated amines were highlighted by mR(M) and PC1/R(M) lipophilicity indices for all of the studied stationary phases. The experimental results were compared with some computed lipophilicity parameters expressed as distribution coefficients at working pH (logD), partition coefficients (logP(N), logP(I), and diff(logP(N-I))) concerning both neutral and fully protonated species and difference between both species, and also with various lipophilicity values (logP) generated by different commonly used software. Significant correlations were observed between the experimental lipophilicity indices mR(M) respectively PC1/R(M) and diff(logP(N-I) ) values in all cases.

Review of advances in the thin layer chromatography of pesticides: 2006-2008

Applications of thin layer chromatography and high performance thin layer chromatography for the separation, detection, qualitative and quantitative determination, and preparatire isolation of pesticides and their metabolites are reviewed for the period from July 1, 2006 to November 1, 2008. Analyses are described for a variety of sample types and pesticide classes. In addition to references on residue and formulation analysis, studies such as pesticide-structure relationships, identification and characterization of plant pesticides, metabolism, degradation, mobility, and lipophilicity are covered. Future prospects for pesticide thin layer chromatography are also considered.