Octanol/Water Partition Coefficient of Selected Herbicides:Determination Using Shake-Flask Method and Reversed-Phase High-Performance Liquid Chromatography

摘要

For some triazines and phenylurea derivatives no reliable K_(ow)values were available from literature.The log K_(ow)values were determined directly with the shake-flask procedure and also indirectly using the reversed-phase high-performance liquid chromatography(RP-HPLC)method in the isocratic and gradient elution mode,respectively.Atrazine,as a well-investigated substance,and two herbicides of different chemical structures(acid amides)were included in this study.Both RP-HPLC methods yield log K_(ow)values comparable among themselves and identical with the shake-flask results for methabenz-thiazuron(2.5),chloroxuron(3.8),sebutylazine(3.2),and atrazine(2.6).For the atrazine metabolites investigated,the RP-HPLC-derived log K_(ow)values are significantly less than those directly measured(1.0 for desethylatrazine and 1.5 for desisopropylatrazine).In contrast to these findings,considerably higher log K_(ow)values were obtained for the two acid amides propachlor and metazachlor with both RP-HPLC methods compared to the shake-flask values(2.2 for both compounds).Because of the still complicated choice of reliable reference compounds/data for the RP-HPLC methods,the shake-flask technique should be preferred for determination of octanol/water partition coefficients with high accuracy in the range of log K_(ow)< 4.Finally,the directly measured KOW values were compared with estimates obtained with two widely applied group-contribution methods(CLOGP and LOGKOW).