Optimization of the separation of triazines, metabolites and phenylurea herbicides in mixture by reversed phase capillary electrochromatography.

The separation of ten different phenylurea and triazine herbicides in mixture was optimised by reversed phase Capillary Electrochromatography by studying the effect of several physico-chemical parameters, such as the mobile phase buffer type, pH and concentration, the acetonitrile concentration and the separation capillary length. Two different buffer systems were investigated, namely ammonium MES and acetate buffers in the pH range 5-7. In MES mobile phases the triazines herbicides elution order and separation was strongly influenced by the pH. The separation of atrazine and metobromuron compounds was difficult to obtain and was only achieved using a column of 62 cm total length. The separation of all the compounds in mixture was obtained in 5 mM ammonium acetate mobile phase pH 6.0 containing 75% of acetonitrile. Under these conditions the method was linear in the range 2.5-50.0 ug/mL and exhibited a detection limit of 1.25 ug/mL. By slightly lowering the mobile phase acetonitrile content the co-separation of the ten herbicides with the atrazine N-dealkylated metabolites was also successfully achieved.