EVALUATION OF THE MOBILITY OF C-14-LABELED PESTICIDES IN SOILS BY THIN-LAYER CHROMATOGRAPHY USING A LINEAR ANALYZER

The mobility of seven pesticides in a chromic cambisol soil was studie d by soil thin layer chromatography. Pesticide mobilities were determi ned by means of conventional autoradiographs of the chromatograms, as well as from sequential series of curves and images of the pesticide s pots provided by a linear analyser. The R, values obtained from the au toradiographs and those provided by the linear analyser were quite con sistent. Based on such values, pesticide mobility decreased in the fol lowing order: acephate > fluometuron > atrazine > ethofumesate, metola chlor > diazinon > glyphosate. According to the mobility scale propose d by Helling and Turner (1968), acephate is highly mobile; atrazine, f luometuron, ethofumesate and metolachlor are moderately mobile; diazin on is slightly mobile; and glyphosate is immobile. The images provided by the linear analyser allow to determine the R, values for the zones of maximum activity in the pesticide spots (R(f)(max)), as well as th e activities of different spot zones and those corresponding to R(f) a nd R(f)(max). The results obtained show the image analyser to provide more expeditious R(f) measurements from the chromatograms and open up new prospects for using soil TLC to investigate pesticide mobility.