Simple sensitive technique for detecting organochlorine pesticides on thin layer chromatograms

Chlorinated hydrocarbon pesticides can be quickly detected using commercially available thin layer chromatographic plates dipped in an acetone solution of silver nitrate. The limits of detection are functions of the pesticide, adsorbent, developing system, and concentration of the silver nitrate in acetone solution. On exposure to ultraviolet light, 0.002 microgram 2,4,5-T produced clear darkening within 30 min on precoated silica gel plates (polyvinyl alcohol binder) coated with a solution of 0.1% silver nitrate in acetone. For this system, a 60-min detection period was necessary for a 0.05% coating solution. On the silica gel plates (polyvinyl alcohol binder, 0.1% silver nitrate), 0.02 microgram lindane is detected within 75 min. For alumina plates (polyvinyl alcohol binder, 0.1% silver nitrate), 0.025 microgram aldrin is detected within 10 min. Darkening of this plate prohibits the detection of 0.012 microgram aldrin. On silica gel plates (polyvinyl alcohol binder, 0.1% silver nitrate), 0.015 microgram aldrin can be detected within 45 min. The method described provides sensitivities equal to or exceeding literature values.