4-(p-Nitrobenzyl)pyridine as a spray reagent for the thin-layer chromatographic detection of dimethyl tetrachloroterphthalate herbicide.

The developed thin-layer chromatogram of DCPA (Dacthal) is sprayed with 4-(p-nitrobenzyl)pyridine chromogenic reagent followed by ammonium carbonate solution. The chromatogram is then heated in an over at 130 degrees C for 20 minutes. When cool, the chromatogram is sprayed with tetraethylenepentamine reagent. DCPA spots appear blue against a white background. The sensitivity of this test is about 1 microgram. The procedure is useful to detect DCPA in water and in soil.