Simultaneous determination of captan and captafol in apples and potatoes by thin layer chromatography and in situ fluorometry.

A simple method is described for the simultaneous quantitative determination of captan [N-(trichloromethylthio)-3a,4,7,7a-tetrahydrophthalimide] and captafol [N-(1,1,2,2-tetrachloroethylthio) -3a,4,7,7a - tetrahydrophthalimide] in apples and potatoes. The fungicide residues are extracted with acetonitrile, partitioned into a solution of methylene chloride in petroleum ether, separated from each other and the co-extractives on a thin layer chromatographic plate impregnated with aluminum chloride, sprayed with sodium chlorate, and heated. The fluorescence is then measured directly from the chromatogram. Recoveries were greater than 90% in the test crops at the 0.2 ppm level.