Thin Layer Chromatography with Automated Multiple Development (AMD-TLC)

Abstract

AMD (Automated Multiple Development) is a thin layer chromatographic technique, which combines the wide range of polarity gradient elution on silica with a separation power similar to HPLC. By AMD it is possible to analyze in parallel twelve samples of ground or drinking water simultaneously for some dozens of pesticides within one run. The active ingredients are enriched by solid phase extraction. The limit of the practical working range is 0.05 μg active ingredient per liter. The first step of the AMD analysis consists of a screening for the active ingredients of interest by gradient elution on silica plates, UV multidetection and in situ derivatization of not UV active compounds. The second step confirms positive results by an AMD separation in a gradient with a totally different chromatographic selectivity and by taking the UV spectras of sample and standard. By the combination of both steps, all the active ingredients of pesticides on the market are clearly differentiated. With adequate cleanliness, off-line coupling of AMD and mass spectroscopy permits confirmation of relevant results by direct inlet. In several collaborative studies for the determination of pesticides in water, AMD was compared with all the other more common techniques. The results of the AMD multimethod proved to be at least as valid as the results of the common methods. The standardization of AMD as a DIN method 38407-part 11 for the determination of pesticides in ground and drinking water was finished in 1993.