Herbicide Dispersal Patterns: II. Mapping Residues Using X-ray Fluorescence

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Abstract
Distribution patterns of foliar applied herbicides can be studied by x-ray element mapping provided the herbicide contains an atom with an atomic number of 11 (sodium) or greater. The suitability of an herbicide for element mapping increases as the number of similar detectable atoms per molecule increases. Herbicides containing one detectable atom per molecule provide usable element maps at concentrations of 1.12 kg/ha and higher. Inaccurate element maps can result from: (1) Formulation components containing detectable atoms the same as those of the active ingredient. (2) Herbicide volatility during analysis due to reduced pressures and heating. (3) Specimen topography preventing x-ray detection at some locations on the plant surface. (4) Herbicide concentrations that are below the minimum detectable limit. If adequate precautions are followed in the use of x-ray element mapping, a wide range of uses exist in weed science.