A SCREENING METHOD FOR THE DETERMINATION OF THE RESIDUES OF URACIL HERBICIDES IN MELISSA-OFFICINALIS L

A screening analytical method has been worked out for the determination of the residues of uracil herbicides in Melissa officinalis L. The method is based on separation by TLC and quantitative evaluation using the selective biochemical detection of herbicides inhibiting the Hill reaction. The recovery of the method at the contamination level of 0.1 mg.kg(-1) was 81.2%, 85.5%, and 82.4% for bromacil, lenacil, and terbacil, respectively. At the contamination level of 0.01 mg.kg(-1), the recovery was close to 72%. The limit of detection is 0.1 ng of each herbicidal compound. Limit of quantitation of the method is 0.01 mg.kg(-1), limit of detection 0.005 mg.kg(-1). The screening TLC method is simple and rapid, enabling routine evaluation of medicinal plants for herbicide residues at the levels near the Maximum Residue Limit (MRL). In samples of Melissa officinalis L. (green plant) treated with the herbicidal formulation Sinbar(R), low levels of terbacil residues (0.005 to 0.01 mg.kg(-1)) have been found.