Investigation of Selected Sulfonylurea Herbicides by TLC and HPLC

Abstract

The following selected sulfonylurea herbicides have been investigated: thifensulfuron methyl (10), triasulfuron (11), chlorsulfuron (12), rimsulfuron (13), amidosulfuron (14), and tribenuron methyl (15) by NP‐TLC, RP‐TLC, and RP‐HPLC. The best separations of sulfonylurea herbicides were obtained by NP‐TLC (on silica gel and benzene‐methanol mobile phase in volume composition 90:10), but the technique did not enable complete separation of all compounds, chlorsulfuron was not separated from thifensulfuron methyl. This pair can be separated by RP‐TLC and use of a mobile phase with an organic mixture (acetonitrile‐methanol, 1:1, v/v) ‐ 0.1% H3PO4 in the volume composition 70:30. The separation of all investigated herbicides is not possible in applied chromatographic RP‐TLC conditions. The retention times (t R), the peak resolutions (R S), and the separation factors (α) obtained by RP‐HPLC indicate that the mobile phases acetonitrile – methanol – 0.1% H3PO4 in volume compositions 25:25:50, as well as 30:20:50 are the best for separations of this group of herbicides. Degradation of sulfonylurea herbicides happened in the range of 75–100% after 168 h. This fact permits accepting investigated pesticides as an unstable class of compounds (degradation after 1–12 weeks) in a water environment. From among investigated herbicides, the weakest stability in a water environment involved rimsulfuron and tribenuron methyl. Their concentration after 24 h was below 1% of initial concentration.