A new approach to determination of the herbicide 2-methyl-4-chlorophenoxyacetic acid in soil

Introduction. Due to the tightening of the hygienic indicator of permissible concentration in soil for herbicide based on phenoxyacetic acid derivative (MCPA) from 0.04 mg/kg to 0.003 mg/kg, it became necessary to optimize analytical approaches to its determination. The aim of the study is to develop a modern method for determining MCPA in soil using high-performance liquid chromatography with mass spectrometric detection (HPLC-MS/MS), simplifying the previous technique by changing sample preparation and excluding the process of substance derivatization before analysis. Materials and methods. Determination was conducted by tandem liquid mass spectrometry with triple quadrupole mass detector (HPLC-MS/MS) in multiple reaction monitoring mode, using electrospray ionization as an ion source. The substance was extracted from soil samples with sodium hydroxide solution followed by acidification with hydrochloric acid to pH 3. Further purification of the extract was carried out on a solid-phase extraction cartridge based on a copolymer of divinylbenzene and N-vinylpyrrolidone. Results. The method was validated on standard soil samples of three different soil types by means of additions “applied-found”. It was possible to set the level of the lower limit of MCPA quantification at 0.001 mg/kg (with a set MPC value of 0.003 mg/kg). Limitations. The development was carried out using standard soil samples of three types available to the laboratory. Conclusion. The developed method included in the Register of certified methods. The approach proposed in the method allows analyzing a larger number of samples in less time and can be used in monitoring studies of MCPA residues in soil. Fast and sensitive HPLC-MS/MS method allowed to significantly reduce the sample preparation time in comparison with other gas-liquid chromatography methods, excluding the stage of derivatization of the substance into methyl ether.