Determining pyroxasulfone herbicide in honey samples using liquid-liquid extraction with low temperature purification (LLE-LTP)

Pyroxasulfone is a selective, systemic, pre-emergence herbicide which acts to inhibit weeds in potato, coffee, sugar cane, eucalyptus, and soybean plantations, among others. This active ingredient was classified by Brazilian legislation as a very dangerous product for the environment, and to date there are no studies involving the development of extraction methods for monitoring this compound in environmental matrices. Therefore, the objective of this study was to optimize and validate liquid-liquid extraction with low temperature purification followed by a gas chromatography coupled to mass spectrometry analysis to determine this herbicide in honey samples. The results showed that the best extractor phase was acetonitrile and ethyl acetate (6.5 mL:1.5 mL), with recovery rates close to 100% and relative standard deviations below 11%. The validation proved that the extraction method was selective, precise, accurate and linear in the range of 3-225 μg kg-1, reaching a limit of quantification of 3 μg kg-1, with a -25.95% matrix effect. Monitoring on real samples did not reveal episodes of environmental contamination with pyroxasulfone residue.

Optimization and validation of LLE-LTP to determine florpyrauxifen-benzyl herbicide in water samples by HPLC-DAD

Florpyrauxifen-benzyl is a systemic herbicide which acts on weeds of common occurrence in rice cultivation areas using flooded or rainfed systems. The Brazilian Health Regulatory Agency (ANVISA) authorized the commercialization of this pesticide, but did not establish guidelines with an extraction and quantification method of residues of this compound as a form of environmental monitoring. Therefore, the present study aimed to optimize and validate the liquid-liquid extraction with low temperature purification (LLE-LTP) to determine florpyrauxifen-benzyl content in water samples by high performance liquid chromatography with diode array detection (HPLC-DAD). The recovery ranged from 95.84 to 105.4% with a relative standard deviation less than 1.5. LLE-LTP was selective, precise, accurate, linear in the range from 4.00 to 150 µg L^-1, and the limit of quantification was 4.00 µg L^-1. The stability study of the compound in water revealed its degradation in 25 days and DT₅₀ in approximately 5 days. LLE-LTP coupled to HPLC-DAD presented itself as a simple, easy and efficient method of extracting and analyzing it in water samples.