Optimization and validation of a green analytical method for determining bixlozone herbicide in water

Bixlozone is a selective, persistent, and toxic isoxazolidinone herbicide recently authorized in Brazil for multiple crops. However, no extraction technique is currently available to monitor this molecule in the environment due to its recent introduction to the global pesticide market. Therefore, the objective of this study was to optimize and validate headspace solid-phase microextraction (HS-SPME) followed by analysis by gas chromatography coupled to mass spectrometry (GC-MS) to determine this compound in water. The results obtained revealed that the most suitable extraction conditions were achieved using polydimethylsiloxane (PDMS) fiber in which the water sample had its pH adjusted to 6, along with the addition of 10% (w/v) sodium sulfate, temperature maintained at 60 °C and an extraction time of 50 min. The detection and quantification limits achieved under these conditions were 0.12 and 0.4 μg L^-1, respectively. The linearity range was 0.4 to 16 μg L^-1 (r² = 0.9991), where the accuracy varied from 93% to 103% and the relative standard was lower than 15.7, confirming the technique's precision. The study of stability in water revealed a half-life between 56 and 66 days, in the presence and absence of light, respectively. Application of this technique to real water samples from different regions of Brazil has not yet detected residues of this herbicide. This technique scored 90 points on the analytical eco-scale, which means it is classified as an excellent environmental analysis protocol.