Metodologias para determinação e avaliação da estabilidade do 2,4-D em amostras de água

Abstract

The 2,4-Dichlorophenoxyacetic acid (2,4-D) is widely used to weeds control in rice, coffee, sugar cane, eucalyptus, millet, corn, pasture, soy, wheat, among other crops. However, this pesticide may cause contamination of water resources, and generate environmental and public health problems. Therefore, it is desirable to develop new extraction methodologies for this compound in water samples. This study aimed to optimize and validate liquid-liquid extraction with low temperature partition (LLE-LTP) and Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) for determination and evaluation of 2,4-D stability in water samples by high performance liquid chromatography with diode array detector (HPLC-DAD). The recovery percentages of the two methodologies were close to 100±3%, and the limits of quantification (LOQ) were 2.00 and 3.10 µg L-1 for LLE-LTP and QuEChERS, respectively, being below the maximum residue limit established by Brazilian and international legislations. The methodologies were selective, precise, accurate, without matrix effect, and presented linearity from 2.00 - 26.0 and 3.10 - 40.6 μg L-1 for LLE-LTP and QuEChERS, respectively. Therefore, they represent accessible and efficient alternatives for monitoring 2,4-D in water samples. From the comparative analysis, we found that the LLE-LTP had less number of steps, less consumption of salts and sample and lower LOQ, compared to the QuEChERS method. The real samples did not reveal any environmental contamination episodes by 2,4-D. This result may be associated with the absence of 2,4-D in the samples, or concentration levels are below the LOQ. Furthermore, this herbicide may have been degraded in the samples, because we found that after 60 days, in environmental conditions, the concentration of 2,4-D in this matrix cannot be quantified by LLE-LTP coupled to HPLC-DAD.