Comparison of soxhlet and microwave-assisted extractions efficiency for the determination of herbicides in soil and maize crop: Cumulative and health risks assessment

The effectiveness of microwave-assisted extraction (MAE) and Soxhlet extraction (SE) was compared for the determination of herbicides (atrazine, 2.4 dichlorophenoxyacetic acid, mesotrione, and glyphosate) in soil and maize crop followed by gas chromatography with flame ionization detector. The recoveries of herbicides in maize and soil were 62%-80% and 70%-81%, respectively, for SE, whereas they were 80%-98% and 85%-101%, respectively, for MAE. The analysis repeatability, represented as relative standard deviations were <20% for all herbicides in both methods. All the herbicides calibration curves showed a good correlation coefficient (R-2) >= 0.996, indicating good linearity. The SE limits of detection and quantification ranged between 0.22 and 0.32 <mu>g L-1, and between 2.2 and 3.2 mu g L-1, respectively, whereas they were between 0.1 and 0.29 mu g L-1, and between 1.0 and 2.9 mu g L-1, respectively for MAE. These findings showed that MAE method is more accurate and sensitive than SE, thus can be accurately applied for the determination of the assessed herbicides in soil and maize cop. Herbicides concentrations obtained ranged from 2.7 to 20.4 mu g L-1 in maize and from 1.2 to 30.5 mu g L-1 in soil samples. The concentrations obtained in maize were higher than the maximum residue limits suggesting that health effect may occur upon continuous consumption. The herbicides toxicity index further confirmed the possible high toxicity effect of the studied maize crop as it exceeded the threshold value of 1. However, the health risk index was lower than 100% limit and did not exceed the acceptable daily intake of the maize crop in both adult and children indicating no health effect.