An in-line clean-up and extraction method for 2,4-dichlorophenol, atrazine, and metribuzin in high-adsorbent matrices: Soil and polymeric resin samples

Abstract

In this study, an extraction method was developed, incorporating in-situ sample clean-up and efficient recovery of liquid extracts from high-adsorbent matrices as soil and polymeric resin. The method was based on Ultrasonic Assisted Extraction employing a coupled double tube, with a silica gel disk for interference removal. Subsequent extract recovery was achieved through centrifugation. Optimization of the method was accomplished using a mixed 2- and 3-level factorial experimental design, guided by desirability center on the recovery of four prevalent herbicides (2,4-dichlorophenol, desethylatrazine, Atrazine, and Metribuzin). Under the identified optimal conditions, the method exhibited reduced solvent usage, energy consumption and time requirement in comparison to the reference Soxhlet extraction method. Conducting three consecutive 5-minute extractions utilizing acetone (0.5 mL for soil or 5.0 mL for resin) as the solvent, along with 0.25 g of compacted silica gel for clean-up, yielded recoveries between 84.9 ± 3.1% and 95.2 ± 7.7%. Matrix effect was significant for both soil and resin samples, for soil a signal enhancement up to 12.2% was observed, meanwhile for resin the signals were depleted up to 16.9%. Method calibration curves were employed to account for matrix effect in real samples. Method detection limits ranged from 0.3 to 1.1 ng g−1 for soil samples and from 16.1 to 18.0 ng g−1 for resin samples. The intra- and inter-day precision (RSD) remained under 7.5% for resin samples and below 5.0% for soil samples. Accuracy (bias) values were below 4.4 ± 0.5% and 7.8 ± 1.1% for resin and soil samples, respectively. Application of the method to real samples collected from a potato crop in southern Mexico City revealed herbicides concentrations ranging from 0.02 to 2.94 µg g−1 in soil samples and from 79.7 to 103.3 ng g−1 in resin samples obtained from air sampling.