Abstract
The aim of this study was the modification and application of the QuEChERS method for the preparation and purification of samples in order to determine the level of captan in real wastewater originating from a plant protection products factory which was characterized by a significant content of organic substances [Chemical Oxygen Demand (COD) = 856 ± 128 mg O2/L and Total Organic Carbon (TOC) = 62 ± 9 mg/L]. The optimization of the method consisted of the selection of solvents used for the extraction of captan from wastewater and also sorbents used to purify the extracts by the dispersion of a solid phase extraction technique (dSPE). Two steps were used: extraction and clean-up. In the extraction step, acetonitrile was replaced by anacetonitrile:acetone mixture. In the clean-up step by the dSPE, five sorbents were tested: Florisil®, aluminum oxide (Al2O3), zirconium oxide (ZrO2), silicon oxide (SiO2) and PSA (primary and secondary amine). Concentrations of captan in wastewater extracts were determined by gas chromatography (GC) combined with electron capture detection (μECD). The best recovery parameters and precision of the method were obtained for samples purified using ZrO2 (recovery 98% and precision expressed as relative standard deviation RSD 8%) and Florisil® (recovery 96%, RSD 9%). Limits of detection (LOD) and quantification (LOQ) for determination of captan in diluted extract of wastewater were 0.003 and 0.01 mg/L, respectively. Matrix effects were in the range of −69% to −44% for samples purified by ZrO2 and Florisil®, respectively. The modified and optimized method was applied for fast and simple determination of captan levels in real industrial wastewater samples, in which the concentration of captan in diluted extract was determined to be 4.0 ± 0.3 mg/L.
Highlights
Plant protection products are a mixture of various substances, i.e., active substances used to control pests, diseases and weeds, adjuvants which improve adhesion to plants and numerous functional additives with emulsifying, wetting, anti-freezing, anti-scaling, dispersing or anti-foaming properties [1,2]
Matrix effects were in the range of −69% to −44% for samples purified by ZrO2 and Florisil®, respectively
The wastewater originating from the same plant protection products factory was analysed for selected physicochemical parameters
Summary
Plant protection products are a mixture of various substances, i.e., active substances used to control pests, diseases and weeds, adjuvants which improve adhesion to plants and numerous functional additives with emulsifying, wetting, anti-freezing, anti-scaling, dispersing or anti-foaming properties [1,2]. These substances are responsible for ensuring the appropriate application properties of products. As a result of their use in technological processes, these substances contaminate the wastewater, significantly determining their composition and physicochemical properties even though they often have a negative impact on the efficiency of treatment processes used in factory sewage treatment plants. In Poland, for instance, there are 34 plant protection products which contain captan [5], produced in the form of powders, granules, or concentrates for dissolving in water
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