研究目的
To develop a new method for determining trace levels of the organophosphorus pesticide parathion-methyl in water samples using dispersive liquid-liquid microextraction (DLLME) followed by gas chromatography with electron capture detection (GC/ECD), and to evaluate its application in the study of the UV-photodegradation process of parathion-methyl under different conditions of pH and temperature.
研究成果
The DLLME-GC/ECD method developed is effective for the extraction and quantification of parathion-methyl in water samples, with high extraction efficiency and enrichment factor. The method was successfully applied to study the UV-photodegradation of parathion-methyl, showing that degradation is favored in acidic conditions and at higher temperatures. The optimized process can reduce parathion-methyl residues to levels below the maximum permitted by Brazilian legislation.
研究不足
The study's limitations include the influence of interfering anions in drinking water on the photodegradation process, which may compete with the pesticide for radiation absorption, potentially affecting the efficiency of the degradation process.
1：Experimental Design and Method Selection:
The study employed a chemometric experimental design to optimize the DLLME-GC/ECD method for analyzing parathion-methyl residues and evaluating its UV-photodegradation. The method involved the use of DLLME for extraction and pre-concentration of parathion-methyl from water samples, followed by GC/ECD analysis.
2：Sample Selection and Data Sources:
Distilled and drinking water samples spiked with parathion-methyl were used. The samples were subjected to UV-photodegradation under different pH and temperature conditions.
3：List of Experimental Equipment and Materials:
Equipment included a gas chromatograph (Shimadzu GC 2014) with an electron capture detector, a UV-Visible spectrophotometer (Cintra C-20), and a UV radiation source (TUV Sylvania 15 W germicidal lamp). Materials included parathion-methyl, bifenthrin (internal standard), toluene (extraction solvent), and acetonitrile (dispersive solvent).
4：Experimental Procedures and Operational Workflow:
The DLLME procedure involved injecting a mixture of dispersive and extraction solvents into the water sample, vortexing, centrifuging, and analyzing the extract by GC/ECD. The UV-photodegradation experiments were conducted in a batch reactor under UV254nm radiation, with samples collected at intervals for analysis.
5：Data Analysis Methods:
The data were analyzed using the Statistica 12 software. The method's performance was evaluated based on extraction efficiency, enrichment factor, limits of detection and quantification, linearity, accuracy, and precision.
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