Determination of Herbicides in Soil by Dispersive Solid-Phase Extraction, Dispersive Liquid–Liquid Microextraction, and High-Performance Liquid Chromatography

Current Research Status, Opportunities, and Future Challenges of Nine Representative Persistent Herbicides

Pesticides are extensively utilized in contemporary agriculture to manage pests, enhance crop yields, and sustain productivity. Nevertheless, the persistent herbicide represents a dual-edged weapon. On one hand, their prolonged efficacy enables reduced application frequency during crop growth seasons, resulting in cost savings on labor. However, the presence of these residues within fields poses safety risks to soil quality, sensitive crops in subsequent rotations, agricultural product quality, and the ecological environment. This review presents a comprehensive review on the mechanisms of action, application risks, ecotoxicology, and residue analysis methods of nine representative persistent herbicides (namely, atrazine, imazethapyr, imazapic, mesosulfuron-methyl, halosulfuron-methyl, fomesafen, diflufenican, quinclorac, and pyroxasulfone). The objective is to guide their scientific and rational utilization in agricultural practices while minimizing phytotoxicity risks and effectively monitoring and controlling soil pollution. These can not only provide practical recommendations for mitigating potential plant toxicity and ecological environmental risks but also contribute valuable technical insights for efficient soil pollution monitoring and prevention. Additionally, unaddressed research objectives were also anticipated.

Forensic profiling of non-volatile organic compounds in soil using ultra-performance liquid chromatography: a pilot study

Soil is of particular interest to the forensic community because it can be used as valuable associative evidence to link a suspect to a victim or a crime scene. Liquid chromatography is a powerful analytical tool for organic compound analysis. Recently, high-performance liquid chromatography (HPLC) has proven to be an efficient method for forensic soil analysis, especially in discriminating soils from proximity locations. However, ultra-performance liquid chromatography (UPLC), which is much more sensitive than HPLC, has never been explored in this context. This study proposed a UPLC method for profiling non-volatile organic compounds in three Malaysian soils (red, brown and yellowish-brown soils). The three soils were analysed separately to assess the effects of individual chromatographic parameters: (a) elution programme (isocratic vs. two gradient programmes); (b) flow rate (0.1 vs. 0.2 mL/min); (c) extraction solvent (acetonitrile vs. methanol) and (d) detection wavelength (230 vs. 254 nm). The injection volume and total run time were set to 5 µL and 35 min, respectively. Consequently, each soil sample gave 24 different chromatograms. Results showed that the most desirable chromatographic parameters were (a) isocratic elution; (b) flow rate at 0.2 mL/min and (c) acetonitrile extraction solvent. The proposed UPLC system is expected to be a feasible method for profiling non-volatile organic compounds in soil, and is more chemical-efficient than a comparable HPLC system.

Sensitive fluorometric determination of quinclorac residues in rice

Rice is one of the most important foods in the world due to its high nutritional value and production. Quinclorac, a selective herbicide, is one of the most detected pesticide residues in rice crops according to pesticide monitoring studies. Common methods for the determination of quinclorac in rice are very time-consuming and labour-intensive, so it is important to develop alternative sensitive and simple analytical methods able to detect quinclorac in food samples. Here we propose a fluorometric method for the screening of this herbicide at excitation/emission wavelengths of 238/358 nm/nm, respectively. A modified QuEChERS method was selected for sample treatment due to its simplicity and high recovery yields. The proposed method presents a detection limit of 2.5 ng mL^-1 and satisfactory precision. Recovery experiments were performed in different kinds of rice (white and brown) at or below the Maximum Residue Limit established in European Union (5 mg kg^-1), obtaining values close to 100%. All these characteristics ensure that the proposed method fulfils the requirements for its application in food control.

Synergistic effects between hydroxyl radicals and hydrated electrons on strengthening decomposition of an s-triazine compound: A combined experimental and theoretical study

The decomposition of an environmentally recalcitrant s-triazine compound, prometry (PMT), was carried out by experimental and theoretical approaches to study the combined effects of hydroxyl radicals (OH) and hydrated electrons (e_aq^-). With the participation of strongly oxidative radicals OH and reductive radicals e_aq^- induced by electron beam (EB), PMT obtained a good decomposition performance, which was obviously better than those methods simply using OH as the single active species. The evolution of cyanuric acid (CA) during the EB and UV irradiation processes elucidate that former method could efficiently decompose such chemically stable intermediate. The experiments of radical scavengers further suggest that OH was the predominant radical during PMT degradation, while e_aq^- was beneficial to further decomposition and mineralization. Combined with the results of density functional theory (DFT) calculations, the strengthened synergistic effects between OH and e_aq^- were proven. The calculations illustrated OH could attack the carbon-branch-chains of s-trazine ring and form OH-adducts rather than nitrogen oxides. Moreover, the presence of e_aq^- could not only greatly change the geometry of the s-triazine ring, but also help cleaving alkyl chain on ring, thus facilitate the complete mineralization.