Employing Solid Phase Microextraction as Extraction Tool for Pesticide Residues in Traditional Medicinal Plants

Advances in sample preparation methods for pesticide residue analysis in medicinal plants: A focus on Nepal

Medicinal plant safety is a rising challenge worldwide due to the continued overuse of pesticides to their maximum residue limits. Due to the high demand for medicinal plants, their production is being increased and sometimes protected by pesticide use. The analysis of these residues requires robust analytical methods to ensure the safety and quality of medicinal plants. Developing effective sample preparation for detecting pesticides is challenging, due to their diverse natures, classes, and physico-chemical characteristics. Hence, existing techniques and strategies are needed to improve the reliability of the results. The review discusses the current state of sample preparation techniques, analytical methods, and instrumental technologies employed in pesticide residue analysis in medicinal plants. It highlights the challenges, limitations, and advancements in the field, providing insights into the analytical strategies used to detect and quantify pesticide residues. Reliable, accessible, affordable, and high-resolution analytical procedures are essential to ensure that pesticide levels in medicinal plants are effectively regulated. By understanding the complexities of pesticide residue analysis in medicinal plants, this review article aims to support the conservation of medicinal plant resources, promote public health, and contribute to the development of sustainable strategies for ensuring the safety and quality of medicinal plants in Nepal. The findings of this review will benefit researchers, policymakers, and stakeholders involved in the conservation of medicinal plant resources and the promotion of public health.

Pesticide residues in herbs and their transfer for infusions

In this work, a cost-effective gas chromatography-mass spectrometry method was validated for the analysis of twenty-five pesticide residues in herbs and infusions using a quick, easy, cheap, effective, rugged, and safe procedure or a dispersive liquid-liquid microextraction method, respectively. Figures of merit of the method showed good accordance with current guidelines. From the 58 herb samples studied (pertaining to 20 different species), 80% presented at least one detectable pesticide, with 62% of them above the maximum residual level. Results showed that pesticide residues from naturally contaminated herbs were not transferred at a significant rate to the herbal infusions. When a control assay was conducted by spiking a blank herb sample with a large amount of each pesticide (7 mg/L) 15 analytes were detected below the limit of quantification in the infusion.

Pesticide residues in fruits and vegetables from the southern part of Botswana

This study reports a surveillance of multi-pesticide residues of fruits and vegetables sold in the local markets carried out in 2018-2019 in Botswana to access consumer safety. A validated method for analysis of 232 pesticide residues in fruits and vegetables was applied, based on QuEChERS-GC-MS/MS methodology. A total of 83 fruit and vegetable sold in different markets were bought from three different areas of the southern region . Levels of pesticides ranged between 0.0032 ± 0.0009 mg/kg and 70.4 ± 19.4 mg/kg. A total of 78% of the samples contained pesticide residues, whereas only 13% of the samples violated the EU/Codex MRLs. In particular, rape vegetable samples exceeded legislative limits most, followed by cabbage, green pepper and tomato. The most frequently detected compounds were chlopyrifos, chlorfenapyr, tebuconazole, methamidophos and cypermethrin. These results will serve as a foundation for future studies, involving continuous monitoring programmes.

Binary Dispersive Liquid-Liquid Microextraction Strategy for Accurate and Precise Determination of Micropollutants in Lake, Well and Wastewater Matrices

In this study, a binary mixture in dispersive liquid-liquid microextraction was used for the preconcentration and determination of selected pesticides, pharmaceutical and hormone by GC-MS. A Box-Behnken experimental design was used to optimize the amounts of binary mixture, dispersive solvent and salt. The optimum parameters obtained were dichloromethane/1,2-dichloroethane binary mixture (200 µL), ethanol (2.0 mL) and potassium nitrate (1.0 g). Analytical performance of each analyte was determined under the optimum conditions and the lowest and highest detection limits calculated were 0.43 and 5.9 ng/mL. Low relative standard deviations were obtained even in the lowest concentrations in linear calibration plots, signifying high precision for the sample preparation procedure and instrumental measurement. Accuracy of the developed method and applicability to real samples was tested on well, lake, hospital and municipal wastewater. The percent recoveries acquired at different spiked concentrations were satisfactory (89%-108%), validating the accuracy of the method for the quantification of the analytes in the selected matrices.

Accurate and Sensitive Determination Method for Procymidone and Chlorflurenol in Municipal Wastewater, Medical Wastewater and Irrigation Canal Water by GC-MS After Vortex Assisted Switchable Solvent Liquid Phase Microextraction

In this study, the detection power of a gas chromatography mass spectrometer (GC-MS) for procymidone and chlorflurenol was significantly enhanced using switchable solvent liquid phase microextraction (SS-LPME) as a preconcentration tool. This was achieved by a comprehensive optimization of significant parameters to the SS-LPME method such as switchable solvent amount, concentration and amount of sodium hydroxide, pH effect and mixing effect. The optimum experimental conditions obtained were used to determine analytical figures of merit for the analytes. The limits of detection obtained were 0.44 and 2.9 ng/mL for procymidone and chlorflurenol, respectively. The optimum method was applied to water sampled from an irrigation canal and two wastewater samples. The samples were spiked at two concentrations and the percent recovery results obtained ranged between 86 and 115% for both analytes. The recovery results together with the low standard deviations recorded validated the method as accurate and precise.

Simultaneous determination of iprodione, procymidone, and chlorflurenol in lake water and wastewater matrices by GC-MS after multivariate optimization of binary dispersive liquid-liquid microextraction

This study reports the optimization of a binary dispersive liquid-liquid microextraction method for the determination of iprodione, procymidone, and chlorflurenol by gas chromatography mass spectrometry. The study was aimed at using two extraction solvents to increase the extraction efficiency of all analytes. The binary solvents recorded results higher than the mono-solvents. After examining the effects of main experimental parameters and their interactions by analysis of variance, 200 μL of binary mixture (dichloromethane and 1,2-dichloroethane), 2.5 mL of ethanol, and 15 s vortex were obtained as optimum parameters. The detection and quantification limits calculated for the analytes were found to be between 0.30-1.6 and 1.0-5.3 ng/mL, respectively. Enhancement in detection power calculated as a ratio of the binary extraction detection limit to the detection limit of direct GC-MS analysis was 105-, 214-, and 233-fold for chlorflurenol, iprodione, and procymidone, respectively. In order to check the accuracy of the developed method, recovery study was performed. Water sampled from a lake and two wastewater samples from treatment facilities were spiked at two concentrations, and the percent recovery calculated for the samples ranged between 87 and 116%. These results confirmed the suitability of the method to real samples for accurate determination of the analytes at trace levels.

Accurate and sensitive determination of selected hormones, endocrine disruptors, and pesticides by gas chromatography-mass spectrometry after the multivariate optimization of switchable solvent liquid-phase microextraction

Switchable solvent liquid-phase microextraction was combined with gas chromatography and mass spectrometry to improve the sensitivity and accuracy for the determination of selected endocrine disruptors, pesticides, and hormones. The extraction method was used to complement gas chromatography with mass spectrometry by preconcentrating analytes for trace determinations. A Box-Behnken experimental design was used to evaluate the main variables and their interaction effects, and optimum parameters were selected based on the model of experimented results. Application of optimum extraction conditions to mixed standard solutions yielded limits of detection and quantitation values between 0.20-13 and 0.90-46 ng/mL, respectively. The accuracy and the applicability of the developed method was checked in tap water and two different wastewater samples by spiked recovery tests. The percent recoveries recorded for the analytes were between 91 and 110%, and percent relative standard deviation values were all below 10%. The results indicate that the method can be used for the accurate and sensitive determination of these analytes in the presented matrixes.