Dispersive Liquid-Liquid Microextraction Combined with Gas Chromatography-Mass Spectrometry for the Determination of Multiple Pesticides in Celery

Solvent-Focused Gas Chromatographic Determination of Thymol and Carvacrol Using Ultrasound-Assisted Dispersive Liquid-Liquid Microextraction through Solidifying Floating Organic Droplets (USA-DLLME-SFO)

An ultrasound-assisted dispersive liquid-liquid microextraction by solidifying floating organic droplets, coupled to a form of temperature-programmed gas chromatography flame ionization detection, has been developed for the extraction and determination of thymol and carvacrol. This method utilizes undecanol as the extraction solvent, offering advantages such as facilitating phase transfer through solidification and enhancing solvent-focusing efficiency. The optimal gas chromatography conditions include a sample injection volume of 0.2 µL, a split ratio of 1:10, and a flow rate of 0.7 mL min-1. The extraction conditions entail an extraction solvent volume of 20 µL, a disperser solvent (acetone) volume of 500 µL, pH 7.0, 7.0% NaCl (3.5 M), a sample volume of 5.0 mL, an ultrasound duration of 10 min, and a centrifuge time of 7.5 min (800 rpm). These conditions enable the achievement of a high and reasonable linear range of 3.5 to 70. 0 μg mL-1 for both thymol and carvacrol. The detection limits are found to be 0.95 and 0.89 μg mL-1, respectively, for thymol and carvacrol. The obtained relative standard deviations, 2.7% for thymol and 2.6% for carvacrol, demonstrate acceptable precision for the purpose of quantitative analysis.

Rapid and reliable detection and quantification of organophosphorus pesticides using SERS combined with dispersive liquid-liquid microextraction

Rapid and reliable detection and quantification of pesticide residues in complex matrices by surface enhanced Raman spectroscopy (SERS) remain challenging due to the low level of target molecules and the interference of nontarget components. In this study, SERS was combined with dispersive liquid-liquid microextraction (DLLME) to develop a rapid and reliable method for the detection of organophosphorus pesticides (OPPs). In this method, DLLME was used to extract and enrich two representative OPPs (triazophos and parathion-methyl) from a liquid sample, and a portable Raman spectrometer was used to analyze the separated sediment using homemade gold nanoparticles colloids as enhancing substrates. The results showed that the developed method displayed good sensitivity and stability for the detection and quantification of triazophos and parathion-methyl with R² ≥ 0.98. The calculated limits of detection (LODs) in the simultaneous detection of triazophos and parathion-methyl were 2.17 × 10^-9 M (0.679 ppb) and 2.28 × 10^-8 M (5.998 ppb), and the calculated limits of quantification (LOQs) were 7.23 × 10^-9 M (2.26 ppb) and 7.62 × 10^-8 M (19.098 ppb), respectively. Furthermore, the developed SERS method was successfully applied to the detection of triazophos and parathion-methyl in apple juice with recoveries between 78.07% and 110.87% and relative standard deviations (RSDs) ≤ 2.06%. Therefore, the developed DLLME facilitated liquid SERS method exhibited good sensitivity and stability for the rapid detection and quantification of OPPs and had the potential to be applied to the rapid detection of OPPs in complex matrices.

Dispersive liquid-liquid microextraction coupled with microfluidic paper-based analytical device for the determination of organophosphate and carbamate pesticides in the water sample

A microfluidic paper-based analytical device (µ-PAD) is a promising new technology platform for the development of extremely low-cost sensing devices. However, it has low sensitivity that might not enable to measure maximum allowable concentration of various pollutants in the environment. In this study, a dispersive liquid-liquid microextraction (DLLME) was developed as a preconcentration method to enhance the sensitivity of the µ-PAD for trace analysis of selected pesticides. Four critical parameters (volume of n-hexane and acetone, extraction time, NaCl amount) that affect the efficiency of DLLME have been optimized using response surface methodology. An acceptable mean recovery of 79-97% and 83-93% was observed at 1 µg L^-1 and 5 µg L^-1 fortification level, respectively, with very good repeatability (2.2-6.01% RSD) and reproducibility (5.60-10.41% RSD). Very high enrichment factors ranging from 317 to 1471 were obtained. The limits of detection for the studied analytes were in the range of 0.18-0.41 µg L^-1 which is much lower than the WHO limits of 5-50 µg L^-1 for similar category of analytes. Therefore, by coupling DLLME with µ-PAD, a sensitivity that allows to detect environmental threat and also that surpassed most of the previous reports have been achieved in this study. This implies that the preconcentration step has a paramount contribution to address the sensitivity problem associated with µ-PAD.

Residue and Risk Assessment of Imidacloprid and Chlorantraniliprole in Open Field and Greenhouse Celery

ABSTRACT

The residue levels and risk assessment of imidacloprid (IMI) and chlorantraniliprole (CAP) in celery grown under open field and greenhouse cultivation were investigated. Both pesticides were used through foliar application and soil drench application at the recommended dose (RD) and 10-fold recommended dose (10RD). The half-lives of IMI and CAP in celery were 1.9 to 5.8 days and 4.3 to 6.5 days after foliar application, respectively, and the dietary risk quotients of IMI and CAP were 14.8 to 18.3% and 1.0 to 1.2%, respectively. For soil drench application, the half-lives of IMI and CAP in soil were 17.5 to 28.5 days and 15.1 to 23.7 days, respectively. Celery plants were able to absorb both insecticides from the soil. The highest concentrations of IMI in celery plants were 0.12 to 0.24 mg kg-1 (RD) and 0.34 to 0.39 mg kg-1 (10RD), and those for CAP were 0.0081 to 0.015 mg kg-1 (RD) and 0.028 to 0.057 mg kg-1 (10RD). Based on the highest residues of IMI and CAP in celery, the dietary risk quotients of IMI and CAP were 15.0% (RD) to 15.6% (10RD) and 1.0% (RD and 10RD) after soil drench application, respectively. The observed bioconcentration factors were 1.38 to 2.11 (IMI) and 0.35 to 0.48 (CAP), indicating that celery accumulated IMI more easily than CAP. The foliar and soil applications of IMI and CAP in celery at the RD and 10RD do not pose a safety risk to consumers.

HIGHLIGHTS

Analysis of Degradation Kinetics and Migration Pattern of Chlorfenapyr in Celery (Apium graveliens L.) and Soil Under Greenhouse Conditions at Different Elevations

The degradation kinetics and migration pattern of chlorfenapyr in celery and soil at Lhasa and Pengzhou were investigated. A simple, rapid analytical method for the quantification of chlorfenapyr in celery and soil was developed using gas chromatography-tandem mass spectrometer. The results indicated that the half-lives of chlorfenapyr in celeries and soils at Lhasa were 6.3 days and 12.8 days. While the half-lives of chlorfenapyr in celeries and soils at Pengzhou were 6.9 days and 20.4 days. The half-lives of chlorfenapyr in celeries and soils at Lhasa were shorter than that at Pengzhou, while the half-lives of chlorfenapyr in soils at Lhasa and Pengzhou were longer than that in celeries at Lhasa and Pengzhou. The final residues of chlorfenapyr in celeries at Lhasa and Pengzhou were 5.074 ± 0.144 mg/kg and 5.981 ± 0.234 mg/kg after 7 days of spraying, respectively. When chlofenapyr was sprayed to soils only, the average root concentration factor of chlorfenapyr were 3.57-4.02, while the average translocation factor of chlorfenapyr in leaves and stems were 0.28-0.38 and 0.20-0.25, respectively. Chlorfenapyr was easy to migrate from soil to the roots of celery, followed by leaves and stems. The limit value of chlorfenapyr in celery has not been specified in China's National MRL standard (GB 2763 in National food safety standard-maximum residue limits for pesticides in food. Standard, Beijing, 2021), this study was useful to draw up the limit values of chlorfenapyr residues in celery at different elevations.

Highly selective monoclonal antibody-based lateral flow immunoassay for visual and sensitive determination of conazole fungicides propiconazole in vegetables

The conazole fungicide propiconazole is frequently found in vegetables although usage is not allowed. To overcome the high-cost and time-consuming labour requirements of instrumental methods, we developed a simple and visual lateral flow immunoassay for the sensitive determination of propiconazole. A hapten was carefully designed to raise a monoclonal antibody against propiconazole. Bal b/c mice were immunised with the hapten-carrier protein conjugate and a specific monoclonal antibody (mAb) was produced. Based on this mAb, a sensitive immunochromatographic strip assay (ICA) was established for rapid screening of propiconazole in vegetable samples. After optimisation of analytical parameters, the ICA strip showed a detection limit of 0.13 ng g-1 and a linear range from 0.5 to 80 ng g-1 using a strip reader. The assay also can be read by the naked eye with a visual limit of detection of 80 ng g-1. The recoveries for spiked vegetable samples by ICA ranged from 85.2% to 114.9%, with a coefficient of variation less than 11.7%. The assay time is within 45 min for a single sample including the sample pre-treatment. For spiked and blind samples, the detection capability of ICA was equivalent to liquid chromatography-mass spectrometry.

Determination of Organochlorine Pesticides in Green Leafy Vegetable Samples via Fe3O4 Magnetic Nanoparticles Modified QuEChERS Integrated to Dispersive Liquid-Liquid Microextraction Coupled with Gas Chromatography-Mass Spectrometry

A fast method based on Fe₃O₄ magnetic nanoparticles (Fe₃O₄ MNPs) modified QuEChERS integrated to dispersive liquid-liquid microextraction (DLLME) coupled with gas chromatography-mass spectrometry was established for the determination of 8 organochlorine pesticides (OCPs) in green leafy vegetables. The factors involved in the purification by QuEChERS and concentration by DLLME were optimized. In the QuEChERS process, Fe₃O₄ MNPs were used as a new impurity adsorbent after the sample extraction procedure by acetonitrile, which achieved phase separation rapidly. Carbon black was used as an alternative to costly graphitized carbon black without affecting the recovery. In the process of DLLME, 1 mL of the extract obtained by QuEChERS was used as the dispersive solvent, 40 μL of chloroform was used as the extractive solvent, and 4 mL of water was added. Making them mix well, then the dispersed liquid-liquid microextraction concentration was subsequently carried out. The enrichment factors of 8 OCPs ranged from 22.8 to 36.6. The recoveries of the proposed method ranged from 78.6% to 107.7%, and the relative standard deviations were not more than 7.5%. The limits of detection and limits of quantification were 0.15-0.32 μg/kg and 0.45-0.96 μg/kg, respectively. The method has been successfully applied to the determination of OCPs in green leafy vegetable samples.

Optimized Vortex-Assisted Dispersive Liquid–Liquid Microextraction Coupled with Spectrofluorimetry for Determination of Aspirin in Human Urine: Response Surface Methodology

Background:

A Vortex-assisted dispersive liquid-liquid microextraction (VA-DLLME) method is presented for the determination of aspirin (acetylsalicylic acid) in human urine by spectrofluorimetry.

Objective:

To determine trace levels of aspirin in biologic samples by using green and low-cost method development.

Methods:

For the microextraction procedure, chloroform and acetonitrile were used as extraction and disperser solvent, respectively. The factors affecting the efficiency of extraction such as volume of chloroform, volumes of acetonitrile, ionic strength, sample pH, centrifuging time, and extraction time were investigated. Then significant variables were optimized by the response surface method using the Box- Behnken design.

Results:

Under the optimum extraction conditions, a linear calibration curve in the range of 0.1 to 130 ng mL-1 with a correlation coefficient of R2 = 0.998 was obtained. The limits of detection (LOD) and limits of quantification (LOQ) were 0.031 and 0.103 ng mL-1, respectively. The relative standard deviations (RSD) were less than 4%.

Conclusion:

Enrichment factor and recoveries were achieved for the extraction of aspirin in human urine. This method gives a rapid, simple, sensitive and environmentally friendly for the measurement of trace amount aspirin.

Development and evaluation of an automated multi-channel multiplug filtration cleanup device for pesticide residue analysis on mulberry leaves and processed tea

An automated multi-channel multiplug filtration cleanup (m-PFC) device was designed and developed. m-PFC columns were suitably installed in the device. The cycle times, speed and nitrogen pressure parameters of the m-PFC column were optimized. The device was utilized to analyze the 82 pesticide residues in fresh mulberry leaves and processed tea with GC-MS/MS detection. Method validation was performed on 82 pesticide residues in fresh mulberry leaves and processed tea at spiked levels of 0.01, 0.05 and 0.5 mg kg⁻¹. The fortified recoveries of 82 pesticides were 72–115% and the relative standard deviations were 1–15%, except for diniconazole and clodinafop-propargyl in mulberry leaves. The automated multi-channel m-PFC device was successfully applied to detect the pesticide residues in fresh mulberry leaves and processed tea samples. With comparison to the conventional QuEChERS method, the current method using this device did not need additional vortex or centrifugation steps, and could process 48–64 samples in about one hour. The automated m-PFC method saved labor and improved the precision and was shown to be efficient and practical in pesticide residue analysis.

An automated device based on QuEChERS cleanup was developed, which is simple, fully automated, highly precise and highly efficient.

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 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.