Sensitive Detection of Organophosphorus Pesticides in Medicinal Plants Using Ultrasound-Assisted Dispersive Liquid-Liquid Microextraction Combined with Sweeping Micellar Electrokinetic Chromatography

Nanozyme as detector and remediator to environmental pollutants: between current situation and future prospective

The term "nanozyme" refers to a nanomaterial possessing enzymatic capabilities, and in recent years, the field of nanozymes has experienced rapid advancement. Nanozymes offer distinct advantages over natural enzymes, including ease of production, cost-effectiveness, prolonged storage capabilities, and exceptional environmental stability. In this review, we provide a concise overview of various common applications of nanozymes, encompassing the detection and removal of pollutants such as pathogens, toxic ions, pesticides, phenols, organic contaminants, air pollution, and antibiotic residues. Furthermore, our focus is directed towards the potential challenges and future developments within the realm of nanozymes. The burgeoning applications of nanozymes in bioscience and technology have kindled significant interest in research in this domain, and it is anticipated that nanozymes will soon become a topic of explosive discussion.

A two-step strategy for simultaneous dual-mode detection of methyl-paraoxon and Ni (Ⅱ)

Exogenous pollution of Chinese medicinal materials by pesticide residues and heavy metal ions has attracted great attention. Relying on the rapid development of nanotechnology and multidisciplinary fields, fluorescent techniques have been widely applied in contaminant detection and pollution monitoring due to their advantages of simple preparation, low cost, high throughput and others. Most importantly, synchronous detection of multi-targets has always been pursued as one of the major goals in the design of fluorescent probes. Herein, we firstly develop a simultaneous sensing method for methyl-paraoxon (MP) and Nickel ion (Ni, Ⅱ) by using carbon based fluorescent nanocomposite with ratiometric signal readout and nanozyme. Notably, the designed system showed excellent effectiveness even when the two pollutants co-exist. Under the optimum conditions, this method provides low limits of detection of 1.25 µM for methyl-paraoxon and 0.01 µM for Ni (Ⅱ). To further verify the reliability, recovery studies of these two analytes were performed on ginseng radix et rhizoma, nelumbinis semen, and water samples. In addition, smartphone-based visual analysis has been introduced to expand its applicability in point of care detection. This work not only expands the application of the dual-mode approach to pollutant detection, but also provides insights into the analysis of multiple pollutants in a single assay.

High efficient solid-phase microextraction based on a covalent organic framework for determination of trifluralin and chlorpyrifos in water and food samples by GC-CD-IMS

Novel porous covalent organic framework (COF) based on condensation reaction between cyanuric chloride, 4,4'-ethylendianiline, and 3,4,9,10-perylenetetracarboxylic dianhydride was synthesized via sealed tube condition. The results COF was used as a new adsorbent for solid-phase microextraction (SPME) for extracting trifluralin and chlorpyrifos from vegetables, fruit samples, and wastewater. Gas chromatograph with a corona discharge-ion mobility spectrometer as the detector was also used for analyzing the target analytes. Some parameters that affected the extraction, such as stirring rate, time and temperature of extraction and pH were investigated, exhaustively. The detection limits were 0.13, and 0.15 µg/L and the linear ranges of 0.45-20 and 0.50-25 µg/L with a linearity coefficient of 0.9965 and 0.9987 were also obtained for trifluralin and chlorpyrifos, respectively. The method was applied successfully to analyze some real samples of cucumber, carrot, grape, and agriculture wastewater, and the results showed a relative recovery in the range of 87% to 110%.

Ex-situ and in-situ rapid and quantitative determination of benzene derivatives in seawater using nanoconfined liquid phase nanoextraction

Benzene derivatives (BDs) constitute a class of environmental pollutants whose exposure poses a grave risk to human health. These compounds rapidly diffuse from the atmosphere to the marine ecosystem: for this reason, their monitoring in seawater is every day more compelling. In this work, nanoconfined liquid phase nanoextraction (NLPNE), a versatile extraction technique recently described, has been for the first time applied to the gas chromatographic mass spectrometry (GC/MS) analysis of BDs in seawater. Ex-situ and in-situ NLPNE procedures have been developed and optimized in terms of extraction capabilities, analysis time, precision, and accuracy. Compared to the traditional extraction procedures, based on solid-phase microextraction (SPME) and liquid-liquid extraction (LLE), the proposed NLPNE methods allowed a rapid on-site analysis of benzene compounds with low solvent consumption, higher enrichment factors, and improved automation grade. Determination coefficients ranging from 0.9929 to 0.9997 were obtained for all BDs in the range 0.10-500 ng mL^-1 and 5.00-500 ng mL^-1, for ex-situ and in-situ NLPNE, respectively. Ex-situ and in-situ limits of detection ranged from 0.2 to 7.6 ng mL^-1 and 0.04-1.00 ng mL^-1. Our results suggest that NLPNE coupled to GC-MS can be considered a powerful technique for high-throughput analyses of trace compounds in environmental, food and biological samples.

Fluorescent noble metal nanoclusters for contaminants analysis in food matrix

Recently, food safety issues caused by contaminants have aroused great public concern. The development of innovative and efficient sensing techniques for contaminants detection in food matrix is in urgent demand. As fluorescent nanomaterials, noble metal nanoclusters have attracted much attention because of their ease of synthesis, enhanced catalytic activity and biocompatibility, and most importantly, excellent photoluminescence property that provides promising analytical applications. This review comprehensively introduced the synthesis method of noble metal nanoclusters, and summarized the application of metal nanoclusters as fluorescent sensing materials in the detection of pollutants, including pesticides, heavy metal, mycotoxin, food additives, and other contaminants in food. The detection mechanism of pesticide residues mostly relies on the inhibition of natural enzymes. For heavy metals, the detection mechanism is mainly related to the interaction between metal ions and nanoclusters or ligands. It is evidenced that metal nanoclusters have great potential application in the field of food safety monitoring. Moreover, challenges and future trends of nanoclusters were discussed. We hope that this review can provide insights and directions for the application of nanoclusters in contaminants detection.

A fluorinated chitosan-based QuEChERS method for simultaneous determination of 20 organophosphorus pesticide residues in ginseng using GC-MS/MS

In this study, a new fluorinated methacrylamide (MACF) was synthesized and evaluated as an adsorbent in the dispersive solid-phase extraction for the effective determination and extraction of 20 organophosphorus pesticides (OPPs) from ginseng samples using the QuEChERS (quick, easy, cheap, effective, rugged, safe) method coupled with GC-MS/MS. The properties of MACF were characterized using Fourier-transform infrared spectroscopy, elemental analysis, and high-resolution ¹⁹ F NMR. MACF, chitosan, primary and secondary amine, octadecylsilane, graphitized carbon black, Z-Sep, Z-Sep⁺ , and EMR-Lipid were compared in terms of extraction efficiency. The best results were obtained when MACF was used. Matrix-matched calibration was employed for quantification. All the OPPs exhibited good linearity (r²  > 0.9969) with the concentration at their respective concentration ranges. The limits of detection were 1.5-3.0 μg/kg, and the limits of quantification were 5.0-10.0 μg/kg. The trueness of the 20 pesticides at four spiked levels ranged from 86.1 to 111.1%, and the relative standard deviation was less than 11.3%. The modified QuEChERS method using MACF as the adsorbent was sensitive, reliable, and cost-effective and could be used for the determination of 20 OPP residues in ginseng.

Application of liquid-phase microextraction to the analysis of plant and herbal samples

INTRODUCTION

The analysis of plant and herbal samples is a challenging task for analytical chemists due to the complexity of the matrix combined with the low concentration of analytes. In recent years different liquid-phase microextraction (LPME) techniques coupled with a variety of analytical equipment have been developed for the determination of both organic and inorganic analytes.

OBJECTIVE

Over the past few years, the number of research papers in this field has shown a markedly growing tendency. Therefore, the purpose of this review paper is to summarise and critically evaluate research articles focused on the application of LPME techniques for the analysis of plant and herbal samples.

RESULTS

Due to the complex nature of the samples, the direct application of LPME techniques to the analysis of plants has not often been done. LPME techniques as well as their modalities have been commonly applied in combination with other pretreatment techniques, including a solid-liquid extraction technique supported by mechanical agitation or auxiliary energies for plant analysis. Applications and the most important parameters are summarised in the tables.

CONCLUSION

This review summarises the application of the LPME procedure and shows the major benefits of LPME, such as the low volume of solvents used, high enrichment factor, simplicity of operation and wide selection of applicable detection techniques. We can expect further development of microextraction analytical methods that focus on direct sample analysis with the application of green extraction solvents while fully automating procedures for the analysis of plant materials.

Supercritical Fluid Extraction of Pesticides and Insecticides from Food Samples and Plant Materials

The principal intention of this study is presenting the attempts carried out for extracting, separating, and determining of the pesticide and insecticide residues existing in food and plant samples. In this regard, a set of content, including the explanations about the supercritical fluid extraction (SFE), supercritical fluid chromatography, and various types of pesticides are indicated. Besides, the parameters affecting the pesticides extraction composed of temperature, pressure, modifier, drying agent, and so on are discussed. Also, examples of insecticides extraction by SFE technique as an important subset of pesticides are indicated. Along with these items, some interesting works, concerning the innovations implemented in the field of SFE of pesticide and insecticide residues from foodstuff and plants are depicted.

Determination of pyrethroid residues in herbal tea using temperature-controlled ionic liquid dispersive liquid-liquid microextraction by high performance liquid chromatography

A simple and effective method for determining five pyrethroid residues in herbal tea by ultrasound-enhanced temperature-controlled (UETC) ionic liquid dispersive liquid-liquid microextraction (IL-DLLME) coupled with high performance liquid chromatography-diode array detection (HPLC-DAD) was developed. The use of ultrasonication and heating improved the ability of the ionic liquid to extract the analytes. Various parameters that affect the extraction efficiency were investigated and optimized using single factor experiments and response surface design. The optimum conditions of the experiment were 121 µL of [HMIM][PF6] (extraction solvent), 794 µL of acetonitrile (dispersive solvent), a heating temperature of 40°C, a sonication time of 3.6 min and a pH of 2.9. Under optimized conditions, the linearity was in the range of 0.05–5 mg L⁻¹ with correlation coefficients above 0.9993. The limits of detection and quantification were 1.25–1.35 µg L⁻¹ and 5 µg L⁻¹, respectively. The mean recoveries of the five pyrethroids ranged from 74.02% to 109.01%, with RSDs below 9.04%. The proposed method was reliable for the analysis of pyrethroids in Chinese herbal tea.

Nanozyme-assisted technique for dual mode detection of organophosphorus pesticide

A novel dual-mode analytical method by employing nanozyme was developed for the detection of organophosphorus pesticides (OPP) for the first time. The detection principle is that the pesticide could be hydrolyzed to para-nitrophenol (p-NP) in the presence of nanoceria as nanozyme. p-NP exhibits the bright yellow color, and its color intensity has a positive correlation with the pesticide concentration. Meanwhile, the characteristic absorption peak at 400 nm of p-NP increases gradually with the raised concentration of pesticide. Therefore, a dual-mode method including smartphone-based colorimetric and spectroscopic strategies was rationally developed. Herein, methyl-paraoxon was selected as the representative compound. Under the optimum conditions, the detection limits of both two strategies were calculated to be 0.42 μmol L^-1. Finally, the present method was successfully applied in three edible medicinal plants (Semen nelumbinis, Semen Armeniacae Amarum, Rhizoma Dioscoreae). The present work offers a reliable and convenient approach for routine detection of pesticide based on two different detection mechanisms.

A Vortex-Assisted Dispersive Liquid-Liquid Microextraction Followed by UPLC-MS/MS for Simultaneous Determination of Pesticides and Aflatoxins in Herbal Tea

A method for detecting the organophosphorus pesticides residue and aflatoxins in China herbal tea has been developed by UPLC-MS/MS coupled with vortex-assisted dispersive liquid-liquid microextraction (DLLME). The extraction conditions for vortex-assisted DLLME extraction were optimized using single-factor experiments and response surface design. The optimum conditions for the experiment were the pH 5.1, 347 µL of chloroform (extraction solvent) and 1614 µL of acetonitrile (dispersive solvent). Under the optimum conditions, the targets were good linearity in the range of 0.1 µg/L⁻25 µg/L and the correlation coefficient above 0.9998. The mean recoveries of all analytes were in the ranged from 70.06%⁻115.65% with RSDs below 8.54%. The detection limits were in the range of 0.001 µg/L⁻0.01µg/L. The proposed method is a fast and effective sample preparation with good enrichment and extraction efficiency, which can simultaneously detect pesticides and aflatoxins in China herbal tea.

The in-capillary- 2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)-sweeping micellar electrokinetic chromatography - Diode array detector method for screening and quantifying trace natural antioxidants from Schisandra chinensis

An in-capillary 2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)-sweeping micellar electrokinetic chromatography-diode array detector (ABTS⁺-sweeping MEKC-DAD) method was developed and successfully applied to screening and quantifying antioxidative ingredients from natural products. The parameters affecting sweeping and separation were optimized including components of background electrolyte and sample matrix. Comparing with previously reported MEKC, the sensitivity enhancement factors of trace natural antioxidants obtained by this proposed method were from 17 to 167. The limit of detection was as low as 6 ng·mL^-1. The results of other validation parameters including linearity, reproducibility, accuracy and recovery were satisfactory. Seven compounds including schizandrin, schisandrol B, schisantherin B, schisantherin A, schisanhenol, deoxyschizandrin, schisandrin B were identified as the main antioxidants in Schisandra chinensis. It was demonstrated that this developed in-capillary ABTS⁺-sweeping MEKC-DAD is simple, sensitive, reliable and rapid method for screening and quantifying trace antioxidants from natural products.

Fluorometric determination of pesticides and organophosphates using nanoceria as a phosphatase mimic and an inner filter effect on carbon nanodots

Nanoceria with a remarkable phosphatase mimicking activity was synthesized and used to catalyze the hydrolysis of phosphate esters in pH 10 solution. The catalytic effect of nanoceria was firstly investigated by selecting p-nitrophenyl phosphate as a model substrate. The pH value, incubation temperature, reaction time, and concentration of nanoceria were optimized. The catalytic effect was then confirmed by using methyl-paraoxon as a substrate. The p-nitrophenol anion released by the enzyme mimic is yellow and exerts an inner filter effect on the fluorescence of the carbon dots (with excitation/emission maxima at 400/520 nm). Response to methyl-paraoxon is linear in the 1.125-26.25 μmol L^-1 concentration range. The method was applied to the determination of pesticides in spiked Panax quinquefolius and water samples. Recoveries ranged from 85 to 103% (n = 3). The technique is rapid, reliable, and can be used for on-site detection of pesticides and organophosphates. Graphical abstract Schematic presentation of a fluorometric technique for the detection of organophosphate compound and pesticide using nanoceria as a phosphatase mimic and an inner filter effect on the blue fluorescence of carbon dots (with excitation/emission maxima at 400/520 nm).

Ultrasound-assisted dispersive liquid-liquid microextraction followed by ion mobility spectrometry for the simultaneous determination of bendiocarb and azinphos-ethyl in water, soil, food and beverage samples

A sensitive and fast ultrasound-assisted dispersive liquid-liquid microextraction procedure combined with ion mobility spectrometry has been developed for the simultaneous extraction and determination of bendiocarb and azinphos-ethyl. Experimental parameters affecting the analytical performance of the method were optimized: type and volume of extraction solvent (chloroform, 150 µL), pH (9.0), type and volume of buffer (ammonium buffer pH = 9.0, 4.5 mL) and extraction time (3.0 min). Under optimum conditions, the linearity was found to be in the range of 2-40 and 6-100 ng/mL and the limits of detection (LOD) were 1.04 and 1.31 ng/mL for bendiocarb and azinphos-ethyl, respectively. The method was successfully validated for the analysis of bendiocarb and azinphos-ethyl in different samples such as waters, soil, food and beverage samples.

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2016-2018)

One of the most cited limitations of capillary and microchip electrophoresis is the poor sensitivity. This review continues to update this series of biannual reviews, first published in Electrophoresis in 2007, on developments in the field of online/in-line concentration methods in capillaries and microchips, covering the period July 2016-June 2018. It includes developments in the field of stacking, covering all methods from field-amplified sample stacking and large-volume sample stacking, through to isotachophoresis, dynamic pH junction, and sweeping. Attention is also given to online or in-line extraction methods that have been used for electrophoresis.

Trace determination of carbamate pesticides in medicinal plants by a fluorescent technique

The safety issue of using carbamate pesticides in medicinal plants (MPs) has been a global concern and hence attracted attention of many researchers to develop analytical tools for trace pesticides detection. Derived from the fluorescence-based techniques, a rapid, convenient and efficient method for the detection of three carbamate pesticides, including carbofuran, aldicarb and methomyl has been developed by using core-shell QDs. By optimizing experimental parameters, the system demonstrated high detection sensitivities for the investigated carbamates, with the lowest detectable concentrations less than 0.05 μM. The molecular docking study indicated that the selected carbamate pesticides bound to the catalytic active site of acetylcholinesterase via π-π or H-π interactions, which also revealed the potential mechanism of the differences in inhibition strength among the three pesticides on AChE. Moreover, in order to investigate the applicability and reliability of the proposed method for the pesticide analysis in real sample with complex matrix, the matrix effects of eight common MPs have been systematically explored. These findings suggested that this technique was a simple, sensitive and reliable method for rapid determination of carbamate pesticides in real samples, especially those with complex matrices like MPs, vegetables, fruits, and other agricultural crops.

Sensitive and Selective Detection of Oxo-Form Organophosphorus Pesticides Based on CdSe/ZnS Quantum Dots

A rapid, sensitive and enzyme-based optical biosensor was applied for the determination of seven organophosphorus pesticides (OPPs), including the oxo forms (malaoxon, paraoxon, dibrom, and dichlorvos), the thio forms (malathion and parathion) and the mixed form (demeton) in Panax ginseng. The principal of the proposed method is that the fluorescence quenching effect of quantum dots (QDs) can be observed by enzyme-generated H₂O₂. The active centers of acetylcholinesterase (AChE) could be inhibited in the presence of pesticides, which caused decrease of the generated H₂O₂. Then, the inhibition efficiency of pesticide to AChE activity could be evaluated by measuring the fluorescence changes. Different from biosensors based on immobilized enzyme or self-assembling technique, the proposed biosensor demonstrated a good selectivity for the detection of oxo forms of OPPs. In the present study, the important experimental conditions of the proposed biosensor were investigated. Under the optimized conditions (incubation temperature, 35 °C; incubation time, 20 min; pH value, 8.0; detection time, 30 min; AChE concentration, 40.9 U/L; and choline oxidase (ChOx) concentration, 637.5 U/L), the limit of detection for the investigated oxo-form OPPs was no more than 0.05 μM, which suggested that the proposed method could be used for sensitive and selective determination of trace amounts of OPPs residues in real samples with complex matrices.

Recent progress of sample stacking in capillary electrophoresis (2014-2016)

The term "sample stacking" comprises a relatively broad spectrum of techniques that already form an almost inherent part of the methodology of CZE. Their principles are different but the effect is the same: concentration of a diluted analyte into a narrow zone and considerable increase of the method sensitivity. This review brings a survey of papers on electrophoretic sample stacking published approximately since the second quarter of 2014 till the first quarter of 2016. It is organized according to the principles of the stacking methods and includes chapters aimed at the concentration adjustment principle (Kohlrausch stacking), techniques based on pH changes, micellar methods, and other stacking techniques. Not reviewed are papers on transient ITP that are covered by another review in this issue.