Optimisation of a solid-phase microextraction/HPLC/Diode Array method for multiple pesticide screening in lettuce

Imidazolium-decorated Bis-cyanostilbene Macrocycle: An Effect Fluorescence Sensor for Pesticide Starane

Fluorescence sensors for complicated molecules such as pesticides were paid much attention lately due to the merits of simple operation, high sensitivity and selectivity, and in-situ detection. In this work, a novel fluorescent sensor for pesticide starane was prepared based on imidazolium-decorated bis-cyanostilbene macrocycle (IBM). IBM exhibited the obvious "turn-on" fluorescence change from dark blue-green to bright blue after sensing starane with the high sensing selectivity among 28 kinds of guests. The detecting limitation was as low as 0.011 μM, which was the lowest one in literatures. The sensing mechanism was confirmed as that starane was located in cavity of IBM based on the molecular interaction of multiple hydrogen bonds, π-π stacking and hydrophobic interaction. The application experiments suggested that starane was examined well on test paper with good selectivity and was quantitatively detected in water samples, implying the good real-time and in-situ application potential for IBM on sensing starane in real environment and daily life.

A review of aptamer-conjugated nanomaterials for analytical sample preparation: Classification according to the utilized nanomaterials

BACKGROUND

Sample extraction before detection is a critical step in analysis. Since targets of interest are often found in complex matrices, the sample can not be directly introduced to the analytical instrument. Nanomaterials with unique physical-chemical properties are excellent supports for use in sorbent-based extraction. However, they lack selectivity and thus need to be functionalized with target-capturing molecules. Antibodies and molecularly imprinted polymers (MIPs) can be used for this purpose, but they have some problems that limit their practical applications. Hence, functionalization of nanomaterials for selectivity remains a problem.

RESULTS

Nucleic acid aptamers are affinity reagents that can provide superiority to antibodies since they can be selected in vitro and at a lower cost. Moreover, aptamers can be chemically synthesized and easily modified with different functional groups. Hence, aptamers are good candidates to impart selectivity to the nanomaterials. Recent studies focus on the integration of aptamers with magnetic nanoparticles, carbon-based nanomaterials, metal-organic frameworks, gold nanoparticles, gold nanorods, silica nanomaterials, and nanofibers. The unique properties of nanomaterials and aptamers make the aptamer-conjugated nanomaterials attractive for use in sample preparation. Aptamer-functionalized nanomaterials have been successfully used for selective extraction of proteins, small molecules, and cells from different types of complex samples such as serum, urine, and milk. In particular, magnetic nanoparticles have a wider use due to the rapid extraction of the sample under magnetic field.

SIGNIFICANCE

In this review, we aim to emphasize how beneficial features of nanomaterials and aptamers could be combined for extraction or enrichment of the analytes from complex samples. We aim to highlight that the benefits are twofold in terms of selectivity and efficiency when employing nanomaterials and aptamers together as a single platform.

Solid-Phase Microextraction Techniques and Application in Food and Horticultural Crops

Solid-phase microextraction (SPME) is a sample preparation technique which utilizes small amounts of an extraction phase for the extraction of target analytes from investigated sample matrices. Its simplicity of use, relatively short sample processing time, and fiber reusability have made SPME an attractive choice for many analytical applications. SPME has been widely applied to the sampling and analysis of environmental, food, aromatic, metallic, forensic, and pharmaceutical samples. Solid phase microextraction is used in horticultural crops, for example, to determine water and soil contaminants (pesticides, alcohols, phenols, amines, herbicides, etc.). SPME is also used in the food industry to separate biologically active substances in food products for various purposes, for example, disease prevention, determining the smell of food products, and analyzing tastes. SPME has been applied to forensic analysis to determine the alcohol concentration in blood and that of sugar in urine. This method has also been widely used in pharmaceutical analysis. It is a solvent-free sample preparation technique that integrates sampling, isolation, and concentration. This review focuses on recent work on the use of SPME techniques in the analysis of food and horticultural crops.

Improved procedure for square-wave voltammetric sensing of fenhexamid residues on blueberries peel surface at the anodically pretreated boron-doped diamond electrode

BACKGROUND

Fungicide fenhexamid (FH) has a high residual concentration on fruits and vegetables, thus, it is of high importance to monitor the level of FH residues on foodstuff samples. So far, the assay of FH residues in selected foodstuff samples has been conducted by electroanalytical methods on sp² carbon-based electrodes that are well-known to be susceptible to severe fouling of the electrodes surfaces during electrochemical measurements. As an alternative, sp³ carbon-based electrode such as boron-doped diamond (BDD) can be used in the analysis of FH residues retained on the peel surface of foodstuff (blueberries) sample.

RESULTS

In situ anodic pretreatment of the BDDE surface was found to be the most successful strategy to remediate the passivated BDDE surface by FH oxidation (by)products, and the best validation parameters, i.e., the widest linear range (3.0-100.0 μmol L^-1), the highest sensitivity (0.0265 μA L μmol^-1) and the lowest limit of detection (0.821 μmol L^-1), were achieved on the anodically pretreated BDDE (APT-BDDE) in a Britton-Robinson buffer, pH 2.0, using square-wave voltammetry (SWV). The assay of FH residues retained on blueberries peel surface was performed on the APT-BDDE using SWV, and the obtained concentration of FH residues of 6.152 μmol L^-1 (1.859 mg kg^-1) was found to be below the maximum residue value fixed for blueberries by the European Union regulations (20 mg kg^-1).

SIGNIFICANCE AND NOVELTY

In this work, a protocol based on a very easy and fast foodstuff sample preparation procedure combined with the straightforward pretreatment approach of the BDDE surface was elaborated for the first time for the monitoring of the level of FH residues retained on the peel surface of blueberries samples. The presented reliable, cost-effective, and easy-to-use protocol could find its application as a rapid screening method for the control of food safety.

Review: Microextraction Technique Based New Trends in Food Analysis

Food chemistry is the study and classification of the quality and origin of foods. The identification of definite biomarkers and the determination of residue contaminants such as toxins, pesticides, metals, human and veterinary drugs, which are a very common source of food-borne diseases. The food analysis is continuously demanding the improvement of more robust, sensitive, highly efficient, and economically beneficial analytical approaches to promise the traceability, safety, and quality of foods in the acquiescence with the consumers and legislation demands. The traditional methods have been used at the starting of the 20th century based on wet chemical methods. Now it existing the powerful analytical techniques used in food analysis and safety. This development has led to substantial enhancements in the analytical accuracy, precision, sensitivity, selectivity, thereby mounting the applied range of food applications. In the present decade, microextraction (micro-scale extraction) pays more attention due to its futures such as low consumption of solvent and sample, throughput analysis easy to operate, greener, robotics, and miniaturization, different adsorbents have been used in the microextraction process with unique nature recognized with wide range applications.

Dissipation Profiles of Tristyrylphenol Ethoxylate Homologs in Lettuce under Greenhouse and Field Conditions

Tristyrylphenol ethoxylates (TSPEOs) have been increasingly used in pesticide formulations as inert ingredients in China, but little information exists on the dissipation behavior of TSPEOs in foodstuffs. In this work, a rapid method for measuring TSPEO homologs in lettuce using QuEChERS and HPLC-MS/MS was established. This method was used to study the dissipation and distribution profiles of TSPEOs in lettuce. TSPEO homologs degraded rapidly under greenhouse and field conditions, with half-lives of 2.18-5.39 and 1.82-5.52 days, respectively. TSPEOn (n = 6-9) were relatively persistent in the field. The distribution profiles showed an obvious difference between the two conditions. TSPEOn (n = 14-18) degraded to shorter-chain TSPEOs with time, and a two-peak (TSP16EO and TSP10EO) homolog distribution profile occurred between 7 and 14 days of treatment under greenhouse conditions. This work improves the understanding of the dissipation behavior of TSPEO homologs in lettuce.

Assessment of strobilurin fungicides' content in soya-based drinks by liquid micro-extraction and liquid chromatography with tandem mass spectrometry

Seven strobilurin fungicides were pre-concentrated from soya-based drinks using dispersive liquid-liquid micro-extraction (DLLME) with a prior protein precipitation step in acid medium. The enriched phase was analysed by liquid chromatography (LC) with dual detection, using diode array detection (DAD) and electrospray-ion trap tandem mass spectrometry (ESI-IT-MS/MS). After selecting 1-undecanol and methanol as the extractant and disperser solvents, respectively, for DLLME, the Taguchi experimental method, an orthogonal array design, was applied to select the optimal solvent volumes and salt concentration in the aqueous phase. The matrix effect was evaluated and quantification was carried out using external aqueous calibration for DAD and matrix-matched calibration method for MS/MS. Detection limits in the 4-130 and 0.8-4.5 ng g(-1) ranges were obtained for DAD and MS/MS, respectively. The DLLME-LC-DAD-MS method was applied to the analysis of 10 different samples, none of which was found to contain residues of the studied fungicides.

Determination and analysis of the dissipation and residue of cyprodinil and fludioxonil in grape and soil using a modified QuEChERS method

A simple and accurate method coupled with a gas chromatography-nitrogen phosphorus detector was developed to detect cyprodinil and fludioxonil in grape and soil. The accuracy and precision of the method in detecting the two fungicides were evaluated by conducting intra- and inter-day recovery experiments. The limits of detection were 0.017 mg/kg for cyprodinil and 0.030 mg/kg for fludioxonil. The limits of quantitation were 0.05 mg/kg for cyprodinil and 0.10 mg/kg for fludioxonil in grape and soil. The recoveries of the fungicides in grape and soil were investigated at three spiked levels and were found to range from 85.81 to 102.94% for cyprodinil and from 92.00 to 106.86% for fludioxonil, with relative standard deviations below 7%. Field experiments were conducted in two experimental locations in China. The half-lives of cyprodinil were 9.6-20.8 days in grape and 5.8-15.6 day in soil, and the half-lives of fludioxonil were 6.2-7.2 days in grape and 6.0-12.1 days in soil. When the cyprodinil and fludioxonil 62% water-dispersible granule formulation was sprayed at a low dosage three times, terminal residues of cyprodinil and fludioxonil were below 1.0 mg/kg in grape 14 days after harvest. This work may serve as a reference to establish the maximum residue limits for cyprodinil and fludioxonil in grape and promote the proper and safe use of these two fungicides.

Optimization of derivatization procedure and gas chromatography-mass spectrometry method for determination of bensulfuron-methyl herbicide residues in water

A simple and efficient technique based on liquid phase extraction with CH2Cl2 solvent followed by derivatization with (C2H5)2O·BF3 solution and confirmation analysis with GC-MS analytical method was developed for detecting the bensulfuron-methyl (BSM) residues in water. Box-Behnken response surface methodology was employed for optimization of the derivatization efficiency. According to the optimization model, the derivatization time of 45min, derivatization temperature at 55°C and 0.2mL (C2H5)2O·BF3 solvent were selected as the optimal derivatization condition for obtaining the maximum desirability of response. Method validation was performed at 6 working standard levels (0.05, 0.1, 0.2, 0.5, 1.0, 5.0μg/mL) and the linearity of the calibration curve was linear well over the 6 fortification levels with the squared correlation coefficient of determination r(2)=0.998 and the LOD was found to be 0.1μg/L for BSM herbicide. The mean value of BSM was detected from 0.0414 to 4.7542μg/mL at levels from 0.05 to 5μg/mL with the recoveries remained at the acceptable level (42.8-95.0%) with the RSD values from 3.5% to 6.2%, which is more accptable and desirable than the results obtained by LC methods. Moreover, the method allowed the determination of BSM residue in real paddy field water samples at concentrations between 0.0902 and 3.4605μg/L. Average recovery rates of the BSM spiked at levels 0.1, 0.2, 0.5, 1.0μg/mL into thirty water samples ranged from 74.1% and 94.1% with the relative standard derivation (RSD) values from 1.9% to 6.7%.

Sensitive quantitation of polyamines in plant foods by ultrasound-assisted benzoylation and dispersive liquid-liquid microextraction with the aid of experimental designs

A new method involving ultrasound-assisted benzoylation and dispersive liquid-liquid microextraction was optimized with the aid of chemometrics for the extraction, cleanup, and determination of polyamines in plant foods. Putrescine, cadaverine, spermidine, and spermine were derivatized with 3,5-dinitrobenzoyl chloride and extracted by dispersive liquid-liquid microextraction using acetonitrile and carbon tetrachloride as dispersive and extraction solvents, respectively. Two-level full factorial design and central composite design were applied to select the most appropriate derivatization and extraction conditions. The developed method was linear in the 0.5-10.0 mg/L range, with a R(2) ≥ 0.9989. Intra- and interday precisions ranged from 0.8 to 6.9% and from 3.0 to 10.3%, respectively, and the limit of detection ranged between 0.018 and 0.042 μg/g of fresh weight. This method was applied to the analyses of six different types of plant foods, presenting recoveries between 81.7 and 114.2%. The method is inexpensive, versatile, simple, and sensitive.

Microextraction techniques for the determination of volatile and semivolatile organic compounds from plants: a review

Vegetables and fruits are necessary for human health, and traditional Chinese medicine that uses plant materials can cure diseases. Thus, understanding the composition of plant matrix has gained increased attention in recent years. Since plant matrix is very complex, the extraction, separation and quantitation of these chemicals are challenging. In this review we focus on the microextraction techniques used in the determination of volatile and semivolatile organic compounds (such as esters, alcohols, aldehydes, hydrocarbons, ketones, terpenes, sesquiterpene, phenols, acids, plant secondary metabolites and pesticides) from plants (e.g., fruits, vegetables, medicinal plants, tree leaves, etc.). These microextraction techniques include: solid phase microextraction (SPME), stir-bar sorptive extraction (SBSE), single drop microextraction (SDME), hollow fiber liquid phase microextraction (HF-LPME), dispersive liquid liquid microextraction (DLLME), and gas purge microsyringe extraction (GP-MSE). We have taken into consideration papers published from 2008 to the end of January 2013, and provided critical and interpretative review on these techniques, and formulated future trends in microextraction for the determination of volatile and semivolatile compounds from plants.

Determination of polycyclic aromatic hydrocarbons in smoked fish samples by a new microextraction technique and method optimisation using response surface methodology

Microwave-assisted extraction coupled with dispersive liquid-liquid microextraction as a recently introduced method was applied to determine polycyclic aromatic hydrocarbons in Iranian smoked fish. The results showed that the interaction of hydrolysing solution volume with ethanol ratio, volumes of extracting and disperser solvent is significant in the obtained model. Optimized conditions were: a hydrolysing solution volume 10 ml with 50% ethanol, a pH of 5, and extracting and disperser solvent volumes of 150 and 500 μl respectively. The level of 16 polycyclic aromatic hydrocarbons (PAHs) was determined in 80 smoked fish consisting of four species. The contamination of benzo[a]pyrene in all samples except three was below the European Commission's maximum level of 2 μg kg(-1) for smoked fish, while the ∑4 PAHs (benzo[a]pyrene, chrysene, benzo[a]anthracene and benzo[b]fluoranthene) were between 3 and 12 μg kg(-1) wet weight in all samples. Of the species examined, Hypophthalmichthys molitrix had the highest PAHs (∑16).

Immunoreagent generation and competitive assay development for cyprodinil analysis

Cyprodinil is an anilinopyrimidine fungicide applied worldwide for the prevention and treatment of highly destructive plant diseases in a large variety of crops, including cereals, fruits, and vegetables. This paper describes the development of the first reported immunoassays for cyprodinil. Two original haptens have been synthesized and conjugated to different carrier proteins, and polyclonal antibodies have been produced. Moreover, competitive enzyme-linked immunosorbent assays have been developed and characterized for the analysis of this widely used pesticide. The influence of organic solvents and buffer conditions over the assay analytical parameters was studied. The IC(50) values of the optimized immunoassays were 1.6 and 2.8 ng/mL for the direct and indirect formats, respectively. Quantitative recoveries were found using spiked apple and grape juice samples after a simple direct dilution, and a limit of quantification of 20 ng/mL for both fruit matrices was achieved. These immunoreagents could be very valuable for the sensitive, straightforward, and rapid monitoring of cyprodinil residues in foodstuffs.