Determination of multi-pesticide residues in green tea with a modified QuEChERS protocol coupled to HPLC-MS/MS

Nanoparticles Based Extraction Strategies for Accurate and Sensitive Determination of Different Pesticides

Sample preparation methods have become indispensable steps in analytical measurements not only to lower the detection limit but also to eliminate the matrix effect although more sophisticated instruments are being commonly used in routine analyses. Solid phase extraction (SPE) is one of the main extraction/preconcentration methods used to extract and purify target analytes along with simple and rapid procedures but some limitations have led to seek for an easy, sensitive and fast extraction methods with analyte-selective sorbents. Nanoparticles with different modifications have been used as spotlight to enhance extraction efficiency of target pesticides from complicated matrices. Carbon-based, metal and metal oxides, silica and polymer-based nanoparticles have been explored as promising sorbents for pesticide extraction. In this review, different types of nanoparticles used in the preconcentration of pesticides in various samples are outlined and examined. Latest studies in the literature are discussed in terms of their instrumental detection, sample matrix and limit of detection values. Novel strategies and future directions of nanoparticles used in the extraction and preconcentration of pesticides are also discussed.

Simultaneous determination of spirodiclofen, spiromesifen, and spirotetramat and their relevant metabolites in edible fungi using ultra-performance liquid chromatography/tandem mass spectrometry

A fast, sensitive, and reliable analytical method was developed and validated for simultaneous identification and quantification of spirodiclofen, spiromesifen, and spirotetramat and their relevant metabolites in edible fungi by ultra-performance liquid chromatography/tandem mass spectrometry (UHPLC–MS/MS). First, sample extraction was done with acetonitrile containing 1% formic acid followed by phase separation with the addition of MgSO₄:NaOAc. Then, the supernatant was purified by primary secondary amine (PSA), octadecylsilane (C18), and graphitized carbon black (GCB). The linearities of the calibrations for all analytes were excellent (R² ≥ 0.9953). Acceptable recoveries (74.5–106.4%) for all analytes were obtained with good intra- and inter- relative standard deviations of less than 14.5%. The limit of quantification (LOQs) for all analytes was 10 μg kg⁻¹. For accurate quantification, matrix-matched calibration curve was applied to normalize the matrix effect. The results indicated that the method was suitable for detecting the three acaricides and their relevant metabolites in edible fungi.

A QuEChERS-HPLC-MS/MS Method with Matrix Matching Calibration Strategy for Determination of Imidacloprid and Its Metabolites in Procambarus clarkii (Crayfish) Tissues

We developed a method for determination of imidacloprid and its metabolites 5-hydroxy imidacloprid, olefin imidacloprid, imidacloprid urea and 6-chloronicotinic acid in Procambarus clarkii (crayfish) tissues using quick, easy, cheap, effective, rugged, and safe (QuEChERS) and high-performance liquid chromatography-triple quadrupole mass spectrometry. Samples (plasma, cephalothorax, hepatopancrea, gill, intestine, and muscle) were extracted with acetonitrile containing 0.1% acetic acid and cleaned up using a neutral alumina column containing a primary secondary amine. The prepared samples were separated using reverse phase chromatography and scanned in the positive and negative ion multiple reaction-monitoring modes. Under the optimum experimental conditions, spiked recoveries for these compounds in P. clarkii samples ranged from 80.6 to 112.7% with relative standard deviations of 4.2 to 12.6%. The limits of detection were 0.02-0.5 μg·L^-1, the limits of quantification were 0.05-2.0 μg·L^-1 and the method of quantification was 0.05-2.0 μg·kg^-1. The method is rapid, simple, sensitive and suitable for rapid determination and analysis of imidacloprid and its metabolites in P. clarkii tissues.

A novel sample-preparation method for the generic and rapid determination of pesticides and mycotoxins in tea by ultra-performance liquid chromatography-tandem mass spectrometry

A rapid, simple, and generic analytical method for the simultaneous determination of 140 undesirable low-weight pesticides and mycotoxins from different chemical classes in black tea was developed. The method involved swelling the sample in ammonium acetate buffer, extraction with acetonitrile-dimethyl sulfoxide, cleanup by dual dispersive solid-phase extraction (D-SPE) with the assistance of low-temperature centrifugation, and analysis by ultraperformance liquid chromatography coupled with electrospray ionization tandem mass spectrometry using multiple reaction monitoring mode. The interferences in the extract were eliminated by the combination of dual d-SPE using only C₁₈ sorbent and anhydrous magnesium sulfate, which maintained the chromatographic column under the ideal condition for a long time and enabled satisfactory recoveries of hydrophobic and hydrophilic analytes simultaneously. Matrix-matched calibration curves were obtained for most target compounds with linear regression coefficients above 0.9900. The limits of quantification (LOQs) ranged within 0.5-10.0 μg/kg, which were usually sufficient to verify the compliance of products with legal tolerances. Satisfactory recoveries of 64.5%-138.1% were obtained in black ta samples with the relative standard deviation (RSD) values between 1.8 and 25.9%. The inter-day precision ranged within 2.2%-24.9%. For over 90% of the analytes, the recoveries were between 70% and 120%, with RSD values below 15.0%. The application of this method in routine monitoring programs can drastically reduce effort and time.

A syringe-aided apta-nanosensing method for colorimetric determination of acetamiprid

A syringe-aided apta-nanosensing method is reported for the colorimetric determination of acetamiprid. The method employs double-stranded (ds) DNA-conjugated gold nanoparticle@magnetic agarose beads, i.e., dsDNA-AuNP@MABs as peroxidase-mimicking composite probes, in which the aptamer is indirectly attached to the AuNP surface through its hybridization with complementary DNA (cDNA). Upon contact with the acetamiprid target, the probes can give perceptible color change due to the possible conformation switch from dsDNA's brush-like to cDNA's 'pancake' regime. An "air-spaced pumping" procedure using a syringe equipped with ring magnets as the operation platform was proposed to facilitate the magnetic separation of the sensing probes. Therefore, the analytical steps can be easily accomplished in a syringe, including probe loading, acetamiprid capture and magnetic separation from crude samples, chromogenic reagent loading and colorimetric visualization. Acetamiprid concentration down to 3.3 ppb can be easily identified by the naked eye. The final solution also can be transferred for quantitative measurement. Under spectrometer, the ratio of the absorbance at 652 nm in the presence and absence of acetamiprid (A/A₀) is linearly related to the acetamiprid concentration in the 0.4-4.5 ppb range. The limit of detection is calculated to be 0.24 ppb. Moreover, satisfactory recoveries ranging from 90.90 to 91.82% with relative standard deviations of ≤2.96% were obtained in analyzing real spiked samples.

Chromatographic Methods for Detection and Quantification of Carbendazim in Food

Carbendazim (CBZ), which is a fungicide widely used for the management of plant diseases, has been detected in a number of food products. The negative effects of CBZ to human health have stimulated the reduction of the maximum residue limits (MRLs), and subsequently the development of reliable and sensitive detection methods. Here, we are reviewing for the first time all reported chromatographic methods for the detection and quantification of CBZ in food. Several techniques, including liquid chromatography (LC), thin layer chromatography (TLC), micellar electrokinetic chromatography (MEKC), and supercritical fluid chromatography (SFC), were used for the separation and detection of CBZ, showing diverse characteristics and sensitivity. Some methods allowed the specific determination of CBZ, whereas other methods were successfully applied for the simultaneous quantification of a huge number of pesticides. Most reported methods showed limits of detection (LOD) and quantification (LOQ) lower than the MRLs. Relevant efforts in the field have been directed toward the simplification and optimization of the extraction steps prior to the chromatographic separation to increase the recovery and reduce the matrix effects. In this Review, the matrices, extraction procedures, and separation and detection parameters are detailed and compared in order to provide new insights on the development of new reliable methods for the detection of CBZ in food.

Fast and Low-Cost Surface-Enhanced Raman Scattering (SERS) Method for On-Site Detection of Flumetsulam in Wheat

The pesticide residues in agri-foods are threatening people’s health. This study aims to establish a fast and low-cost surface-enhanced Raman scattering (SERS) method for the on-site detection of flumetsulam in wheat. The two-step modified concentrated gold nanoparticles (AuNPs) acted as the SERS substrate with the aid of NaCl and MgSO₄. NaCl is served as the activator to modify AuNPs, while MgSO₄ is served as the aggregating agent to form high-density hot spots. The activation and aggregation are two essential collaborative procedures to generate remarkable SERS enhancement and achieve the trace-level detection of flumetsulam. This method exhibits good enhancement effect with an enhancement factor of 10⁶ and wide linear range (5–1000 μg/L). With simple pretreatment, the flumetsulam residue in real wheat samples can be successfully detected with the limit of detection (LOD) down to 0.01 μg/g, which is below the maximum residue limit of flumetsulam in wheat (0.05 μg/g) set in China. The recovery of flumetsulam residue in wheat ranges from 88.3% to 95.6%. These results demonstrate that the proposed SERS method is a powerful technique for the detection of flumetsulam in wheat, which implies the great application potential in the rapid detection of other pesticide residues in various agri-foods.

Simultaneous determination of 11 antiseptic ingredients in surface water based on polypyrrole decorated magnetic nanoparticles

With the emergence and spread of coronavirus COVID-19, the use of personal cleansing, medical and household disinfectant products have increased significantly. In this work, a new magnetic solid-phase extraction (MSPE) method for the determination of 11 antiseptic ingredients in surface water by high performance liquid chromatography-mass spectrometry (HPLC-MS/MS) for 6 months based on Fe3O4@PPy magnetic nanoparticles (MNPs) was established. The MSPE method possessed the advantages of simple processing, little time consumption and less organic solvent consumption, and the MNPs could be reused several times. The analytical parameters influencing the extraction efficiency, such as sample pH, amount of MNPs and extraction time, were optimized in detail. It was indicated that the method had satisfactory linearities in the range of 0.50 to 1000.0 μg L-1 with the correlation coefficients (r) higher than 0.9996. Additionally, satisfactory spiked recoveries were achieved in the range of 80.21-107.33% with relative standard deviations (RSDs) from 1.98% to 8.05%. The limits of detection (LODs) and limits of quantitation (LOQs) were in the range of 0.20 to 2.0 μg L-1 and 0.50 to 5.0 μg L-1. Therefore, the developed MSPE-HPLC-MS/MS method has high selectivity and stability, and satisfactory quantitative capability for the antiseptic ingredients in surface water. Furthermore, this method can provide relevant technical support for the development of surface water standards.

Screening of multiclass pesticide residues in maca and Moringa oleifera by a modified QuEChERS sample preparation procedure and UPLC-ESI-MS/MS analysis

In the present study, a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method was proposed for the simultaneous analysis of 75 pesticides in maca and Moringa oleifera with ultra-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS). The developed method was validated in accordance with linearity, linear range, limit of detection, limit of quantification, accuracy, precision, and matrix effect. Each analyte had good linearity (R² > 0.99) in the corresponding concentration range. The method LOD and LOQ values of all the analytes ranged from 0.01 μg kg⁻¹ to 303.35 μg kg⁻¹ and 0.03 μg kg⁻¹ to 1011.15 μg kg⁻¹, respectively. The recoveries (n = 6) of the analyzed pesticides were in the range of 75.92–113.43%. The RSDs of precision were between 0.60% and 7.36%. All matrix effect values ranged from 81.79% to 118.71% and 80.36% to 119.64% in maca and Moringa oleifera, respectively. The analysis of 103 samples showed the presence of isofenphos-methyl in some of them. The method had a good application prospect and could be used as a general approach for the quantitative determination of pesticide residues in food.

In the present study, a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method was proposed for the simultaneous analysis of 75 pesticides in maca and Moringa oleifera with UPLC-ESI-MS/MS.

Silver microspheres aggregation-induced Raman enhanced scattering used for rapid detection of carbendazim in Chinese tea

Due to the excessive use of fungicides, pesticide residues have become a growing concern in recent years. Herein, we demonstrated an easy-prepared and low-cost surface enhanced Raman Scattering (SERS) chip composed of 3D silver microspheres (AgMSs) pattern for the quantitative testing of carbendazim in Chinese tea. Compared with the common monolayer SERS substrate, the 3D patterns formed by self-assembly AgMSs with fine nanostructure can offer much more aggregation-induced hotspots and generate strong 3D synergetic effects. Furthermore, when the thickness of the 3D pattern exceeded 6 μm, we replaced the conductive supporting coatings using the glass slides to reduce the cost without any impact on SERS properties. The prepared 3D chips achieved the determination of carbendazim within the linear range of 0.1-10 mg/L and the detection limit of 0.01 mg/L. It is simple and sensitive enough for the detection of most pesticide residues or other harmful organic molecules in our food or environment.

Rapid Quantitative Detection of Deltamethrin in Corydalis yanhusuo by SERS Coupled with Multi-Walled Carbon Nanotubes

With the increase in demand, artificially planting Chinese medicinal materials (CHMs) has also increased, and the ensuing pesticide residue problems have attracted more and more attention. An optimized quick, easy, cheap, effective, rugged and safe (QuEChERS) method with multi-walled carbon nanotubes as dispersive solid-phase extraction sorbents coupled with surface-enhanced Raman spectroscopy (SERS) was first proposed for the detection of deltamethrin in complex matrix Corydalis yanhusuo. Our results demonstrate that using the optimized QuEChERS method could effectively extract the analyte and reduce background interference from Corydalis. Facile synthesized gold nanoparticles with a large diameter of 75 nm had a strong SERS enhancement for deltamethrin determination. The best prediction model was established with partial least squares regression of the SERS spectra ranges of 545~573 cm⁻¹ and 987~1011 cm⁻¹ with a coefficient of determination (R²) of 0.9306, a detection limit of 0.484 mg/L and a residual predictive deviation of 3.046. In summary, this article provides a new rapid and effective method for the detection of pesticide residues in CHMs.

Green Tea Consumption May Be Associated with Cardiovascular Disease Risk and Nonalcoholic Fatty Liver Disease in Type 2 Diabetics: A Cross-Sectional Study in Southeast China

Dietary factors play a crucial role in the management of type 2 diabetes mellitus (T2DM) by reducing cardiovascular disease (CVD) risk. Therefore, we aimed to examine the associations between habitual green tea consumption and risk factors of CVD among T2DM patients. A total of 1013 patients with T2DM were included in a community-based cross-sectional study. Data on dietary habits, including tea consumption, were collected using a food frequency questionnaire. A multivariable logistic regression model was used to analyze the associations. In men, as compared with nongreen tea drinkers, odds ratios (ORs) (95% confidence interval [CI]) of nonalcoholic fatty liver disease (NAFLD) were 2.06 (95% CI, 1.20-3.55) for those with green tea consumption of once per day and 2.45 (95% CI, 1.31-4.58) for more than or equal to twice per day (P-trend = .004); ORs (95% CI) of general obesity were 2.19 (95% CI, 1.02-4.68) and 2.70 (95% CI, 1.18-6.21), respectively (P-trend = .021); whereas no such association was found in women. Sensitivity analysis according to self-awareness of their T2DM status revealed that the positive association between green tea consumption and general obesity was not reliable. Higher intake of green tea was still positively associated with NAFLD, but it only persisted in participants aged ≥52 years or the lower dietary quality subgroup in further analyses. Our findings suggest that tea consumption was associated with an increased risk of NAFLD among male T2DM patients aged 52 years or older, and those with lower dietary quality, which needs to be confirmed in future prospective studies.

Emerging techniques for determining the quality and safety of tea products: A review

Spectroscopic techniques, electrochemical methods, nanozymes, computer vision, and modified chromatographic techniques are the emerging techniques for determining the quality and safety parameters (e.g., physical, chemical, microbiological, and classified parameters, as well as inorganic and organic contaminants) of tea products (such as fresh tea leaves, commercial tea, tea beverage, tea powder, and tea bakery products) effectively. By simplifying the sample preparation, speeding up the detection process, reducing the interference of other substances contained in the sample, and improving the sensitivity and accuracy of the current standard techniques, the abovementioned emerging techniques achieve rapid, cost-effective, and nondestructive or slightly destructive determination of tea products, with some of them providing real-time detection results. Applying these emerging techniques in the whole industry of tea product processing, right from the picking of fresh tea leaves, fermentation of tea leaves, to the sensory evaluation of commercial tea, as well as developing portable devices for real-time and on-site determination of classified and safety parameters (e.g., the geographical origin, grade, and content of contaminants) will not only eliminate the strong dependence on professionals but also help mechanize the production of tea products, which deserves further research. Conducting a review on the application of spectroscopic techniques, electrochemical methods, nanozymes, computer vision, and modifications of chromatographic techniques for quality and safety determination of tea products may serve as guide for other types of foods and beverages, offering potential techniques for their detection and evaluation, which would promote the development of the food industry.

Development and validation of a method for the analysis of five diamide insecticides in edible mushrooms using modified QuEChERS and HPLC-MS/MS

In this study, a new method for simultaneous determination of cyantraniliprole, chlorantraniliprole, tetrachlorantraniliprole, cyclaniliprole and flubendiamide in edible mushrooms by high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) combined with a modified QuEChERS procedure. The samples were extracted using acetonitrile and then cleaned up by primary secondary amine (PSA) and octadecylsilane (C18). The determination of these insecticides was achieved in less than 5 min using an electrospray ionization source in positive mode (ESI+) for cyantraniliprole and chlorantraniliprole, while negative mode (ESI-) for tetrachlorantraniliprole, cyclaniliprole and flubendiamide. The linearities of the calibrations for all target compounds were acceptable (R² ≥ 0.9922). The limits of detection and quantification were 0.05-2 μg kg^-1 and 5 μg kg^-1, respectively. Acceptable recoveries (73.5-110.2%) were acquired for these insecticides with RSDs less than 12.7%. The results demonstrated that the proposed method was effective and convenient for the determination of these insecticides in edible mushrooms.

Recent Trends in the Analysis of Chemical Contaminants in Beverages

Chemical contaminants should not be present in beverages for human consumption, but could eventually be ingested by consumers as they may appear naturally from the environment or be produced by anthropogenic sources. These contaminants could belong to many different chemical sources, including heavy metals, amines, bisphenols, phthalates, pesticides, perfluorinated compounds, inks, ethyl carbamate, and others. It is well known that these hazardous chemicals in beverages can represent a severe threat by the potential risk of generating diseases to humans if no strict quality control is applied during beverages processing. This review compiles the most updated knowledge of the presence of potential contaminants in various types of beverages (both alcoholic and non-alcoholic), as well as in their containers, to prevent undesired migration. Special attention is given to the extraction and pre-concentration techniques applied to these samples, as well as to the analytical techniques necessary for the determination of chemicals with a potential contaminant effect. Finally, an overview of the current legislation is carried out, as well as future trends of research in this field.

A magnetic multi-walled carbon nanotube preparative method for analyzing asymmetric carbon, phosphorus and sulfur atoms of chiral pesticide residues in Chinese herbals by chiral liquid chromatography-quadrupole/linear ion trap mass spectrometry determination

An analytical method for the determination of asymmetric carbon, phosphorus and sulfur atoms in chiral pesticide residues by magnetic multi-walled carbon nanotube sample pretreatment combined with chiral ultra-performance liquid chromatography/quadrupole/linear ion trap mass spectrometry (UPLC-MS/Qtrap) was developed and applied to chiral pesticide residues analysis in Chinese herbals. Eleven different chiral pesticides were found, and 36.4% were positive in Chinese herbals. Three plants containing detectable pesticide residues were observed in Dendrobium nobile, Panax notoginseng flowers and honeysuckle, in the order of decreasing detected concentration. High detection frequencies of 26.1% for (R/S)-(±)-difenoconazole and 14.5% for (R/S)-(±)-metalaxyl and (R/S)-(±)-propiconazole were observed, the residual amount for (R/S)-(±)-difenoconazole, (R/S)-(±)-metalaxyl and (R/S)-(±)-propiconazole were 0.32 ~ 2.5 mg/kg, 0.022 ~ 0.23 mg/kg, 0.62 ~ 3.21 mg/kg respectively. The EF value of (R/S)-(±)-difenoconazole was 0.506 ± 0.046. The EF value of (R/S)-(±)-metalaxyl was lower than 0.5 in Dendrobium nobile, Panax notoginseng flowers, Panax notoginseng roots and hawthorn. The EF of (R/S)-(±)-propiconazole was not significantly enantioselective in honeysuckle and Panax notoginseng flowers. The enantioselectivity of various pesticide residues in different plants cannot be predicted from our existing knowledge and may closely depend on plant growth, environmental conditions or molecular structure.

Magnetic solid-phase extraction based on nano-zeolite imidazolate framework-8-functionalized magnetic graphene oxide for the quantification of residual fungicides in water, honey and fruit juices

In this work, zeolite imidazolate framework-8 (ZIF-8) functionalized magnetic graphene oxide (Fe3O4@APTES-GO/ZIF-8) was successfully synthesized and used as a novel adsorbent in magnetic solid-phase extraction (MSPE) for the determination of four triazole fungicides in water, honey and fruit juices. The main parameters such as extraction time, amount of adsorbent, the pH value of the sample, ionic strength, and desorption solvent which could affect the experiment results were optimization. Under the optimum condition, the obtained linearity of this method ranged from 1 to 1000 µg L-1 for all analytes, with correlation coefficients (R2) ≥ 0.9914. Limit of detections (LODs) and limit of qualifications (LOQs) of four triazole fungicides were ranged from 0.014 to 0.109 µg L-1 and from 0.047 to 0.365 µg L-1, respectively. Based on comparison with outcomes from other studies, Fe3O4@APTES-GO/ZIF-8-MSPE could provide high performance and achieve satisfied results for the analysis of trace triazole fungicides in complicated matrices.

Electrochemical (Bio)Sensors for Pesticides Detection Using Screen-Printed Electrodes

Pesticides are among the most important contaminants in food, leading to important global health problems. While conventional techniques such as high-performance liquid chromatography (HPLC) and mass spectrometry (MS) have traditionally been utilized for the detection of such food contaminants, they are relatively expensive, time-consuming and labor intensive, limiting their use for point-of-care (POC) applications. Electrochemical (bio)sensors are emerging devices meeting such expectations, since they represent reliable, simple, cheap, portable, selective and easy to use analytical tools that can be used outside the laboratories by non-specialized personnel. Screen-printed electrodes (SPEs) stand out from the variety of transducers used in electrochemical (bio)sensing because of their small size, high integration, low cost and ability to measure in few microliters of sample. In this context, in this review article, we summarize and discuss about the use of SPEs as analytical tools in the development of (bio)sensors for pesticides of interest for food control. Finally, aspects related to the analytical performance of the developed (bio)sensors together with prospects for future improvements are discussed.

Preparation of a new three-component deep eutectic solvent and its use as an extraction solvent in dispersive liquid-liquid microextraction of pesticides in green tea and herbal distillates

BACKGROUND

A new solvent, deep eutectic solvent, in which there is growing interest, has been prepared and used as an extraction solvent in the dispersive liquid-liquid method of microextraction. To prepare the solvent, dichloroacetic acid, l-menthol, and n-butanol are mixed at a molar ratio of 4:1:1 and the deep eutectic solvent is formed after heating. Then a dispersive liquid-liquid microextraction method using the prepared solvent is used for the extraction and preconcentration of some pesticides from an aqueous sample. To carry out the procedure, the deep eutectic solvent is mixed with methanol and rapidly injected by a syringe into the aqueous sample containing the analytes. After centrifuging, an aliquot of the sedimented phase is injected into the gas chromatograph. The influence of several variables on the extraction efficiency was investigated and optimized.

RESULTS

Extraction recoveries and enrichment factors were obtained in the ranges of 53-86% and 1760-2853, respectively. The intra- (n = 6) and inter-day (n = 5) precision of the method was satisfactory, with relative standard deviations ≤ 7% obtained at two concentrations of 10 and 50 μg L^-1 of each analyte. Moreover, detection and quantification limits for the target analytes were obtained in the ranges of 0.11-0.23 and 0.38-0.74 μg L^-1 , respectively.

CONCLUSION

Different samples, including green tea, rose water, lemon balm, mint, and pussy willow distillates were analyzed successfully using the method that was developed, and chlorpyrifos was found in rose water at a concentration of 17 ± 1 μg L^-1 (n = 3). © 2019 Society of Chemical Industry.

Dual amplification in a fluorometric acetamiprid assay by using an aptamer, G-quadruplex/hemin DNAzyme, and graphene quantum dots functionalized with D-penicillamine and histidine

D-penicillamine and histidine-functionalized graphene quantum dot (DPA-GQD-His) was synthesized and applied in a fluorometric method for determination of acetamiprid using a G-quadruplex DNAzyme. At first DNA probe (probe 1) consists of a target-specific aptamer with two arms of DNA segments. Probe 1 was hybridized with DNA probe 2 composed of a single DNA sequence with two split G-rich DNA sequences. This leads to the formation of a triplex-to-G-quadruplex (TPGQ). Next, acetamiprid was hybridized with the aptamer in the TPGQ to release free DNA probe 2. The released probe 2, in the presence of of K⁺, undergoes a structural change into a stem-loop structure (by self-complementary hybridization and Hoogsteen hydrogen bonding) that bears a G-quadruplex structure. This is followed by conjugation with hemin to form the G-quadruplex/hemin DNAzyme. The DNAzyme catalyzes the oxidation of o-phenylenediamine by H₂O₂ to produce a yellow fluorescent product with excitation/emission maxima at 420/560 nm. The oxidation product interacts with DPA-GQD-His to achieve a rapid energy transfer between DPA-GQD-His and oxidation product. This increases the fluorescence of the oxidation product and quenches the fluorescence of DPA-GQD-His. DPA-GQD-His also improves the catalytic activity of DNAzyme towards oxidation of ophenylenediamine oxidization and enhances fluorometric response to acetamiprid. The assay works in the 1.0 fM to 1.0 nM acetamiprid concentration range and has a 0.38 fM detection limit. It was successfully applied to the determination of acetamiprid in tea. Graphical abstractThe study reported one double amplification strategy for ultrasensitive fluorescence detection of acetamiprid in tea with D-penicillamine and histidine-functionalized graphene quantum dots and G-quadruplex/heminDNAzyme. The analtyical method exhibits ultra high sensitivity, selectivity and rapidity of fluorescence response to acetamiprid.

Fabrication of sensitive silver-decorated cotton swabs for SERS quantitative detection of mixed pesticide residues in bitter gourds

This study developed a simple, efficient and environmentally friendly fabrication method for surface-enhanced Raman spectroscopy (SERS) wipers for the rapid detection of individual and mixed pesticide residues in actual samples.

Residual behavior and risk assessment of butralin in peanut fields

Butralin is widely used to control single-leaf weeds and some dicotyledons. The application of butralin in the environment may cause residue beyond regulation criteria and residual toxicity. Therefore, it is important to detect and supervise the dissipation behavior of butralin in edible raw food and in the environment. The aim of this study was to monitor butralin in peanuts and soil under farmland conditions and examine the likely dietary risk assessment of butralin for Chinese people on the basis of residual concentrations. A method for the analysis of butralin residue and its dissipation in peanut plants and soil under field conditions was investigated. The results show that an analytical method for the quantization of butralin in peanuts and soil utilizing gas chromatography with electron capture detection (GC-ECD) was developed. Standard recovery experiments using three different butralin spiking levels of 0.01, 0.1, and 1.0 mg kg^-1 in different samples (i.e., peanut kernels, shell, seedling, stalk, and soil) were conducted. The recoveries of butralin from all matrices ranged from 86 to 108% with relative standard deviations from 3 to 6% (n = 5). The limit of quantification (LOQ) of the method was 0.01 mg kg^-1. After storage at - 20 °C for 365 days, the degradation rate of residues of butralin in peanut kernels was less than 30%, which met the storage stability test criteria for pesticide residues in stored commodities of plant origin. The dissipation half-lives of butralin ranged from 4.2 to 6.6 days and 4.6 to 6.6 days in peanut seedlings and soil, respectively, in farmland ecosystems. At the normal harvest time, the final residue concentrations of butralin in peanuts and soil were all below the LOQ. The final total risk quotient (RQ) values were much lower than RQ = 100%, which indicated that the long-run fitness risk associated with butralin residue in different groups of registered crops is correspondingly low for people in China. The current research results could offer guidance for the rational use of butralin and provide data support for the building of maximum residue limits (MRLs) in China.

Pesticides and trace elements in cannabis: Analytical and environmental challenges and opportunities

Cannabis is increasingly used for both medicinal and recreational purposes with an estimate of over 180 million users annually. Canada has recently legalized cannabis use in October 2018, joining several states in the United States of America (e.g., Colorado, California, and Oregon) and a few other countries. A variety of cannabis products including dry flowers, edibles, and oil products are widely consumed. With high demand for cannabis products worldwide, the quality of cannabis and its related products has become a major concern for consumer safety. Various guidelines have been set by different countries to ensure the quality, safety, and efficacy of cannabis products. In general, these guidelines require control of contaminants including pesticides, toxic elements, mycotoxins, and pathogens, as well as residual solvents in regard to cannabis oil. Accordingly, appropriate analytical methods are required to determine these contaminants in cannabis products for quality control. In this review, we focus on the current analytical challenges and method development for detection of pesticides and toxic elements in cannabis to meet various guidelines.

Bio-barcode detection technology and its research applications: A review

With the rapid development of nanotechnology, the bio-barcode assay (BCA), as a new diagnostic tool, has been gradually applied to the detection of protein and nucleic acid targets and small-molecule compounds. BCA has the advantages of high sensitivity, short detection time, simple operation, low cost, good repeatability and good linear relationship between detection results. However, bio-barcode technology is not yet fully formed as a complete detection system, and the detection process in all aspects and stages is unstable. Therefore, studying the optimal reaction conditions, optimizing the experimental steps, exploring the multi-residue detection of small-molecule substances, and preparing immuno-bio-barcode kits are important research directions for the standardization and commercialization of BCA. The main theme of this review was to describe the principle of BCA, provide a comparison of its application, and introduce the single-residue and multi-residue detection of macromolecules and single-residue detection of small molecules. We also compared it with other detection methods, summarized its feasibility and limitations, expecting that with further improvement and development, the technique can be more widely used in the field of stable small-molecule and multi-residue detection.

Chitosan-reduced graphene oxide composites with 3D structures as effective reverse dispersed solid phase extraction adsorbents for pesticides analysis

Chitosan-reduced graphene oxide composites with 3D structures (3D CS-rGO) were prepared via a facile solvothermal synthetic strategy. The reduction of GO and crosslinking of rGO nanosheets with CS into 3D structures were achieved simultaneously in one step. The resulting 3D CS-rGO composite achieves high adsorption capacities of catechins, caffeine and pigments from tea acetonitrile extraction, especially for catechins, which is 10 times higher than that of GO (179.3 mg g^-1vs. 18.7 mg g^-1). The 3D CS-rGO composite exhibits the best removal efficiency of matrix interference in comparison to other traditional adsorbents, which could diminish the matrix effect on targeted pesticides by 1%-55%. A determination method of 70 kinds of pesticides is successfully established for tea based on 3D CS-rGO composite as an efficient reverse dispersed solid phase extraction adsorbent. The established method has the great advantages of operation simplicity, being time saving and high purification performance using only one kind and a low amount of adsorbent. 3D graphene based materials are expected to be promising adsorbents for sample pretreatment in trace contaminant analysis of complex food samples.

A comprehensive analysis of 201 pesticides for different herbal species-ready application using gas chromatography-tandem mass spectrometry coupled with QuEChERs

Developing an analysis of multi-pesticide residues for different herbal species-ready applications is a challenge. In the present work, a comprehensive analysis was proposed for rapid detection of 201 pesticides in various medicinal herbs. Samples were extracted and cleaned up with a high throughput pretreatment approach (modified QuEChERS), and then detected by gas chromatograph coupled to an electron impact ionization triple quadrupole mass spectrometer (GC-EI-MS/MS). The clean-up procedure has been optimized using four types of representative medicinal herbs with different primary or secondary metabolites. Moreover, a mixture of analyte protectants (APs) was to improve the peak shape and intensity of some compounds. The performance of the method was validated according to the European Union SANTE/11813/2017 regulatory guidelines. The limit of quantification (LOQ) was determined to be ≤10 ng mL^-1, and the recovery was between 70.0%-120.0%, with ≤20% RSD for the majority of pesticides. Sixty samples belonging to different species of medicinal herbs (such radix, flos, cortex, fructus, and seeds) were analyzed to evaluate the applicability of the optimized method. High frequency of chlorpyrifos was found in Citri reticulatae pericarpium, Crataegi fructus and Cuscutae semen samples.

Simultaneous Determination of Acrylamide and 5-Hydroxymethylfurfural in Heat-Processed Foods Employing Enhanced Matrix Removal-Lipid as a New Dispersive Solid-Phase Extraction Sorbent Followed by Liquid Chromatography-Tandem Mass Spectrometry

The goal of this study was to develop a method for simultaneous determination of acrylamide (AA) and 5-hydroxymethylfurfural (5-HMF) in heat-processed foods by liquid chromatography-tandem mass spectrometry analysis. Several cleanup methods for the quick, easy, cheap, effective, rugged, and safe (QuEChERS) protocol were investigated and compared: (a) dispersive solid-phase extraction (d-SPE) with Enhanced Matrix Removal-Lipid (EMR-Lipid), (b) d-SPE with primary secondary amine, (c) without the cleanup step, and (d) cleanup with n-hexane. It is the first time that EMR-Lipid sorbent has been used as a d-SPE material to detect AA and 5-HMF in heat-processed foods, and among the four cleanup methods, the EMR-Lipid method provided the best cleanup of co-extracted matrix interferences and the highest extraction efficiency. Validation experiments were carried out for the method using EMR-Lipid as the d-SPE sorbent. Excellent linearity ( R² > 0.999) was achieved, and the limits of detection (LODs) of AA and 5-HMF were 2.5 and 12.5 μg/kg, respectively. The recoveries of AA and 5-HMF levels obtained were in the ranges of 87.3-103.3 and 83.2-104.3%, with precision [relative standard deviations (RSDs)] of 1.2-6.8 and 1.4-7.4% ( n = 3), respectively. The method is accurate and reliable and was successfully applied to analyze the AA and 5-HMF in eight categories of Chinese heat-processed foods.