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

Profiling of pesticides and pesticide transformation products in Chinese herbal teas

Herbal teas have potential health benefits, but they also contain a variety of pesticides and pesticide transformation products (PTPs) that might brings health risks. Our study maps the pesticides and PTPs in two herbal teas (chrysanthemum and Lusterleaf Holly) from two main producing areas in China. Almost all 122 samples contain pesticides, with concentration ranging from 0.0005 to 10.305 mg/kg. Nearly 40% carbendazim and imidacloprid in chrysanthemum teas and λ-cyhalothrin in Lusterleaf Holly have higher concentration levels than the values permitted in EC Regulation No. 396/2005. Distinct distributions of pesticides were found in different teas and production areas. Eight PTPs were identified along with their parents, and were confirmed using a biosynthetic strategy. Acute, chronic and cumulative health risk assessments of pesticides revealed acceptable results. Our study uncovers the profile of pesticides in herbal teas, and provides new insight into discovering the potential environmental pollution and food contaminants.

Dissipative behavior, residual pattern, and risk assessment of four pesticides and their metabolites during tea cultivation, processing and infusion

BACKGROUND

In recent years, metabolic products of pesticides have gained much attention due to their substantial characteristics as organic pollutants. So far, the behavior and metabolite levels of pesticide metabolites in crops have not been characterized well. In the present study, four registered pesticides (imidacloprid, diafenthiuron, malathion and chlorothalonil) were applied on tea plants in Fujian and Sichuan to characterize their metabolites residue pattern and dietary risk.

RESULTS

Four pesticides dissipated first-order kinetics in the fresh tea leaves with the half-lives of 1.4-3.8 days. Nine metabolites were detected in the fresh tea leaves and green tea after processing. The metabolites residues showed an increasing trend first and then declined after treatment, and reached the maximum near the half-lives of pesticide. Compared with the parent pesticide, the total residue and acute risk (included the metabolites) increased by 1.7-105.2 times. Some metabolites, especially those whose parent pesticides have high water solubility and low Log Kow, will be more easily transferred to tea infusion.

CONCLUSION

Pesticides were metabolized rapidly on tea plants after application, but the production of metabolites increased the health risk of tea consumption. These results could provide insights to use the pesticides in tea gardens and risk monitoring after application. © 2022 Society of Chemical Industry.

Commercial yerba mate (Ilex paraguariensis) produced in South America: Determination of dithiocarbamate residues by gas chromatography-mass spectrometry

This work presents an easy and quick miniaturized procedure for the analysis of dithiocarbamates fungicides (DTC), by GC-MS, in yerba mate, an important product in South America. The sample amount, the volume of extracting solvent and acid solution, and the time of hot bath shaking were minimized. A clean-up procedure based on PSA, GCB and MgSO4 was studied in order to improve analytical signal and reduce GC-MS system damage. Blank yerba mate samples were spiked with thiram at equivalent CS₂ concentrations of 0.1, 0.3, 0.5 and 1 mg kg^-1. The validated method at least 2 times faster than the traditional method and was according to the latest European guidelines for pesticide residue analysis. Linearity, limits of detection and quantification, matrix effects, trueness and precision were assessed. Sixty-five commercialized samples from southern Brazil and Argentina were analyzed; 14% of samples presented CS₂ concentration greater than LOQ (0.1 mg kg^-1).

Rapid Screening of 352 Pesticide Residues in Chrysanthemum Flower by Gas Chromatography Coupled to Quadrupole-Orbitrap Mass Spectrometry with Sin-QuEChERS Nanocolumn Extraction

To analyze pesticide residues, GC coupled with quadrupole-Orbitrap MS (GC-Orbitrap-MS) has become a powerful tool because of its unique characteristics of accurate mass full-spectrum acquisition, high resolution, fast acquisition rates, and overcoming matrix interference. This paper presents an efficiency evaluation of GC-Orbitrap-MS for identification and quantitation in the 352 pesticide residues analysis of chrysanthemum flowers in full-scan mode. A streamlined pretreatment approach using one-step extraction and dilution was used, which provided high-throughput processing and excellent recovery. The samples were extracted using acetonitrile. The extracted solution was purified by a Sin-QuEChERS Nano column to suppress the matrix in chrysanthemum flowers and determined by GC-Orbitrap-MS. The calibration curves for the 352 pesticides obtained by GC-Orbitrap-MS were linear in the range of 0.5-200 μg·kg^-1, with the correlation coefficients higher than 0.99. The limits of detection (LODs) and the limits of quantification (LOQs) for the 352 pesticide residues were 0.3-3.0 μg·kg^-1 and 1.0-10.0 μg·kg^-1, respectively. The average recoveries in chrysanthemum flower at three levels were 95.2%, 88.6%, and 95.7%, respectively, with relative standard deviations (RSDs) of 7.1%, 7.5%, and 7.2%, respectively. Lastly, the validated method and retrospective analysis was applied to a total of 200 chrysanthemum flower samples bought in local pharmacies. The proposed method can simultaneously detect multipesticide residues with a good performance in qualitative and quantitative detection.

Monitoring and dietary exposure assessment of pesticide residues in strawberry in Beijing, China

In this study, 142 pesticide residues in 245 strawberry samples, gathered from farmers markets or supermarkets in Beijing from June 2017 to May 2018, were investigated. The samples were analysed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). According to the validation data, including linearity, recovery, precision and measurement uncertainty, the method performed well in monitoring pesticide residues and complied with the requirements of the European Guideline SANTE/11813/2017. Among the strawberry samples, 26.0% contained at least one pesticide residue, four of which contained pesticide residues that exceeded the maximum residue limit of China. Carbendazim, pyrimethanil and azoxystrobin were the most frequently detected pesticides in the strawberry samples. Lower bound, middle bound and upper bound values were used to replace left-censored results. In the worst-case scenario, the hazard index (HI) for adults and children was 0.91% and 3.62%, respectively. Carbofuran, bifenazate and pyraclostrobin were identified as the top three contributors to HI.

Recent Advances in Analytical Methods for Determination of Polyphenols in Tea: A Comprehensive Review

Polyphenols, the most abundant components in tea, determine the quality and health function of tea. The analysis of polyphenols in tea is a topic of increasing interest. However, the complexity of the tea matrix, the wide variety of teas, and the difference in determination purposes puts forward higher requirements for the detection of tea polyphenols. Many efforts have been made to provide a highly sensitive and selective analytical method for the determination and characterization of tea polyphenols. In order to provide new insight for the further development of polyphenols in tea, in the present review we summarize the recent literature for the detection of tea polyphenols from the perspectives of determining total polyphenols and individual polyphenols in tea. There are a variety of methods for the analysis of total tea polyphenols, which range from the traditional titration method, to the widely used spectrophotometry based on the color reaction of Folin–Ciocalteu, and then to the current electrochemical sensor for rapid on-site detection. Additionally, the application of improved liquid chromatography (LC) and high-resolution mass spectrometry (HRMS) were emphasized for the simultaneous determination of multiple polyphenols and the identification of novel polyphenols. Finally, a brief outline of future development trends are discussed.

Elimination of Pendimethalin in Integrated Rice and Procambarus clarkii Breeding Models and Dietary Risk Assessments

This study investigated elimination of the herbicide pendimethalin using an integrated rice and Procambarus clarkii breeding model of indoor and outdoor (pond culture) exposure tests. The pendimethalin levels in 484 samples from the primary rice and P. clarkii integrated breeding areas in Hubei province were monitored, and dietary risk assessments of pendimethalin were calculated. Pendimethalin was quantified using high-performance liquid chromatography tandem mass spectrometry, and detection levels were linear in the range of 1.0 to 10.0 μg/L, and peak areas were positively correlated with concentration, with a correlation coefficient of 0.9996. Recoveries ranged from 86.9 to 103.5%, and the limit of quantitation was 2.5 × 10⁻⁴ μg/L in water, and 1 × 10⁻² μg/kg in tissues, sediments, and waterweeds. The dissipation rate of pendimethalin in tissues and water followed first-order kinetics, with half-lives of 0.51–5.64 d. In 484 samples taken from aquaculture farms, pendimethalin was detected in 8.67% of the samples at levels in the range of 1.95 to 8.26 μg/kg in Hubei province from 2018 to 2020. The maximum residue limit of pendimethalin in P. clarkii has not been established in China, but our dietary risk assessments indicated that consumption of P. clarkii from integrated rice farms was acceptable.

Use of molecular imprinted polymers as sensitive/selective luminescent sensing probes for pesticides/herbicides in water and food samples

As non-biological molecules, molecular imprinted polymers (MIPs) can be made as antibody mimics for the development of luminescence sensors for various targets. The combination of MIPs with nanomaterials is further recognized as a useful option to improve the sensitivity of luminescence sensors. In this work, the recent progresses made in the fabrication of fluorescence, phosphorescence, chemiluminescence, and electrochemiluminescence sensors based on such combination have been reviewed with emphasis on the detection of pesticides/herbicides. Accordingly, the materials that are most feasible for the detection of such targets are recommended based on the MIP technologies.

Highly Sensitive Detection of Carbaryl Pesticides Using Potentiometric Biosensor with Nanocomposite Ag/r-Graphene Oxide/Chitosan Immobilized Acetylcholinesterase Enzyme

Novel, sensitive, selective, efficient and portable electrochemical biosensors are needed to detect residual contaminants of the pesticide 1-naphthyl methylcarbamate (carbaryl) in the environment, food, and essential biological fluids. In this work, a study of nanocomposite-based Ag reduced graphene oxide (rGO) and chitosan (CS) that optimise surface conditions for immobilisation of acetylcholinesterase (AChE) enzyme to improve the performance of catalytic biosensors is examined. The Ag/rGO/CS nanocomposite membrane was used to determine carbaryl pesticide using a potentiometer transducer. The AChE enzyme-based biosensor exhibits a good affinity for acetylthiocholine chloride (ATCl). It can catalyse the hydrolysis of ATCl with a potential value of 197.06 mV, which is then oxidised to produce a detectable and rapid response. Under optimal conditions, the biosensor detected carbaryl pesticide at concentrations in the linear range of 1.0 × 10−8 to 1.0 μg mL−1 with a limit of detection (LoD) of 1.0 × 10−9 μg mL−1. The developed biosensor exhibits a wide working concentration range, detection at low concentrations, high sensitivity, acceptable stability, reproducibility and simple fabrication, thus providing a promising tool for pesticide residue analysis.

Simultaneous detection of ten kinds of insecticide residues in honey and pollen using UPLC-MS/MS with graphene and carbon nanotubes as adsorption and purification materials

An analytical method of simultaneous detection of ten insecticide residues in honey and pollen was established. The samples were purified with QuEChERS approach using new adsorbents and analyzed with UPLC-MS/MS. The results showed that both of graphene and carbon nanotubes were highly efficient adsorbents for the dSPE clean up to eliminate coextractives in the samples, and graphene was superior to carbon nanotubes for the detection of pesticide residues in honey and pollen samples. The proposed method was used to detect pesticide residues in 25 honey samples and 30 pollen samples which were randomly collected from more than ten provinces in China. All honey samples contain 1-27 μg/kg of chlorpyrifos residues. Only 4% of the honey samples were detected containing acetamiprid and imidacloprid, while the other seven pesticides were not detected. Chlorpyrifos residues were found in all pollen samples (5-66 μg/kg), among which twenty percent exceeded the maximum residue limits (MRLs, 50 μg/kg, European Commission Regulation). Most of the pollen samples containing pesticide concentrations higher than MRLs were collected from rape, followed by lotus, camellia, and rose. Besides, 36.7% and 33.3% of the pollen samples had imidacloprid and flupyradifurone higher than 5 μg/kg. A total of 26.7% pollen samples were detected containing bifenthrin, while none of the other six pesticides were detected in pollen samples.

Quantification of 397 pesticide residues in different types of commercial teas: Validation of high accuracy methods and quality assessment

Analytical methods with high sensitivity and accuracy were successfully validated for the quantification of 397 pesticides in different types of tea. For the UPLC-MS/MS method, 191 pesticides of 200 ones in total had "soft" matrix effects and could be quantified by calibration curves in the solvent. For the GC-MS/MS method, matrix-matched calibration curves were established on a mixed blank including white, green, oolong and black organic teas. The method limit of quantifications ranged from 1.0 µg kg^-1 to 10 µg kg^-1 (UPLC-MS/MS) and 1.0 µg kg^-1 to 50 µg kg^-1 (GC-MS/MS), with 70-120% of recovery. These methods was subsequently applied to 106 tea samples from several origins, in which 26 samples contained at least one pesticide violation, with a total of 43 pesticide residue violations. The most frequently detected pesticides were neonicotinoids, synthetic pyrethroids, and triazole fungicides. Taiwan had the most pesticide-contaminated samples followed by China, Vietnam, and India.

Magnetic mesoporous material derived from MIL-88B modified by l-alanine as modified QuEChERS adsorbent for the determination of 6 pesticide residues in 4 vegetables by UPLC-MS/MS

More and more attention has been paid to the improved QuEChERS (quick, easy, cheap, effective, rugged and safe) method in dealing complex sample matrices, especially for the study of QuEChERS adsorbents. In this study, a magnetic mesoporous material, which was derived from MIL-88B modified by l-alanine, was synthesized as modified QuEChERS adsorbents for the simultaneous determination of multiple pesticides (Methomyl, Isoprocarb, Carbofuran, 3-Hydroxycarbofuran, Acetamiprid, Imidacloprid) in Chinese cabbage, celery, long bean and leek. The prepared magnetic adsorbents can effectively remove interfering substances from the sample, and the proposed modified QuEChERS method can reduce sample pretreatment time via an external magnetic field. To achieve the best performance of QuEChERS method, the clean-up time and amount of QuEChERS adsorbents were investigated. Under the optimized conditions, a simple, rapid and sensitive method for the determination of 6 pesticide residues in vegetables was established by coupling the modified QuEChERS to ultrahigh-performance liquid chromatography-tandem mass spectrometry. Excellent sensitivity (The limit of detection for the 6 pesticides ranged from 0.001 to 0.020 µg kg^-1), satisfactory linearity (r² ≥ 0.9952), good recovery (73.9-107.7%) and good precision (3.6-16.9% for intraday relative standard deviation, 0.5-15.0% for interday relative standard deviation) were obtained. Compared with traditional QuEChERS method, the proposed method is simple, cost-effective, and efficient, which indicates that the method can be used to detect carbamate and neonicotinoid pesticides in real samples and provide an excellent pretreatment technique for the detection of trace multi-analytes from complex substrates.

Simultaneous Determination and Health Risk Assessment of Four High Detection Rate Pesticide Residues in Pu'er Tea from Yunnan, China

Four pesticides with a high detection rate in Pu'er tea have been determined by a QuEChERS (quick, easy, cheap, effective, rugged, safe) method with multiwalled carbon nanotubes (MWCNTs), and combined ultrahigh-performance liquid chromatography-triple quadrupole linear ion trap-tandem mass spectrometry (UHPLC-QTRAP-MS/MS). MWCNs have been compared with other common purification materials, and found to be superior. The matrix effect was systematically studied, and the results show that the MWCNs can quickly and effectively reduce matrix interference values, which were in the range from -17.8 to 13.8. The coefficients (R2) were greater than 0.99, with the limit of quantification ranging from 0.1 to 0.5 μg/kg, and the recovery rate ranging from 74.8% to 105.0%, while the relative standard deviation (RSD) ranged from 3.9% to 6.6%. A total of 300 samples, taken from three areas in which Yunnan Pu'er tea was most commonly produced, tested for four pesticides. The results show that the detection rate of tolfenpyrad in Pu'er tea was 35.7%, which is higher than other pesticides, and the lowest was indoxacarb, with 5.2%. The residual concentrations of chlorpyrifos, triazophos, tolfenpyrad and indoxacarb ranged from 1.10 to 5.28, 0.014 to 0.103, 1.02 to 51.8, and 1.07 to 4.89 mg/kg, respectively. By comparing with China's pesticide residue limits in tea (GB 2763-2021), the over standard rates of chlorpyrifos, tolfenpyrad, and indoxacarb were 4.35%, 0.87% and 0%, respectively. The risk assessment result obtained with the hazard quotient (HQ) method shows that the HQ of the four pesticides was far less than one, indicating that the risk is considered acceptable for the four pesticides in Pu'er tea. The largest HQ was found for tolfenpyrad, 0.0135, and the smallest was found for indoxacarb, 0.000757, but more attention should be paid to tolfenpyrad in daily diets in the future, because its detection rate, and residual and residual median were all relatively high.

Construction of a HPLC-SERS hyphenated system for continuous separation and detection based on paper substrates

The HPLC-SERS hyphenated system exhibited the complementary capability of on-line separation and continuous structural identification. It was extended to the application in identifying the illegally added hypoglycemic drugs in the practical dietary supplements.

An aptamer and flower-shaped AuPtRh nanoenzyme-based colorimetric biosensor for the detection of profenofos

A GO grafted SSM was prepared to load the freely mobile capture probe and novel flower-shaped AuPtRh nanospheres were synthesized to be a signal probe, which were constructed to form a colorimetric biosensor for the detection of profenofos.

Human metabolite detection by surface-enhanced Raman spectroscopy

Metabolites are important biomarkers in human body fluids, conveying direct information of cellular activities and physical conditions. Metabolite detection has long been a research hotspot in the field of biology and medicine. Surface-enhanced Raman spectroscopy (SERS), based on the molecular “fingerprint” of Raman spectrum and the enormous signal enhancement (down to a single-molecule level) by plasmonic nanomaterials, has proven to be a novel and powerful tool for metabolite detection. SERS provides favorable properties such as ultra-sensitive, label-free, rapid, specific, and non-destructive detection processes. In this review, we summarized the progress in recent 10 years on SERS-based sensing of endogenous metabolites at the cellular level, in tissues, and in biofluids, as well as drug metabolites in biofluids. We made detailed discussions on the challenges and optimization methods of SERS technique in metabolite detection. The combination of SERS with modern biomedical technology were also anticipated.

N-Acetylcysteine Reverses Monocrotophos Exposure-Induced Hepatic Oxidative Damage via Mitigating Apoptosis, Inflammation and Structural Changes in Rats

Oxidative stress-mediated tissue damage is primarily involved in hepatic injuries and dysfunctioning. Natural antioxidants have been shown to exert hepatoprotective, anti-inflammatory and antiapoptotic properties. The present study evaluated the effect of N-acetylcysteine (NAC) against monocrotophos (MCP) exposure-induced toxicity in the rat liver. Albino Wistar rats were divided into four groups: (1) control, (2) NAC-treated, (3) MCP-exposure, (4) NAC and MCP-coexposure group. The dose of MCP (0.9 mg/kg b.wt) and NAC (200 mg/kg b.wt) were administered orally for 28 days. Exposure to MCP caused a significant increase in lipid peroxidation, protein oxidation and decreased glutathione content along with the depletion of antioxidant enzyme activities. Further MCP exposure increased pro-inflammatory cytokines levels and upregulated Bax and Caspase-3 expressions. MCP exposure also caused an array of structural alternations in liver tissue, as depicted by the histological and electron microscopic analysis. Thepretreatment of NAC improved glutathione content, restored antioxidant enzyme activities, prevented oxidation of lipids and proteins, decreased pro-inflammatory cytokines levels and normalized apoptotic protein expression. Treatment of NAC also prevented histological and ultrastructural alternations. Thus, the study represents the therapeutic efficacy and antioxidant potential of NAC against MCP exposure in the rat liver.

Portable electrochemical biosensor based on laser-induced graphene and MnO2 switch-bridged DNA signal amplification for sensitive detection of pesticide

Developing portable, quantitative, and user-friendly analytical tools for sensitive pesticide assay is of significant importance for guaranteeing food safety. Herein, a novel electrochemical biosensor was constructed by integrating laser-induced graphene (LIG) electrode on polyimide (PI) foil and MnO₂ nanosheets loaded on the paper for point-of-care test (POCT) of organophosphorus (OPs) residues. The principle of this biosensor relied on acetylcholinesterase (AChE)-catalyzed hydrolytic product-triggered disintegration of MnO₂ nanosheets for releasing assistant DNA to initiate nicking enzyme-aided recycling amplification. In the presence of OPs, the activity of AChE was inhibited and could not initiate the cleavage of the electroactive molecules-labeled hairpin probe on the electrode, resulting in the maintenance of the electrochemical response to realize a "sign-on" determination of OPs. The proposed biosensor exhibited satisfactory analytical performance for OPs assay with a linear range from 3 to 4000 ng/mL and a limit of detection down to 1.2 ng/mL. Moreover, the biosensor was useful for evaluating the residual level of pesticides in the vegetables. Therefore, this novel biosensor holds great promise for OPs assay and opens a new avenue on the development of higher-performance POCT device for sensing applications in the environment and food safety fields.

Flowerlike Ni-NiO composite as magnetic solid-phase extraction sorbent for analysis of carbendazim and thiabendazole in edible vegetable oils by liquid chromatography-mass spectrometry

A rapid, selective, and sensitive method was developed for the detection of carbendazim and thiabendazole in edible vegetable oil. Two benzimidazole analytes were pre-concentrated by magnetic solid phase extraction (MSPE) using flowerlike Ni-NiO composite as sorbents and followed by LC-MS/MS analysis. The flowerlike Ni-NiO composite sorbent displayed a high affinity towards benzimidazole analytes due to the reversible coordination interaction between the Ni(Ⅱ) ion and the electron-donating imidazole group. In comparison to the previous methods, this procedure is less time-consuming and simpler during sample preparation. The parameters affecting the extraction efficiency were optimized in detail. The method was validated according to SANTE/12682/2019. The limits of detection were in the range of 0.001-0.003 mg•kg^-1. The recoveries ranged from 89.3% to 110.7% with inter-day and inter-day precision less than 10.9%. The results indicate that flowerlike Ni-NiO composite might be a promising alternative for MSPE of benzimidazole compounds in foods.

Fully Automatic Multi-Class Multi-Residue Analysis of Veterinary Drugs Simultaneously in an Integrated Chip-MS Platform

Microfluidic chip analysis has great potential advantages such as high integration, fast speed analysis, and automatic operation and is widely used not only in biological fields but also in many other analytical areas such as agriculture and food safety. Herein, a fully automatic multi-class multi-residue analysis of veterinary drugs simultaneously in an integrated chip-mass spectrometry (chip-MS) platform was developed. The developed microfluidic chip platform integrated three modules including the extraction and filtration module, "pass-through" clean-up module, and online evaporation module. The resulting chip has been coupled to a MS detector successfully, in which 23 kinds of residues in five classes were simultaneously qualitatively and quantitatively detected without chromatographic separation, obtaining the limits of detection of the spiked milk sample in the range of 0.23-4.13 ng/mL and the recovery rate in the range from 71.7 to 118.0% under optimized conditions. The microfluidic chip system developed in this study provided a new idea for the development of detection chips and exhibited considerable potential in the point-of-care testing in milk.

Determination of new generation amide insecticide residues in complex matrix agricultural food by ultrahigh performance liquid chromatography tandem mass spectrometry

Eight new generation amide insecticide residues analysis by multiwalled carbon nanotubes (MWCNs) cleanup, combined with QuEChERS and ultrahigh performance liquid chromatography tandem mass spectrometry has been developed and successfully applied in complex matrix such as orange, celery, onion, litchi, mango, shallot, chives, avocado, garlic. The matric effect of MWCNs is optimized and compared with ordinary cleanup materials. The results show that the performance of MWCNs is fine and effectively reduce matrix interference. Through chemical structure skeletons analyzed, chlorantraniliprole, bromoantraniliprole, and cyantraniliprole can cause same product ions of m/z 286.0 or 177.1 in the ESI⁺ mode, then tetrachlorantraniliprole and cyclaniliprole can produce collective ions of m/z 146.9 in the ESI^- mode. The coefficients (R²) were greater than 0.9990, the limit of quantification ranges from 0.03 to 0.80 μg/kg, the recovery rate ranges from 71.2 to 120%, and the relative standard deviation (RSD) ranges from 3.8 to 9.4%. The method is fast, simple, sensitive, and suitable for the rapid determination of amide pesticides in complex matrix agricultural food.

Effects and mechanisms of tea on obesity

Obesity has become a global health concern. It increases the risk of several diseases, such as type 2 diabetes mellitus, nonalcoholic fatty liver disease, and certain cancers, which threatens human health and increases social economic burden. As one of the most consumed beverages, tea contains various phytochemicals with potent bioactive properties and health-promoting effects, such as antioxidant, immune-regulation, cardiovascular protection and anticancer. Tea and its components are also considered as potential candidates for anti-obesity. Epidemiological studies indicate that regular consumption of tea is beneficial for reducing body fat. In addition, the experimental studies demonstrate that the potential anti-obesity mechanisms of tea are mainly involved in increasing energy expenditure and lipid catabolism, decreasing nutrient digestion and absorption as well as lipid synthesis, and regulating adipocytes, neuroendocrine system and gut microbiota. Moreover, most of clinical studies illustrate that the intake of green tea could reduce body weight and alleviate the obesity. In this review, we focus on the effect of tea and its components on obesity from epidemiological, experimental, and clinical studies, and discuss their potential mechanisms.

Dissipation of Chlorpyrifos in Bottled Tea Beverages and the Effects of (-)-Epigallocatechin-3-Gallate

ABSTRACT

Bottled tea beverages (BTB) are popular for the health benefits and convenience. Because chlorpyrifos (CP) is commonly used as a biomarker for exposure, as well as a pesticide in the field, it is important to determine the dynamics of CP dissipation in BTB to better perform risk assessments. This study focused on the dynamic behavior of CP for 22 days by fortifying bottled green tea, dark tea, and oolong tea beverages with the parent chemical and analyzing the degradation products. Photoinduction was used to generate the two transient intermediates: the reactive oxygen species from H2O2 and the triplet excited state of CP from the parent chemical in water were designed to observe the effects of (-)-epigallocatechin-3-gallate (EGCG) on the dissipation and transformation of CP. The results indicated that the CP degraded in BTB and the main products were detected. The half-life values of CP illustrated that EGCG increased the dissipation of CP by combination with CP and inhibited the generation of CP-oxon by scavenging the emerged oxidant, the reactive oxygen species, and interfering with the transformation of the triplet excited state of CP. This work suggests EGCG could play various roles in the dissipation and transformation of CP. Thus, a comprehensive identification of CP degradation should be performed when assessing the exposure risk in drinking BTB.

HIGHLIGHTS

Biochar decreased enantioselective uptake of chiral pesticide metalaxyl by lettuce and shifted bacterial community in agricultural soil

A 35-day microcosmic experiment was conducted with lettuce (Lactuca sativa L.) and two metalaxyl (MET) enantiomers (R-MET and S-MET) to understand the roles of biochar in the enantioselective fate of chiral pesticides in soil-plant ecosystems. Wood waste-derived biochar (WBC) amendment effectively decreased the shoot concentrations of R-MET/S-MET and their metabolites R-MET/S-MET acid by 57.7-86.3% and 13.3-32.5%, respectively. The reduced uptake was mainly attributed to the decreased bioavailability of R-MET and S-MET. A lower fraction of R-MET was accumulated by the lettuce in the WBC-amended soils relative to the control, suggesting a decrease in the enantioselective uptake of the chiral pesticide MET in the presence of biochar. Regardless of the WBC amendment, no enantiomerization of MET or MET acid occurred. The application of WBC stimulated soil bacterial diversity, shifted the bacterial community, and enhanced the abundance of pesticide degrading bacteria (e.g., Luteimonas, Methylophilus, and Hydrogenophaga), which were responsible for the enantioselective degradation of MET in the soil. This work expands our understanding of the enantioselective fate of chiral pesticides in the biochar-amended soil ecosystems. These findings can be used to develop biochar-based technologies to remediate soils contaminated with these chiral pesticides to ensure food safety.

Residue pattern of chlorpyrifos and its metabolite in tea from cultivation to consumption

BACKGROUND

Chlorpyrifos (CPF) is a broad-spectrum organophosphorus pesticide widely used to control tea geometrid (Ectropis oblique) and tea green leafhoppers (Empoasca pirisuga Matsumura) in tea trees. The major metabolite of CPF in water, plants, and animals is 3,5,6-trichloro-2-pyridinol, which is more toxic than CPF. However, the dissipation pattern of CPF in tea is unknown.

RESULTS

An optimized QuEChERS sample preparation method combined with ultra-performance liquid chromatography-tandem mass spectrometry was applied to determine the residues of chlorpyrifos and its metabolite in tea during tea planting and green tea processing. During tea planting, the sum of chlorpyrifos and its metabolite dissipated rapidly with a half-life of 1.93 days for tea shoots. The residues of chlorpyrifos and its metabolite in made green tea were 96.89 and 35.88 μg kg^-1 on the seventh day. The values for processing factors of chlorpyrifos and its metabolite were all less than 1, showing that each green tea manufacturing step was responsible for the reduction. The transfer rates of chlorpyrifos and its metabolite from made green tea to its infusion were 0.68-4.62% and 62.93-71.79%, respectively.

CONCLUSION

The risk of chlorpyrifos was negligible to human health based on the hazard quotient, which was 7.4%. This study provides information relevant to the reasonable application of chlorpyrifos in tea planting and is potentially helpful for tea exporting and importing countries to establish harmonized maximum residue limits. © 2020 Society of Chemical Industry.

Nontarget and high-throughput screening of pesticides and metabolites residues in tea using ultra-high-performance liquid chromatography and quadrupole-orbitrap high-resolution mass spectrometry

A Sin-QuEChERS, coupled to UHPLC Q-Exactive Orbitrap MS, was used for nontargeted high-throughput rapid screening and quantitative analysis of residual pesticides and metabolites in green teas. The sample was extracted with 0.1% formic acid in acetonitrile with shaking, salted out and centrifuged, and purified with Sin-QuEChERS Nano solid phase extraction column; with Full MS/ddMS2 as the data collection mode, the database containing 384 pesticides combined with Trace Finder 3.0 software, In the absence of standard products, rapid screening and confirmation of potential pesticide residues in tea samples with accurate mass, isotope abundance ratio, secondary fragment ions, etc. 20 pesticides were used as quality controls to verify the screening method, and the linearity of these pesticides was between 1 and 200 μg/L, and the correlation coefficients were all greater than 0.9922. Moreover, the LOQ was between 0.002 and 0.01 mg/kg. The average recoveries of spiked tea samples were 74%-111%. Efficiency and reliability of this method were investigated by the analysis of 38 Chinese green tea samples. 18 potential residual pesticides were detected by non-targeted screening. The researchers then conducted a quantitative analysis of the 18 potential residual pesticides.

Rapid Screening of 350 Pesticide Residues in Vegetable and Fruit Juices by Multi-Plug Filtration Cleanup Method Combined with Gas Chromatography-Electrostatic Field Orbitrap High Resolution Mass Spectrometry

A new method for screening pesticide residues in vegetable and fruit juices by the multi-plug filtration cleanup (m-PFC) method combined with gas chromatography-electrostatic field orbitrap high resolution mass spectrometry(GC-Orbitrap/MS) was developed. The samples were extracted with acetonitrile, purified with m-PFC and determined by GC-Orbitrap/MS. Qualitative analysis was confirmed by retention time, accurate molecular mass and quantitative analysis were performed with the matrix standard calibration. It could eliminate matrix interference effectively. Eight kinds of typical samples (orange juice, apple juice, grape juice, strawberry juice, celery juice, carrot juice, cucumber juice, tomato juice) were evaluated. The linear ranges of the 350 pesticides were from 5 to 500 μg/kg, with good correlation coefficients greater than 0.990. The limits of detection (LODs) were 0.3-3.0 μg/kg and the limits of quantification (LOQs) were 1.0-10.0 μg/kg. The average recoveries at three spiked levels of 10, 100, 200 μg/kg were in the range of 72.8-122.4%, with relative standard deviations (RSDs) of 2.0-10.8%. The method has effectively improved the determination efficiency of pesticide residue screening by high-resolution mass spectrometry in vegetable and fruit juices.

1-Octyl-3-methylimidazolium hexafluorophosphate-functionalised magnetic poly β-cyclodextrin for magnetic solid-phase extraction ofpyrethroids from tea infusions

In this study, a novel sorbent, 1-octyl-3-methylimidazolium hexafluorophosphate functionalised magnetic poly β-cyclodextrin, was successfully synthesised and applied to magnetic solid-phase extraction for the determination of pyrethroids in tea infusions. The sorbent was characterised by transmission electron microscopy, energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, vibrating sample magnetometer and Brunauer-Emmett-Teller measurement. All factors affecting extraction efficiency, such as sorbent amount, extraction time, ionic strength and desorption conditions, were optimised individually. Under the chosen conditions, wide linearity (2.5-500 μg L^-1) with determination coefficients ranging from 0.9995 to 0.9999, low limits of detection of 0.32-0.54 μg L^-1 and good precision (intra-day: 2.6-7.0%; inter-day: 3.5-7.6%) were achieved for four pyrethroids in tea infusions. The relative recoveries of target analytes in real tea infusion samples were from 70% to 101% with relative standard deviations lower than 9.1%. We conclude that the proposed method is promising in the detection of pyrethroids in tea infusions.

Simultaneous determination of 14 pesticide residues in tea by multi-plug filtration cleanup combined with LC-MS/MS

A combined method of multi-plug filtration cleanup (m-PFC) and liquid chromatography-triple quadrupole mass spectrometry (LC-MS/MS) was established to simultaneously detect 14 pesticides in tea. The pesticides in water-soaked tea were extracted with acetonitrile. Cleanup of tea extract was performed using an m-PFC column packed with multiple cleanup materials: multi-walled carbon nano-tubes (MWCNTs), primary secondary amine (PSA) and anhydrous magnesium sulfate (MgSO₄). The cleanup effect of the column was evaluated based on the rates of removal of tea components that interfered with pesticide recovery, henceforth referred to as interference components. Results showed that 14 pesticides had strong linearity in the range of 5-500 μg L^-1 (r² > 0.99). The quantitative limits were within the range of 3-50 μg kg^-1. The average recoveries of 14 pesticides spiked into three different blank tea samples (green tea, black tea, oolong tea) at three levels of 0.05, 0.50 and 2.00 mg kg^-1 were in the range of 62.3-108.8% with relative standard deviations of 0.2-13.6%. The m-PFC method can greatly improve the efficiency of sample pretreatment. Furthermore, this work provides methodological guidance on how to select cleanup materials and allocate their proportions.

Green tea protects against hippocampal neuronal apoptosis in diabetic encephalopathy by inhibiting JNK/MLCK signaling

Although diabetic encephalopathy (DE) is a major late complication of diabetes, the pathophysiology of postural instability in DE remains poorly understood. Prior studies have suggested that neuronal apoptosis is closely associated with cognitive function, but the mechanism remains to be elucidated. Green tea, which is a non-fermented tea, contains a number of tea polyphenols, alkaloids, amino acids, polysaccharides and other components. Some studies have found that drinking green tea can reduce the incidence of neurodegenerative diseases and improve cognitive dysfunction. We previously found that myosin light chain kinase (MLCK) regulates apoptosis in high glucose-induced hippocampal neurons. In neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease, activation of the JNK signaling pathway promotes neuronal apoptosis. However, the relationship between JNK and MLCK remains to be elucidated. Green tea serum was obtained using seropharmacological methods and applied to hippocampal neurons. In addition, a type 1 diabetes rat model was established and green tea extract was administered, and the Morris water maze test, Cell Counting Kit-8 assays, flow cytometry, western blotting and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling assays were used to examine the effects of green tea on hippocampal neuronal apoptosis in diabetic rats. The results demonstrated that green tea can protect against hippocampal neuronal apoptosis by inhibiting the JNK/MLCK pathway and ultimately improves cognitive function in diabetic rats. The present study provided novel insights into the neuroprotective effects of green tea.

In situ reduction triggers the highly sensitive detection of pesticide by classic gold nanoparticle and quantum dots nanocomposite

Fluorescence "turn on" method is always preferable for target detection under the urgent demand to develop point-of-care portable sensors in practical applications due to its higher selectivity and less false positives. However, there is only few reports of pesticide monitoring based on this strategy so far most probably ascribed to its poor hydrophilicity and reactivity. In this work, triggered by reductant tris (2-carboxyethyl) phosphine hydrochloride (TCEP), initially fluorescence-quenched gold nanoparticles (Au NPs)-decorated quantum dots (QDs)-embedded nanobead shows obvious fluorescence "turn on" signal response to thiram with concentration response range of 0.01-20 μM and limit of detection (LOD) of 7 nM due to the target-induced dissociation of Au NPs from the surface of probe nanobead. Moreover, paper sensor has been successfully developed by immersing commercial drainage membrane in probe solution for visual detection of thiram with the ultrahigh LOD (50 nM) by the naked eye. More importantly, this work, for the first time, reported an in situ reduction strategy to improve the interaction between target and nanoprobe and thus bring obvious signal output for pesticide detection with high sensitivity, demonstrating the potential to expand the detection scope of nanomaterials.

Determination and dietary risk assessment of 284 pesticide residues in local fruit cultivars in Shanghai, China

The presence of pesticide residues has become one of the main risk factors affecting the safety and quality of agro-food. In this study, a multi-residue method for the analysis of 284 pesticides in five local fruit cultivars in Shanghai was developed based on ultrahigh-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QTOF/MS). The limits of determination and the limits of quantitation of pesticides were 0.6–10 and 2–30 μg/kg, respectively. A total of 44, 10, 10, 18, and 7 pesticides were detected in strawberries, watermelons, melons, peaches, and grapes, respectively. The pesticide levels in 95.0% of the samples were below the maximum residual limits (MRLs) prescribed by China, and in 66.2% of the samples below the EU MRLs. The dietary risk assessment study showed big differences in the chronic and acute exposure risk values among different Chinese consumer groups. Through fruit consumption, children/females showed higher exposure risks than adults/males. But both the risk values were less than 100%, indicating that potential dietary risk induced by the pesticides was not significant for Chinese consumers. Nevertheless, certain measures are needed for both growers and the government in order to decrease the MRL-exceeding rate of pesticide residues and ensure the quality and safety of fruits for consumers.

[Screening and confirmation of 244 pesticide residues in chilli by gas chromatography-quadrupole time-of-flight mass spectrometry]

QuEChERS pretreatment combined with gas chromatography-quadrupole time-of-flight mass spectrometry (GC-Q-TOF/MS) has been investigated for application in screening 244 pesticide residues in chilli. Fresh chilli samples were extracted with acetonitrile, and dried chilli samples were extracted using an acetonitrile/acetic acid (99∶1, v/v) mixture. The two extraction solvents were stored at -20 ℃. After salting out and cleaning by dispersive solid phase extraction (dSPE), heptachlor epoxide B was added as an internal standard, and the resulting residues were dissolved in 1.00 mL acetone. The dissolved sample solution was loaded onto an HP-5MS UI column (30 m×0.25 mm, 0.25 μm) and eluted by GC-Q-TOF/MS with a programmable temperature vaporizer and splitless injection in the full-scan mode. The compensation effects of the analytical protectant (AP) and matrix-matched calibration method on the matrix effect were established. AP could be used in the fresh chilli matrix to compensate for matrix effects, but it was not effective in the dried chilli matrix. The matrix-matched calibration method was effective in both matrices, which was selected for the quantification of pesticide residues in the samples. Because of the existence of the isomers of one compound and the same characteristic ions of different compounds, analyte detection was based on a flexible retention time deviation of ±0.25 min and accurate mass deviation of ±20×10 -6. Screening was performed by the software in the automatic matching mode. Compound identification and quantitation were based on a database and calibration curve established with reference materials. Suspicious samples were subjected to manual analysis. Quantitative analysis of 244 pesticide residues in fresh chilli and 222 pesticide residues in dried chilli was performed. The results showed that the developed database and method can provide a reference for the high-throughput screening and quantitation of fresh and dried chilli. Different levels of pesticides were added to the blank chilli samples, and the addition level corresponding to a signal-to-noise ratio (S/N) of 10 was used as the limit of quantification (LOQ). The LOQs of 44 pesticides with a maximum residue limit (MRL) ≤0.05 mg/kg in fresh chilli did not exceed 0.010 mg/kg. The linear ranges of these 44 pesticides were 0.01-1.00 mg/L. At spiked levels of the LOQ and 2.5 times the LOQ, the ratios of the 44 pesticides with recoveries of 60% to 120% were 88.64% and 100%, respectively. The LOQs of 200 pesticides with MRLs ≥0.05 mg/kg or without MRLs in fresh chilli did not exceed 0.025 mg/kg. The linear ranges of these 200 pesticides were 0.05-1.00. At spiked levels of the LOQ, twice the LOQ, and 10 times the LOQ, the ratios of the 200 pesticides with recoveries of 60% to 120% were 49.50%, 87.00%, and 89.50%, respectively. The linear correlation coefficients (r 2) of the 244 pesticides in fresh chilli were greater than 0.99. The LOQs of 222 pesticides in dried chilli were less than 0.15 mg/kg, and the linear ranges were 0.04-1.00 mg/L. The ratios of these 222 pesticides with r 2 greater than 0.99 was 95.46%. At spiked levels of the LOQ, twice the LOQ and 10 times the LOQ in dried chilli, the ratio of the 222 pesticides with recoveries of 60% to 120% were 72.52%, 73.42%, and 81.53%, respectively. The established screening and confirmation method was used to analyze 12 fresh chilli samples and 14 dried chilli samples. Eight pesticides were found in nine fresh chilli samples and three dried chilli samples, all of which were confirmed to be positive after manual identification. The concentrations of these pesticides were lower than the MRLs required by GB 2763-2019: National Food Safety Standard Maximum Residue Limits for Pesticides in Food. The results demonstrate that the established method is rapid, easy to execute, efficient, and reliable. It can be used for the high-throughput screening and quantitation of pesticide residues in fresh and dried chilli.

Fabrication of Nano/Micro-Structured Electrospun Detection Card for the Detection of Pesticide Residues

A novel nano/micro-structured pesticide detection card was developed by combining electrospinning and hydrophilic modification, and its feasibility for detecting different pesticides was investigated. Here, the plain and hydrophilic-modified poly(ε-caprolactone) (PCL) fiber mats were used for the absorption of indolyl acetate and acetylcholinesterase (AChE), respectively. By pre-treating the fiber mat with ethanol, its surface wettability was improved, thus, promoting the hydrolysis of the PCL fiber mat. Furthermore, the absorption efficiency of AChE was improved by almost two times due to the increased hydrophilicity of the modified fiber mat. Noteworthily, this self-made detection card showed a 5-fold, 2-fold, and 1.5-fold reduction of the minimum detectable concentration for carbofuran, malathion, and trichlorfon, respectively, compared to the national standard values. Additionally, it also exhibited good stability when stored at 4 °C and room temperature. The food detection test showed that this nano/micro-based detection card had better detectability than the commercial detection card. Therefore, this study offers new insights into the design of pesticide detection cards, which also broadens the application of electrospinning technique.

Rapid detection of chlorpyrifos pesticide residue in tea using surface-enhanced Raman spectroscopy combined with chemometrics

Surface enhanced Raman spectroscopy based on rapid pretreatment combined with Chemometrics was used to determine chlorpyrifos residue in tea. Au nanoparticles were used to as enhance substrate. Different dosages of PSA and NBC were investigated to eliminate the tea substrate influence. Competitive adaptive reweighted sampling (CARS) was used to optimize the characteristic peaks, and compared to full spectra variables and the experiment selected variables. The results showed that PSA of 80 mg and NBC of 20 mg was an excellent approach for rapid detecting. CARS - PLS had better accuracy and stability using only 1.7% of full spectra variables. SVM model achieved better performance with R²_p = 0.981, RMSEP = 1.42 and RPD = 6.78. Recoveries for five unknown concentration samples were 98.47 ~ 105.18% with RSD - 1.53% ~ 5.18%. T-test results showed that t value was 0.720, less than t0.05,4 = 2.776, demonstrating that no clear difference between the real value and predicted value. The detection time of a single sample is completed within 15 min. This study demonstrated that SERS coupled with Chemometrics and QuEChERS may be employed to rapidly examine the chlorpyrifos residue in tea towards its quality and safety monitoring.

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.

Determination of multi pesticide residues in leaf and needle samples using a modified QuEChERS approach and gas chromatography-tandem mass spectrometry

In order to gain a better insight into pesticide and pollutant exposure in forests, a rapid and sensitive gas chromatography-tandem mass spectrometry (GC-MS/MS) method for the determination of 208 pesticide residues in leaves and needles has been established. The modified QuEChERS (quick, easy, cheap, effective, rugged and safe) approach uses 2 g of homogenized sample, acetonitrile and water as extraction agents, combined with citrate buffer for the following salting out step. The limits of quantification (LOQs) were determined to 0.0025-0.05 mg kg-1, respectively. Calibration curves showed a linear range between the respective LOQ and 1.0 mg kg-1 with coefficients of determination (R2) ≥ 0.99 for all analyzed pesticides. The recovery rates ranged from 69.7% to 92.0% with a relative standard deviation below 20%. The analysis of beech leaves, spruce and pine needles (each n = 3) provided a proof of concept for the developed methodology and revealed the presence of six pesticide residues (boscalid, epoxiconazole, fenpropimorph, lindane, terbuthylazine, terbuthylazine-desethyl). The results underline the strong need for systematic surveillance of the uncontrollable exposure of pesticides to nature.

One step extraction followed by HPLC-ESI-MS/MS for multi-residue analysis of diacylhydrazine insecticides in water, sediment, and aquatic products

A multi-residue analysis of six diacylhydrazine insecticides in water, sediment, and aquatic products was established by liquid chromatography triple quadrupole tandem mass spectrometry (LC-MS/MS). The water sample was extracted with acetonitrile by low-temperature enrichment liquid-liquid extraction technology. The sediment and aquatic products were prepared using QuEChERS technique. Method validation showed perfect linearity with correlation coefficients (R) more than 0.9992 for all insecticides, and the matrix effects were nearly negligible (-1.42% to -0.27%) for water, sediment and aquatic products. The recoveries were 80.0-99.7% at three spiked levels (0.02 ng·mL^-1, 0.1 ng·mL^-1, 0.5 ng·mL^-1; 2.0, 10, and 50 ng·g^-1) and the precisions (intra-day and inter-day precision) were lower than 5.28%, with the low LODs (3.8 ~ 9.6 pg·mL^-1; 0.38-0.96 ng·g^-1) and LOQs (12.7 ~ 32.0 pg·mL^-1; 1.27-3.20 ng·g^-1) for water, sediment, and aquatic products, indicating the good accuracy and precision of the proposed method. The applicability, efficiency, and sensitivity of this method have been proved in the analysis of six diacylhydrazine insecticides in water, sediment, and crucian carp in Rice- crucian carp - integrated planting system.

Simultaneous multi-determination of pesticide residues in black tea leaves and infusion: a risk assessment study

This study aimed to investigate the concentration of 33 pesticide residues in 60 black tea samples collected from Iran, determine their transfer rate, and assess their health risk during brewing. Pesticide extraction and analysis were performed by using a quick, easy, cheap, effective, rugged, and safe (QuEChERS) method and gas chromatography/tandem mass spectrometry (GC-MS/MS), respectively. The limits of detection (LOD) and the limits of quantification (LOQ) of pesticides were ranged 0.1-7.26 and 0.8-24 μg/kg for dried tea leaves and 0.03-3.1 and 0.09-10 μg/L for the tea infusion, respectively. The levels of pesticide residue in 52 (86.67%) out of 60 tea samples were above the LOD (0.1-7.26 μg/kg). Twenty four (40%) of the samples contained pesticides in a concentration higher than the maximum residue limit (MRL) set by the European Commission (EC). Seven out of 33 validated pesticides were detected in dried tea leaf samples that only four of seven, including buprofezin, chlorpyrifos, hexaconazole, and triflumizole, were transferred into tea infusion, demonstrating that the concentrations of pesticides in infusion were raised during brewing. The risk assessment study for detected pesticides in the tea infusion samples indicated that this beverage consumption was safe for consumers, while the mean residue of some pesticides in positive samples was higher than the MRL; therefore, periodic control of these pesticides should be regularly implemented.

Collaborative compounding of metal-organic frameworks for dispersive solid-phase extraction HPLC-MS/MS determination of tetracyclines in honey

Metal-organic frameworks (MOFs), a sort of dispersive solid-phase extraction (d-SPE) material, has shown considerable prospects in the pretreatment of food, biological and other complex samples. Herein, we developed a method for compounding MOFs for d-SPE and trace determination of tetracyclines (TCs) in honey. When the compounding ratio of MIL-101 (Cr), MIL-100 (Fe) and MIL-53 (Al) was 7:1:2, adsorption-extraction was effective. Followed by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), the limits of detection were 0.073-0.435 ng/g and the limits of quantitation ranged from 0.239 to 1.449 ng/g for oxytetracycline, tetracycline, chlortetracycline and doxycycline. The method was applied to four kinds of honey samples with recoveries from 88.1% to 126.2%. The compounding of MOFs provides a strategy for purification and multi-target extraction from complex food matrices by d-SPE.

Portable and quantitative detection of carbendazim based on the readout of a thermometer

The detection of carbendazim (CBZ) is important for food safety and human health. However, most current analytical methods require large instruments and highly trained operators. In order to solve this problem, herein, an innovative portable and quantitative photothermal assay platform relying on a thermometer readout for the detection of CBZ has been developed. Gold nanoparticles (AuNPs), which exhibit a strong distance-dependent photothermal effect under specific laser irradiation, were utilized as indicators. The CBZ aptamer was introduced to protect AuNPs from salt-mediated aggregation. When CBZ is present, the binding event between CBZ and aptamer leads to the loss of the aptamer protective effect on AuNPs, and AuNP aggregation occurs. Under 650-nm laser irradiation, the increase in temperature associated with an AuNP-dependent photothermal effect is highly related to the CBZ concentration. Having the advantages of user-friendliness, low cost, quick response, and portability, this method has great potential for on-site applications.