A novel method based on MSPD for simultaneous determination of 16 pesticide residues in tea by LC–MS/MS

Simultaneous Screening and Quantification of 479 Pesticides in Green Tea by LC-QTOF-MS

A high-throughput screening and quantification method for 479 pesticides in green tea was established based on solid-phase extraction combined with liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). Pesticides were extracted from samples using an optimized SPE (TPT cartridges) procedure. LC-QTOF-MS in All Ions MS/MS scan mode acquired full MS data for quantification and product ion spectra for identification. LC-QTOF-MS quantification was achieved using matrix-matched standard calibration curves to achieve the optimal method accuracy. The method performance characteristics included the linearity, overall recovery, precision, and measurement uncertainty being evaluated. The validation results exhibited a good sensitivity with the LOQs of 5-55 µg/kg, which was satisfactory for their MRLs in China or the EU. The recoveries of more than 92.7% of the 479 pesticides in green tea were 70-120% at the three spiked levels with a precision of ≤20%. Finally, this method was employed to analyze 479 pesticides in 95 tea samples from markets in China. The test results of the tea samples showed that tolfenpyrad, buprofezin, and pyridaben were found with lower concentrations. The method has effectively improved the determination efficiency of pesticide residue screening by high-resolution mass spectrometry in green tea.

Comparison of Four Different Polymeric Adsorbents as Clean-up Agents for Pesticide Analysis in Tea with LC MS/MS

Previously published studies indicate that tea (Camellia sinensis) contains essential oils, flavonoids, phenolics, lipids, natural pigments, sugars, and oligosaccharides. These essential biomolecules in Camellia sinensis cause serious problems in the determination of pesticide residues. High amount of co extractives can exhibit chromatographic characteristics similar to some pesticides, which may cause serious matrix effects and significant interference in mass spectrometry analysis. In this study, we compared four polymeric resins as clean-up sorbents for the determination of 216 pesticide residues in tea by a high performance liquid chromatography triple quadrupole mass spectrometry. styrene-divynilbenzene  (Diaion HP20), Polyamide 6, Polyvinylpolypyrrolidone (PPVP), and Amberlite XAD 7 were used as clean-up sorbents instead of PSA. However,to evaluate the effectiveness of the adsorbents, recovery studies were carried out using these adsorbents. In addition, GC-MS analysis was also performed to see the ability of these adsorbents to remove co-extracts. According to the recovery results, when the acceptable limit was accepted as 60-140%, it was determined that the resin that gave the best results with 170 pesticides was polyamide. Diaion was the second resin with 166 pesticides, while XAD, PSA which was used as control group and PPVP were determined as the third, fourth, and fifth resins with very close values of 159, 155, and 152 pesticides, respectively. According to GC-MS total ion analysis, it was observed that PSA gave the chromatogram with the least co- extract, while it was observed that PSA was the worst adsorbent in removing caffeine, one of the main bioactive compounds in tea. XAD-7 and Polyamide were found to be the best adsorbents in removing caffeine.

The toxicokinetics and risk assessment of pyrethroids pesticide in tilapia (Oreochromis mossambicus) upon short-term water exposure

Pyrethroids pesticides (PPs) are the widely adopted synthetic pesticides for agriculture and fishery. The frequent use of these pesticides leads to the accumulation of residues in the freshwater environments in China, subsequently affecting aquatic organisms and ecosystems. However, there are few reports on the toxicological and risk assessment of aquaculture aquatic products. In this study, the uptake, depuration kinetics and potential risk to human health and ecology of fenpropathrin, cypermethrin, fenvalerate, and deltamethrin were assessed using tilapia. The results indicated that four PPs were readily accumulated by tilapia. The bioconcentration factors (BCF) of the PPs in plasma and muscle were between 71.3 and 2112.1 L/kg and 23.9-295.3 L/kg, respectively. The half-lives (t_1/2) of muscle and plasma were 2.90-9.20 d and 2.57-8.15 d. The risks of PPs residues in the muscle of tilapia and exposed water were evaluated by hazard quotient (HQ) and risk quotient (RQ). Although PPs residues in tilapia had a low dietary risk to human health, the residues in the exposed water had a high ecological risk to fish, daphnia, and green algae. Therefore, assessing the PPs content in freshwater aquaculture and monitoring their dosages and frequencies are highly necessitated to avoid their adverse effect on the aquaculture environment.

Rapid and non-invasive surface-enhanced Raman spectroscopy (SERS) detection of chlorpyrifos in fruits using disposable paper-based substrates charged with gold nanoparticle/halloysite nanotube composites

Chlorpyrifos is one of the most widely used organophosphate insecticides in agricultural production. Nevertheless, the residues of chlorpyrifos in agricultural by-product seriously threaten human health. Thus, the ultrasensitive detection of chlorpyrifos residues in agri-food products is of great demand. Herein, an AuNP/HNT-assembled disposable paper SERS substrate was prepared by an electrostatic self-assembly method to detect chlorpyrifos residues. The AuNP/HNT paper substrate exhibited high SERS activity, good reproducibility, and long-term stability, which was successfully used for quantitative detection of chlorpyrifos; the detection limit reached 7.9 × 10^-9 M. For spiked apple samples the calculated recovery was 87.9% with a RSD value of 6.1%. The excellent detection ability of AuNP/HNT paper-based SERS substrate indicated that it will play an important role in pesticide detection in the future. AuNP/HNT assembled disposable paper SERS substrate was prepared by an electrostatic self-assembly method to detect chlorpyrifos residues in fruits.

Chromatographic techniques for the analysis of organophosphate pesticides with their extraction approach: a review (2015-2020)

In agriculture, a wide range of OPPs has been employed to boost crop yield, quality, and storage life. However, due to the ever-increasing population and rapid urbanization, pesticide use has surged in recent years. These compounds are exceedingly poisonous to humans, and despite the fact that specific legislation prohibits their use, the frequency of toxic and/or fatal incidents, as well as current statistics, suggest that they are currently accessible. As a result, determining the exposure to these substances as well as their detection (and that of their metabolites) in different types of exposed samples has become a hot issue in terms of quality and safety concerns. However, developing tools for the evaluation of these substances is a critical challenge for laboratories. Various chromatographic-based methods reported in the period of 2015-2020 have been developed, which are summarized and critically reviewed in this article, including the extraction of the target OPPs from different kinds of matrices. A comparison among the extraction and analysis techniques has been made in the current review article.

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.

A global systematic review, meta-analysis and health risk assessment on the quantity of Malathion, Diazinon and Chlorpyrifos in Vegetables

It is widely believed that an increasing trend in the production and consumption of vegetables has led to a dramatic rise in the use of pesticides potentially threatening the health of consumers around the world. This systematic study along with meta-analysis has mainly centered on the evaluation of the quantity of three well-known pesticides namely, Malathion (MLT), Diazinon (DZN) and Chlorpyrifos (CPF) in vegetables. In this regard, a comprehensive literature search has been performed over the last decade (January 1, 2011 to June 21, 2020) within the scientific databases including PubMed, Web of Science, and Scopus. Of 1239 articles identified through the database screening, 22 plus 37 data report were retained and included in the meta-analysis phase. Additionally, the probabilistic human health risks for the consumers due to the intake of CPF, DZN and MLT from eating vegetables were estimated by the Monte Carlo Simulated (MCS) method. According to the findings, the maximum quantities of MLT, DZN and CPF in the vegetables were observed in Pakistan (222 μg/kg, 95%CI = 214.94-229.08), Thailand (245.00, 95% CI = 235.2-254.8) and South Korea (440 μg/kg, 95% CI = 437.19-442.81), while the lowest concentration levels were reported in China (1.7 μg/kg, 95% CI = 1.56-1.84), Poland (0.57, 95% CI = 0.46-0.68) and Poland (5.78 μg/kg, 95% CI = 4.40-7.12), respectively. The results of the Egger's and the Begg's tests revealed that no bias with regard to the potential publication was observed. Finally, non-carcinogenic risk assessment results demonstrated that the exposure to the studied pesticides thorough vegetables consumption could not threaten the health of consumers.

pH-Response Quantum Dots with Orange-Red Emission for Monitoring the Residue, Distribution, and Variation of an Organophosphorus Pesticide in an Agricultural Crop

Development of simple, sensitive, and reliable fluorescence sensors for monitoring the residue, distribution, and variation of organophosphorus pesticides (OPs) in agricultural crops is highly urgent but remains challenging, which is ascribed to deprivation of an ideal fluorophore and ingenious detection strategy. Herein, we report the fabrication of cadmium telluride quantum dots (CdTe QDs) with bright emission, good water dispersion, and long emission wavelength for OP screening based on the unique response of CdTe QDs to pH and the inhibition of OPs on acetylcholinesterase (AChE) activity. AChE catalyzed hydrolysis of acetylcholine (ACh) into CH₃COOH, which protonated CdTe QDs to decline the fluorescence, whereas target OP impeded AChE from catalyzing hydrolysis of ACh into CH₃COOH, making little influence in fluorescence of CdTe QDs. On the basis of the change in fluorescence, sensitive detection of OP was acquired, with the limit of detection at 0.027 ng/mL, which was comparable or lower than that of most known OP sensors. Furthermore, the CdTe-QD-based sensor was successfully applied for precisely monitoring the residue, distribution, and variation of methidathion in Chinese cabbage and cultivated soil. Therefore, the proposed sensor was anticipated to supply a promising alternative for food safety guarantee and was an valuable application for OP screening.

Human health risk assessment of pesticide residues in honeysuckle samples from different planting bases in China

The buds and initial flowers of honeysuckle (Lonicera japonica Thunb.) are most widely used in traditional Chinese medicines (TCMs). In recent years, the problem of pesticide residues in honeysuckle has attracted much attention. This research aimed to study pesticide residual situation of honeysuckle in China and estimate the potential health risks for consumers using the HQ (hazard quotient) and HI (hazard index) methods. A reliable and robust method was established to determine and quantify 137 pesticide residues simultaneously by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) for 151 honeysuckle samples from different planting bases in China in 2017 and 2018. Fifty-four pesticides were detected in total, including 10 unauthorized pesticides (chlorpyrifos, fipronil, carbofuran, omethoate, isofenphos-methyl, triazophos, methomyl, dimethoate, methidathion, and methamidophos). One hundred and fifty (99.3%) samples contained at least 1 and up to 31 pesticides and/or their metabolites, with concentrations ranging from 0.001 to 3.087 mg/kg. Carbendazim, chlorbenzuron, imidacloprid, chlorpyrifos, and acetamiprid were the most frequently detected pesticides in 2017 and 2018, and the corresponding detection rates were 95.31%, 64.06%, 65.63%, 53.13%, 57.81%, and 98.85%, 88.51%, 70.11%, 77.01%, 57.47%, respectively. The acute hazard quotient (HQ_a) of carbofuran was 1.54 for specific population (fetus, infants, and pregnant or nursing women), which indicated that it posed a potential acute health risk. In the cumulative risk assessment, the acute hazard index (HI_a) of insecticides in honesuckle for children and the specific population were 1.34 and 3.36, respectively, suggesting that they posed potential acute cumulative health risks. These results were of theoretical and practical value for evaluating the safety of honeysuckle and improving its quality and safety.

Double-enzymes-mediated Fe2+/Fe3+ conversion as magnetic relaxation switch for pesticide residues sensing

It is a great challenge to develop a newly rapid and accurate detection method for pesticide residues. In this work, based on acetylcholinesterase (AChE) and choline oxidase (CHO), a double-enzymes-mediated Fe²⁺/Fe³⁺ conversion as magnetic relaxation switch was explored for the measurement of acetamiprid residue. In the double-enzymes reactions, acetylcholine chloride (ACh) can be catalyzed to produce choline by AChE, which is successively hydrolyzed to betaine and hydrogen peroxide (H₂O₂) by CHO. According to the enzyme inhibition principle, AChE activity will be inactivated in the presence of acetamiprid, thus leading to the less production of H₂O₂. Wherein, Fe²⁺, ACh, AChE and CHO were optimized as the reaction substrates. In the reaction system, acetamiprid can be reflected by the transverse relaxation time (T₂) that related with H₂O₂ mediated Fe²⁺ variations, which was further developed as an enzyme cascade amplification method. The detection linear range is 0.01∼1000 μg mL^-1 (R² = 0.99), and the limit of detection (LOD) is 2.66 ng mL^-1 (S/N = 3, n = 3), behaving a 335-fold improvement in LOD than that of traditional enzyme inhibition method (0.89 μg mL^-1). This method can realize "one-step mixing" detection of acetamiprid, which makes it a promising analytical tool for monitoring pesticide residue in complicated samples.

Cucurbituril and zwitterionic surfactant-based matrix solid-phase dispersion microextraction to simultaneously determine terpenoids from Radix Curcumae

A rapid, efficient, and environmentally friendly matrix solid-phase dispersion microextraction was established to determine and quantify terpenoids in Radix Curcumae using ultra-high-performance liquid chromatography with a diode array detector. Various parameters affecting the extraction were investigated in detail, such as the grinding time, amount of adsorbent, type and concentration of elution solvent, and pH. The optimization of single-factor and response surface methodology was performed to confirm the best conditions in this procedure. The final optimized conditions were obtained by applying 70 mg of cucurbituril as adsorbent, 149 s as the optimum grinding time, and 228 mM of 3-(N,N-dimethylpalmitylammonio)propanesulfonate aqueous solution (pH 6.5) as the optimal elution solvent. The validated method showed a satisfactory linear range of 0.10-10 µg/mL for curdione and furanodiene, 0.01-10 µg/mL for isocurcumenol and germacrone, and 0.05-10 µg/mL for furanodienone, while the correlation coefficients ranged from 0.9945 to 0.9970. The recoveries of the investigated analytes at two spiked concentration levels (0.1 and 1.0 µg/mL) ranged from 96.53 to 104.60%. In addition, this method displayed acceptable reproducibility (relative standard deviation ≤ 3.66%). The results showed that the newly proposed matrix solid-phase dispersion microextraction method was successfully applied to analyze curdione, isocurcumenol, furanodienone, germacrone and furanodiene in Radix Curcumae samples.

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.

Determination of Methomyl Residue in Tobacco Samples by Heart-Cutting Two-Dimensional Liquid Chromatography with Tandem Mass Spectrometry

A novel heart-cutting two-dimensional liquid chromatography coupled with tandem mass spectrometry (2D-LC-MS/MS) was developed for the qualitative and quantitative analysis of methomyl residue in tobacco. Compared to traditional methodologies, fairly high sensitivity and stability were achieved, and the sample procedure was simplified in the two-dimensional liquid chromatography (2D-LC) method. Although methomyl had poor retention performance in most of the reversed-phase liquid chromatography (RPLC) columns, an effective RP/RP strategy was successfully facilitated. An XB-Phenyl column was employed in the first dimension to effectively remove thousands of interference compounds in the matrix. In the second dimension, an ADME column was applied for further separation. After optimization of the separation conditions, a six-way valve was utilized for direct transformation of the target fraction from the 1st column to the 2nd column. A dynamic range of 2.5 ng/mL to 500 ng/mL was achieved with correlation coefficient (r ²) greater than 0.9995. The limit of detection and limit of quantification were determined to be 0.69 and 2.30 ng/mL, respectively. The 2D-LC method shows high sensitivity, good reproducibility, and recovery for methomyl in tobacco samples. Therefore, the new method was quite suitable for routine analysis.

Health Functions and Related Molecular Mechanisms of Tea Components: An Update Review

Tea is widely consumed all over the world. Generally, tea is divided into six categories: White, green, yellow, oolong, black, and dark teas, based on the fermentation degree. Tea contains abundant phytochemicals, such as polyphenols, pigments, polysaccharides, alkaloids, free amino acids, and saponins. However, the bioavailability of tea phytochemicals is relatively low. Thus, some novel technologies like nanotechnology have been developed to improve the bioavailability of tea bioactive components and consequently enhance the bioactivity. So far, many studies have demonstrated that tea shows various health functions, such as antioxidant, anti-inflammatory, immuno-regulatory, anticancer, cardiovascular-protective, anti-diabetic, anti-obesity, and hepato-protective effects. Moreover, it is also considered that drinking tea is safe to humans, since reports about the severe adverse effects of tea consumption are rare. In order to provide a better understanding of tea and its health potential, this review summarizes and discusses recent literature on the bioactive components, bioavailability, health functions, and safety issues of tea, with special attention paid to the related molecular mechanisms of tea health functions.

Balls-in-tube matrix solid phase dispersion (BiT-MSPD): An innovative and simplified technique for multiresidue determination of pesticides in fruit samples

Sample preparation of complex matrices, like food samples, continues to be a challenge demanding great effort for improvements. In this study, a new technique named balls-in-tube matrix solid-phase dispersion (BiT-MSPD) is proposed based on a simplification of the conventional MSPD technique being all sample preparation performed directly in a closed extraction tube with the assistance of steel balls. An innovative method using BiT-MSPD was successfully established for the determination of 133 pesticide residues in apple, peach, pear and plum by ultra-high performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS). Several sorbents were evaluated as solid support in different proportions with the sample. The homogenization step using mortar, glass rod or steel balls, with methanol and acetonitrile as extraction solvent, was evaluated. Vortex and ultrasound assisted extractions were also tested. Best results were obtained with C18, homogenization with steel balls, acetonitrile as solvent and ultrasound assisted extraction. Validation presented adequate trueness and precision results for the evaluated pesticides with recovery results ranging from 72 to 113% and RSD ≤ 17%. Practical limit of detection (LOD) and quantification (LOQ) for the compounds were 3 and 10 µg kg^-1, respectively. The developed method proved to be easier and faster to perform than the MSPD, considering that extraction and clean-up are performed in the same tube without the need to transfer to cartridges, recipients or to use a separate clean-up step. The proposed BiT-MSPD technique was successfully applied to fruit samples and has great potential to be applied in other matrices, like cereals and meat, since the steel balls promote an efficient sample dispersion and extraction of pesticides. The BiT-MSPD permit a fully automation of the entire sample preparation step.

Detection of systemic pesticide residues in tea products at trace level based on SERS and verified by GC-MS

Surface-enhanced Raman spectroscopy (SERS) has the potential to detect pesticide residues in agricultural products. However, some systemic pesticides, such as chlorpyrifos, can enter the plant tissue, and not just stay on the surface. Consequently, many SERS studies halted at practical application because of its complexity. In this work, SERS technology was used to detect chlorpyrifos residues in tea products at the semiquantitative level. A simple pretreatment method effectively avoided interference of other fluorescent substances, and all major peaks could be distinguished on the basis of a novel substrate. A principal component analysis algorithm was applied to form a regression model, and a nanogram detection limit was obtained. Furthermore, chlorpyrifos residues in the same tea products were also measured by gas chromatography-mass spectrometry, and the results show a small range of errors. From the comparative study of the two detection methods, the results suggest the great promise of SERS technology for rapid inspection of agricultural products.

Stereoselective Analysis of Chiral Pyrethroid Insecticides Tetramethrin and α-Cypermethrin in Fruits, Vegetables, and Cereals

This manuscript presents an effective and robust method for simultaneous stereoselective determination of two pyrethroid insecticides, tetramethrin and α-cypermethrin in different food products by high-performance liquid chromatography. Enantioseparation was carried out using reversed-phase chromatography, and the influences of four polysaccharide-based chiral columns, mobile phase composition, and column temperature on retention were fully investigated. Satisfactory separation was obtained on Chiralpak IG column using acetonitrile-water (75:25, v/v) under isocratic conditions. To extract and purify the target analytes from food matrices, matrix solid-phase dispersion was employed with C₁₈ as dispersant and primary secondary amine as well as graphitized carbon black as cleanup sorbents. Response surface method based on Box-Behnken design was implemented to assist optimization of the extraction variables. Then, method validation was done in real samples including specificity, linearity, sensitivity, trueness, precision, as well as stability, and its analytical performance fulfills the criteria recommended by the European Union SANTE/11945/2015, demonstrating its applicability in studying the stereochemistry of chiral tetramethrin and α-cypermethrin in food products.

The determination of pesticides in tea samples followed by magnetic multiwalled carbon nanotube-based magnetic solid-phase extraction and ultra-high performance liquid chromatography-tandem mass spectrometry

A simple and efficient method regarding ultrasound-assisted extraction combined with magnetic solid-phase extraction (UA-MSPE) by UHPLC-MS/MS was set up for the determination of three pesticides in tea leaf samples.

Carboxylated Multiwalled Carbon Nanotubes as Dispersive Solid-Phase Extraction Sorbent to Determine Eighteen Polychlorinated Biphenyls in Vegetable Samples by Gas Chromatography-Mass Spectrometry

A simple, rapid, and reliable method based on dispersive solid-phase extraction (d-SPE) and gas chromatography-mass spectrometry (GC-MS) was developed for quantitating polychlorinated biphenyls (PCBs) in vegetable samples. Parameters affecting both the extraction yields and cleanup efficiency, including the type and volume of extraction solvent, extraction time, type and volume of cleanup sorbent, and cleanup time, were optimized. Matrix effects were evaluated, and matrix-matched calibration was recommended. Under the optimized conditions, carboxylated multiwalled carbon nanotubes (MWCNTs-COOH), which exhibit excellent adsorption capabilities due to large surface area and unique structure, were employed as d-SPE sorbent to remove interfering substances, rather than the analytes, from vegetable samples. Satisfactory linear relationship was observed for all PCBs across a concentration range of 5-500 μg/kg with correlation coefficients no less than 0.9993. Four representative vegetables (cucumber, tomato, lettuce, and cabbage) were selected as matrices for method validation. Each matrix was spiked at concentrations of 5, 10, and 100 μg/kg to evaluate recoveries, which ranged from 84.5% to 116.5% with relative standard deviations (n=6) between 0.6% and 17.6%. The limits of detection and the limits of quantification ranged from 0.3 to 1.4 μg/kg and 0.8 to 4.5 μg/kg, respectively. Twelve real vegetable samples were analyzed using the proposed method. Three of the target PCBs were detected in one lettuce sample with the total concentration of 17.9 μg/kg.

The synthesis of Zr-metal-organic framework functionalized magnetic graphene nanocomposites as an adsorbent for fast determination of multi-pesticide residues in tobacco samples

In this paper, a simple and reliable method has been established to determine the residues of nine pesticides in tobacco by using GC-MS coupled with magnetic solid phase extraction. A novel magnetic Zr-MOF nanocomposite based on graphene was synthesized, and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy and N2 adsorption-desorption measurements. The prepared material has the advantage of large surface area (178 m2/g), good magnetic response and high thermal stability, which is shown to be suited for the fast enrichment of multi-pesticides in tobacco matrix. The extraction conditions including amount of adsorbent, adsorption time, eluting solvent as well as desorption time were investigated. The whole process of pretreatment is accomplished within 10 min. This method shows low limit of detection, wide linear range and good reproducibility (relative standard deviations <12.7%), satisfactory recoveries were obtained, ranging from 57.9% to 126.3% for tobacco samples.

Sensitive Screening Method for Determination of Pyrethroids in Chicken Eggs and Various Meat Samples by Gas Chromatography and Electron Capture Detection

A sensitive and reproducible screening analytical method is described for the determination of six pyrethroids (phenothrin, permethrin, cyfluthrin, cypermethrin, deltamethrin, fenvalerate) in egg and meat samples by gas chromatography and electron capture detection (GC-ECD). A fast cleanup procedure, based on solid-phase extraction has been used, ensuring reduced solvent consumption and time and allowing the simultaneous preparation of multiple sample extracts. Under the optimal chromatographic conditions, an efficient separation was obtained with a total analysis time of less than 60 min, including the extraction-purification steps. Good responses for the six pyrethroids were obtained in a range of 50-500 μg L^-1, with linear coefficients higher than 0.9992. Instrumental limits of detection were between 0.22 and 0.63 μg L^-1, corresponding to 0.04 and 0.13 μg kg^-1 in the matrix. Detection limits in chicken eggs and various meat samples, calculated on spiked samples, were in the range 0.05-0.25 μg kg^-1 and 0.07-0.23 μg kg^-1, respectively. The validation results confirmed that the proposed GC-ECD method can be used as a reliable screening tool for the determination of pyrethroids in official check analyses. The method was extensively validated following the European directives, demonstrating its conformity in terms of selectivity, sensitivity, recovery, precision, and measurement uncertainty.

Migration and Accumulation of Octachlorodipropyl Ether in Soil-Tea Systems in Young and Old Tea Gardens

The migration and accumulation of octachlorodipropyl ether (OCDPE) in soil-tea systems were investigated using a gas chromatography-electron capture detector (GC-ECD) method in young and old tea gardens. When the residual concentration of OCDPE was 100 g a.i. hm^-2 in soils, the peak concentrations of OCDPE in fresh leaves of young and old tea plants were 0.365 mg/kg and 0.144 mg/kg, taking 45 days and 55 days, respectively. Equations for the accumulation curves of OCDPE in fresh leaves of young and old tea plants were C_t = 0.0227e^0.0566t (R² = 0.9154) and C_t = 0.0298e^-0.0306t (R² = 0.7156), and were C_t = 3.8435e^0.055t (R² = 0.9698) and C_t = 1.5627e^-0.048t (R² = 0.9634) for dissipation curves, with a half-life of 14.4 days and 12.6 days, respectively. These results have practical guiding significance for controlling tea food safety.

Degradation Processes of Pesticides Used in Potato Cultivations

Potato is one of the most important crops, after maize, rice and wheat. Its global production is about 300 million tons per year and is constantly increasing. It grows in temperate climate and is used as a source of starch, food, and in breeding industry.Potato cultivation requires application of numerous agro-technical products, including pesticides, since it can be affected by insects, weeds, fungi, and viruses. In the European Union the most frequently used pesticides in potato cultivations check are: thiamethoxam, lambda-cyhalothrin and deltamethrin (insecticides), rimsulfuron (herbicide) and metalaxyl (fungicide).Application of pesticides improves crop efficiency, however, as pesticides are not totally selective, it affects also non-target organisms. Moreover, the agrochemicals may accumulate in crops and, as a consequence, negatively influence the quality of food products and consumer health. Additional risks of plant protection products are related to their derivatives, that are created both in the environment (soil, water) and in plant organisms, since many of these compounds may exhibit toxic effects.This article is devoted to the degradation processes of pesticides used in potato crop protection. Attention is also paid to the toxicity of both parent compounds and their degradation products for living organisms, including humans. Information about the level of pesticide contamination in the environment (water, soil) and accumulation level in edible plants complement the current knowledge about the risks associated with widespread use of thiamethoxam, lambda-cyhalothrin and deltamethrin, rimsulfuron and metalaxyl in potato cultivation.

Utilizing a novel sorbent in the solid phase extraction for simultaneous determination of 15 pesticide residues in green tea by GC/MS

Pesticide residues exceeding standard in green tea is a widespread problem of the world's attention, containing organochlorine pesticides (OCPs), organophosphorus pesticides (OPPs), and pyrethroids. In this research, three dimensionally honeycomb Mg-Al layered double oxide (TDH-Mg-Al-LDO) combined with graphitized carbon black (GCB), packed as a column, was used as a novel solid phase extraction sorbent, applying in simultaneous determination of 15 pesticide residues in green tea coupled with GC-MS. Compared with different type of SPE column, it showed that TDH-Mg-Al-LDO exhibited great advantages in the extraction of 15 pesticide residues from green tea, which was seldom reported before. Different experiment conditions, such as combination order of Mg-Al-LDO and GCB, dosage of sorbents, type and volume of eluting solvent were thoroughly studied and optimized. The limits of detection (LODs) of 15 pesticides ranged from 0.9 to 24.2ng/g and the limits of quantifications (LOQs) were ranging from 3.0 to 80.0ng/g. The recoveries using this method at three spiked concentration levels (10, 100 and 500ng/g for Fenthion, P,P'-DDE, O,P'-DDT, P,P'-DDD and Bifenthrin, 100, 500 and 2000ng/g for the others) range from 71.1 to 119.0%. The relative standard deviation (RSD) was from 0.1 to 7.6% in all case. The result indicated that the proposed analytical method had been successfully applied for the simultaneous determination of 15 pesticide residues in commercial green tea.