A ratiometric fluorescence and colorimetry dual-signal sensing strategy based on o-phenylenediamine and AuNCs for determination of Cu2+ and glyphosate.

A ratiometric fluorescence sensing strategy has been developed for the determination of Cu2+ and glyphosate with high sensitivity and specificity based on OPD (o-phenylenediamine) and glutathione-stabilized gold nanoclusters (GSH-AuNCs). Water-soluble 1.75-nm size GSH-AuNCs with strong red fluorescence and maximum emission wavelength at 682 nm were synthesized using GSH as the template. OPD was oxidized by Cu2+, which produced the bright yellow fluorescence oxidation product 2,3-diaminophenazine (DAP) with a maximum fluorescence emission peak at 570 nm. When glyphosate existed in the system, the chelation between glyphosate and Cu2+ hindered the formation of DAP and reduced the fluorescence intensity of the system at the wavelength of 570 nm. Meanwhile, the fluorescence intensity at the wavelength of 682 nm remained basically stable. It exhibited a good linear relationship towards Cu2+ and glyphosate in water in the range 1.0-10 µM and 0.050-3.0 µg/mL with a detection limit of 0.547 µM and 0.0028 µg/mL, respectively. The method was also used for the semi-quantitative determination of Cu2+ and glyphosate in water by fluorescence color changes visually detected by the naked eyes in the range 1.0-10 µM and 0.30-3.0 µg/mL, respectively. The sensing strategy showed higher sensitivity, more obvious color changes, and better disturbance performance, satisfying with the detection demands of Cu2+ and glyphosate in environmental water samples. The study provides a reliable detection strategy in the environment safety fields.

Method Validation for Multi-Pesticide Residue Determination in Chrysanthemum.

The chrysanthemum can be consumed in various forms, representing the "integration of medicine and food". Quantitative analysis of multi-pesticide residues in chrysanthemum matrices is therefore crucial for both product-safety assurance and consumer-risk evaluation. In the present study, a simple and effective method was developed for simultaneously detecting 15 pesticides frequently used in chrysanthemum cultivation in three matrices, including fresh flowers, dry chrysanthemum tea, and infusions. The calibration curves for the pesticides were linear in the 0.01-1 mg kg-1 range, with correlation coefficients greater than 0.99. The limits of quantification (LOQs) for fresh flowers, dry chrysanthemum tea, and infusions were 0.01-0.05 mg kg-1, 0.05 mg kg-1, and 0.001-0.005 mg L-1, respectively. In all selected matrices, satisfactory accuracy and precision were achieved, with recoveries ranging from 75.7 to 118.2% and relative standard deviations (RSDs) less than 20%. The validated method was then used to routinely monitor pesticide residues in 50 commercial chrysanthemum-tea samples. As a result, 56% of samples were detected with 5-13 pesticides. This research presents a method for the efficient analysis of multi-pesticide residues in chrysanthemum matrices.

SPE-UPLC-MS/MS for Determination of 36 Monomers of Alkylphenol Ethoxylates in Tea.

Alkylphenol ethoxylates (APEOs) represent a non-ionic surfactant widely used as adjuvants in pesticide formulation, which is considered to cause an endocrine-disrupting effect. In the current study, we established a detection method for the APEOs residue in tea based on solid-phase extraction (SPE) for the simultaneous analysis of nonylphenol ethoxylates (NPEOs) and octylphenol ethoxylates (OPEOs) by UPLC-MS/MS. In the spiked concentrations from 0.024 to 125.38 µg/kg for 36 monomers of APEOs (nEO = 3-20), the recoveries of APEOs range from 70.3-110.7% with RSD ≤ 16.9%, except for OPEO20 (61.8%) and NPEO20 (62.9%). The LOQs of OPEOs and NPEOs are 0.024-6.27 and 0.16-5.01 µg/kg, respectively. OPEOs and NPEOs are detected in 50 marketed tea samples with a total concentration of 0.057-12.94 and 0.30-215.89 µg/kg, respectively. The detection rate and the range of the monomers of NPEOs are generally higher than those of OPEOs. The current study provides a theoretical basis for the rational use of APEOs as adjuvants in commercial pesticide production.

Method validation for detection of afidopyropen and M440I007 in tea.

BACKGROUND: Afidopyropen is a novel biorational insecticide for controlling piercing pests with great potential for application in tea gardens that can form the metabolite M440I007 when utilized for crops. However, because of a lack of analytical method for afidopyropen and M440I007 in tea, there is no means of monitoring the residues. Therefore, method development, validation and simultaneous determination of afidopyropen and M440I007 in fresh tea leaves, dried tea and tea infusion is of prime significance. RESULTS: A TPT cartridge-based method was developed for the solid phase extraction of afidopyropen and M440I007 from tea matrices. Extraction and clean-up conditions, including the composition, volume and temperature of elutions, were optimized to achieve the best results. Both targets were extracted using water and acetonitrile, with a water:acetonitrile (v/v) ratio of 4:10 for fresh leaves and 8:10 for dried tea, which were then cleaned and analyzed using ultraperformance liquid chromatography-tandem mass spectrometry. Both analytes demonstrated excellent linearity with a correlation coefficient above 0.998. The optimized analytical method offered limits of quantifications of 0.005, 0.005 and 0.002 mg kg-1 (converted to dried tea) in fresh tea shoots, dried tea and tea infusion for both targets, respectively. Average recoveries of afidopyropen and M440I007 ranged from 79.0% to 101.5%, with relative standard deviations ≤ 14.7%. CONCLUSION: The results showed that the method of determination for these insecticides in tea matrices was practical and efficient. © 2023 Society of Chemical Industry.

Residue degradation, transfer and risk assessment of pyriproxyfen and its metabolites from tea garden to cup by ultra performance liquid chromatography tandem mass spectrometry.

BACKGROUND: Tea is one of the most popular drinks in the world. The growth of tea plant is inseparable from the control of pesticides on diseases and pests. Pyriproxyfen is used as a pesticide substitute to control insect pests in tea gardens, but little is known about its residue degradation. Here, we performed an integrative study of the degradation and metabolism of pyriproxyfen from the tea garden to the cup. RESULTS: The dissipation half-life of pyriproxyfen during tea growth was 2.74 days, and five metabolites PYPAC, PYPA, DPH-Pyr, 5''-OH-Pyr, and 4'-OH-Pyr were generated. The total processing factors for pyriproxyfen in green tea and black tea were 2.41-2.83 and 2.77-3.70, respectively. The residues of pyriproxyfen and its metabolites were affected by different processing steps. The total leaching rates of pyriproxyfen from green tea and black tea into their infusions were 9.8-12.3% and 5.3-13.8%, respectively. The leaching rates of the five metabolites were higher than that of pyriproxyfen and increased the intake risk. CONCLUSION: To ensure safe consumption, the recommended maximum residue limit value of pyriproxyfen in tea can be set to 5 mg kg-1 and the pre-harvest interval can be set to 5 days. © 2022 Society of Chemical Industry.

Residue analysis and dietary exposure risk assessment of acibenzolar-S-methyl and its metabolite acibenzolar acid in potato, garlic, cabbage, grape and tomato.

Acibenzolar-S-methyl (ASM) is one of the most effective plant resistance activators and protects against a broad spectrum of fungal, bacterial and viral pathogens. A rapid, efficient and high-throughput analysis method for ASM and its metabolite acibenzolar acid in fruits and vegetables was developed using potato, garlic, cabbage, grape and tomato as representative commodities by modified QuEChERS and UPLC-MS/MS. The modified procedure showed satisfying recoveries (70-108%) fortified in the range of 0.01-1 mg/kg with relative standard deviations (RSDs) lower than 17.7%. With the established analytical method, the dietary risk of ASM in fruits and vegetables from Chinese markets were further monitored using risk quotient (RQ) method. The RQ value based on ASM residue in China are far less than 1, elucidating that the potential health risk induced by ASM ingestion for Chinese population is not significant. Comparing the residue and risk assessment results of ASM in agricultural products in China to those in Codex, the maximum residue limits (MRLs) for ASM on garlic, cabbage and tomato established by CAC (Codex Alimentarius Commission) can be safely adopted in China, whereas the MRLs on potato and grape in China should be proposed as 0.01 mg/kg.

Residue behavior and safety evaluation of pymetrozine in tea.

BACKGROUND: Pymetrozine is a widely used pesticide. It is challenging to analyze and difficult to manage due to the large gap in its global maximum residue limits (MRLs) in tea. The development of a high-efficiency detection method for the evaluation of the transfer of residual pymetrozine from tea plantations to tea cups is therefore of prime significance. RESULTS: An analytical method for the determination of pymetrozine residues in tea was established based on Cleanert PCX solid-phase extraction. The average recoveries were 72.2-93.7%, with relative standard deviations (RSDs) of less than 12%. The limits of quantification (LOQs) were 0.005 mg·kg-1 in fresh tea leaves and dry tea, and 0.00025 mg·L-1 in tea brew. Pymetrozine degraded rapidly in tea plants with a half-life (t1/2 ) of 1.9 days in open tea plantations, and decreased by 9.4-23.7% in the green tea-processing procedure, which was concentration dependent. The residual pymetrozine levels in green tea collected at 6 and 21 days were below the MRLs in China and EU at a dosage of 30 g a.i. ha-1 , respectively. The leaching rates of pymetrozine from dry tea to tea brew were 58.7-96.3%. Hazard quotient (HQ) values of pymetrozine were significantly <100% when tea shoots were plucked in 6 days, which indicated a negligible risk to humans. CONCLUSION: This work allows the determination of residual pymetrozine in tea and illustrates a low intake risk with the use of pymetrozine in tea plantations. It could serve as reference for further regulation consideration for maximum residue limits (MRLs). © 2020 Society of Chemical Industry.

Residue dissipation, transfer and safety evaluation of picoxystrobin during tea growing and brewing.

BACKGROUND: Picoxystrobin is a new osmotic and systemic broad-spectrum methoxyacrylate fungicide with a good control effect on tea anthracnose, so it has been proposed to spray picoxystrobin before the occurrence and onset of tea anthracnose during tea bud growth in order to protect them. However, there are few reports about the residue analysis method, field dissipation, terminal residue and risk assessment of picoxystrobin in tea. And there is no scientific and reasonable maximum residue limit of picoxystrobin in green tea. RESULTS: A rapid and sensitive analysis method for picoxystrobin residue in fresh tea leaf, green tea, tea infusion and soil was established by UPLC-MS/MS. The spiked recoveries of picoxystrobin ranged from 73.1% to 111.0%, with relative standard deviations from 1.8% to 9.2%. The limits of quantitation were 20 µg kg-1 in green tea, 8 µg kg-1 in fresh tea leaves and soil and 0.16 µg kg-1 in tea infusion. The dissipation half-lives of picoxystrobin in fresh tea leaf and soil were 2.7-6.8 and 2.5-14.4 days, respectively. And the maximum residue of picoxystrobin in green tea was 15.28 mg kg-1 with PHI at 10 days for terminal test. The total leaching rate of picoxystrobin during green tea brewing was lower than 35.8%. CONCLUSIONS: According to safety evaluation, the RQc and RQa values of picoxystrobin in tea after 5 to 14 days for the last application were significantly lower than 1. Therefore, the maximum residue limit value of picoxystrobin in tea that we suggest to set at 20 mg kg-1 can ensure the safety of tea for human drinking. © 2020 Society of Chemical Industry.

Enantioselective residue analysis of oxathiapiprolin and its metabolite in tea and other crops by ultra-high performance liquid chromatography-tandem mass spectrometry.

Oxathiapiprolin is the first chiral piperidinyl thiazole isoxazoline fungicide developed to control downy mildew and other diseases, and there were no prior reports on its enantiomeric residue. In this study, a modified quick, easy, cheap, effective, rugged, and safe extraction and purification method followed by ultra-high performance liquid chromatography-tandem mass spectrometry determination was first developed and validated for the residue analysis of oxathiapiprolin enantiomers and its metabolite IN-E8S72 in green tea and other crops. Oxathiapiprolin enantiomers and IN-E8S72 were separated on a chiral Lux Cellulose-3 column with the use of 0.1% formic acid in acetonitrile and 5 mmol/L ammonium acetate in water as mobile phases. IN-E8S72 was eluted first, followed by (-)-oxathiapiprolin, and then (+)-oxathiapiprolin. The recoveries ranged from 53.3 to 125.3% with relative standard deviations ranging from 1.4 to 16.0%. The limits of quantification for (-)-oxathiapiprolin and (+)-oxathiapiprolin were 0.005 mg/kg in romaine lettuce, head cabbage, potato, grape, and garlic, 0.01 mg/kg in soybean and pea, and 0.025 mg/kg in green tea and dry pepper. The limits of quantification of IN-E8S72 were twice those of (-)-oxathiapiprolin. Screening results with real market samples indicated that there was no enantiomeric excess in the oxathiapiprolin residue in romaine lettuce.

Residue dissipation and dietary exposure risk assessment of methoxyfenozide in cauliflower and tea via modified QuEChERS using UPLC/MS/MS.

BACKGROUND: Methoxyfenozide possesses efficacy against a variety of lepidopteron pests, including the major pests in cauliflower and tea, so it is of great importance to generalize the practical use of methoxyfenozide in the field. RESULTS: An efficient method was developed and validated in both vegetable matrix and extract-rich matrix (cauliflower and tea) using modified QuEChERS combined with UPLC/MS/MS analysis. The recoveries in cauliflower, made tea and tea shoots ranged from 94.5 to 108.0%, from 85.0 to 91.6% and from 77.3 to 82.0% respectively, with relative standard deviations (RSDs) below 17.3% in all cases. The field results showed that methoxyfenozide dissipated in cauliflower with half-life (t1/2 ) at 2.5-3.5 days and in tea with t1/2 at 1.2 days. Combining the above experimental data and statistical food intake values, the risk quotient (RQ) values were significantly lower than 1. CONCLUSION: The quantification method of methoxyfenozide in cauliflower or tea has not been established until this study. The dissipation and dietary exposure risk assessment of methoxyfenozide in cauliflower and tea were investigated in the field. Methoxyfenozide dissipated rapidly in cauliflower despite different climates, and it dissipated faster in tea. The dietary risk of methoxyfenozide through cauliflower or tea was negligible to humans. This study not only provides guidance for the safe use of methoxyfenozide but also serves as a reference for the establishment of maximum residue limits (MRLs) in China. © 2019 Society of Chemical Industry.

Application and enantioselective residue determination of chiral pesticide penconazole in grape, tea, aquatic vegetables and soil by ultra performance liquid chromatography-tandem mass spectrometry.

Penconazole is a typical triazole fungicide with wide use on fruits, vegetables, and tea plants to control powdery mildew. In the present study, an efficient graphite carbon black solid phase extraction (GCB-SPE) purification combined with chiral ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was developed for determination of penconazole enantiomers in different complex matrices, including grape, tea, soil, lotus root, lotus leaf, lotus seed and hulls. The method was then applied to investigate the enantioselective dissipation of penconazole enantiomers in a real field experiment of grape and soil. As a result, a satisfactory separation of penconazole enantiomers on a chiral Lux Cellulose-2 column (150 mm × 2 mm i.d., 3 µm) was obtained with 0.1% formic acid in methanol and 10 mmol L-1 ammonium acetate in water (75/25, v/v) as mobile phase at 0.25 mL min-1. The enantiomer (+)-penconazole was firstly eluted, and (-)-penconazole was then eluted. The method showed reliable performances in linearity, recovery and precision, the recoveries of (+)-penconazole and (-)-penconazole in all of six matrices were between 70.5% and 121.0% with the relative standard deviations (RSDs) ranging from 0.8% to 23.6% at the low, medium and high spiked levels. The limits of quantitation (LOQs) of this method were lower than 0.0025 mg kg-1 in grape, soil and lotus root, 0.005 mg kg-1 in lotus leaf, lotus seed meat and lotus seed shell, and 0.0125 mg kg-1 in tea. Results of field trials indicated that (-)-penconazole degraded faster than its (+)-isomer in grape. While only a moderate stereoselectivity was observed in soil, with (-)-penconazole preferential degraded. The proposed method could be used to investigate enantioselective environmental behavior of penconazole enantiomers in complex matrices. And results in this study could provide useful information on realistic risk assessment of penconazole in grape.

Residue Degradation and Risk Assessment of Difenoconazole and Its Metabolite during Tea Growing, Processing and Brewing by Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry Determination.

Residue dissipation and risk assessment of difenoconazole and its metabolite difenoconazole-alcohol during tea growing, processing, and brewing was first investigated by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The limits of quantification for both difenoconazole and difenoconazole-alcohol were 0.001 mg/kg in fresh tea leaves and tea, and 0.0002 mg/L in tea infusion. In field trials, the dissipation half-lives of difenoconazole in fresh tea leaves was 1.77 days. After spraying, the residues of difenoconazole-alcohol increased and then gradually dissipated like difenoconazole. After 14 days, the dissipation rates of difenoconazole and difenoconazole-alcohol reached 99%. When fresh tea leaves were harvested on different days, the total processing factors (PFs) of difenoconazole and difenoconazole-alcohol for green tea were 0.86-1.05 and 0.78-0.85, respectively, while the total PFs for black tea were 0.83-1.13 and 0.82-1.66, respectively. Metabolism of difenoconazole was accelerated during tea processing. When brewing black tea, the leaching rates (LRs) of difenoconazole and difenoconazole-alcohol were 8.4-17.9% and 31.8-38.9%, respectively, while when brewing green tea, the LRs were 15.4-23.5% and 30.4-50.6%, respectively. The LRs of difenoconazole and difenoconazole-alcohol in black tea were higher than those in green tea. The potential threat to human health for dietary intake of difenoconazole and difenoconazole-alcohol residues from tea consumption is negligible. However, the dietary risk of difenoconazole in fruits and vegetables that are essential for daily diets is concerning, with a risk probability of 158%.

High-throughput analytical techniques for multiresidue, multiclass determination of 653 pesticides and chemical pollutants in tea--Part III: Evaluation of the cleanup efficiency of an SPE cartridge newly developed for multiresidues in tea.

A comparative study was conducted over three stages on the cleanup efficiency of SPE cartridge Cleanert TPT, newly developed for multigroups of pesticide residues in tea. In Stage I, different SPE cartridges C18, graphite carbon black (GCB), primary secondary amine (PSA), and amino (NH2) were purchased and combined into 12 different sequences. Through the comparative test on cleanup efficiency of 84 representative pesticides in tea, Envi-Carb GCB + PSA with a good cleanup effect was selected. In Stage II, GC/MS test results from the comparative study of the extraction efficiency of 201 pesticides spiked into green tea and Woolong tea with Cleanert TPT and Envi-Carb + PSA SPE showed that average recoveries fell within 70-110% and RSD <20% for 193 and 184 pesticides, respectively, for green tea, accounting for 96.0 and 91.0% of the total number, respectively. GC/MS/MS test results also found 193 and 184 pesticides, respectively, meeting the recovery and RSD conditions, accounting for 96.0 and 91.5%, respectively, of the total number. For Woolong tea samples, GC/MS results showed that with Cleanert TPT and Envi-Carb + PSA SPE for cleanup, there were 192 and 177 pesticides, respectively, meeting the conditions, accounting for 95.5 and 88.1% of the total number, respectively. GC/MS/MS results demonstrated that there were 195 and 184 pesticides, respectively, meeting the conditions, accounting for 97.0 and 91.5% of the total number, respectively. It was seen that Cleanert TPT was superior to Envi-Carb + PSA in cleanup efficiency, whether for green or Woolong tea samples, or GC/MS or GC/MS/MS determination. In Stage III, 61104 results of the average content value of pesticides and RSD (two teas xtwo Youden pair concentrations x two kinds of SPE cartridges x two instruments x 19 tests x 201 pesticides) were derived from the 19 times stability tests over 3 months by paralleling three samples every 5 days via two instruments with two kinds of SPE cartridges for cleanup, respectively, against Youden Pair samples of the 201 incurred pesticides from green and Woolong teas. The statistical analysis found that detected values from the target pesticides of the incurred Youden pair samples showed no marked differences with cleanup by either Cleanert TPT or Envi-Carb + PSA, whether for green or Woolong tea, or G/IMS or G/IM/IMS. The test results using the two aforementioned kinds of SPE cleanup for above 93% pesticides had a tolerance less than 15%, which testifies that both cartridge cleanups met the requirement for pesticide residue analysis.

A Turn-On Fluorescence Sensor Based on Nitrogen-Doped Carbon Dots and Cu2+ for Sensitively and Selectively Sensing Glyphosate.

Glyphosate has excellent herbicidal activity, and its extensive use may induce residue in the environment and enter into humans living through the food chain, causing negative impact. Here, water-soluble 1.55 nm size nitrogen-doped carbon quantum dots (NCDs) with strong blue fluorescence were synthesized using sodium citrate and adenine. The maximum excitation and emission wavelengths of NCDs were 380 nm and 440 nm, respectively. The above synthesized NCDs were first used for the construction of a fluorescence sensor for glyphosate detection. It was found that Cu2+ could quench the fluorescence of NCDs effectively through the photoinduced electron transfer (PET) process, which was confirmed using fluorescence lifetime measurements. Additionally, the fluorescence was restored with the addition of glyphosate. Hence, a sensitive turn-on fluorescence sensor based on NCDs/Cu2+ for glyphosate analysis was developed. The LODs of glyphosate for water and rice samples were recorded as 0.021 µg/mL and 0.049 µg/mL, respectively. The sensor was applied successfully for ultrasensitive and selective detection of glyphosate in environmental water and rice samples with satisfied recoveries from 82.1% to 113.0% using a simple sample pretreatment technique. The proposed strategy can provide a significant potential for monitoring glyphosate residue in water and agricultural product samples.

Residue behavior and risk assessment of afidopyropen and its metabolite M440I007 in tea.

Afidopyropen, a novel insecticide, is highly effective against piercing insects such as the tea leafhopper. The residual levels of afidopyropen and M440I007 in tea cultivation, processing, and brewing were studied. During tea cultivation, afidopyropen dissipated faster in fresh tea shoots in the rainy season (T1/2 of 1.2-2.5 d) than that in the dry season (T1/2 of 3.1-4.4 d); afidopyropen was metabolized into M440I007, the level of which peaked in 1 d, and degraded rapidly (over 90 %) afterward 3 d. The green tea processing steps had little effect on decreasing the afidopyropen residue (PF of 0.90-1.18). Low infusion rates of afidopyropen (16.7 %-17.7 %) and M440I007 (4.1 %-6.2 %) were observed from dry green tea to infusion; furthermore, the risk of ingesting afidopyropen from drinking tea was low, with the risk quotient values < 0.0001. This study can offer guidance on the rational application of afidopyropen in tea plants.

The metabolism and dissipation behavior of tolfenpyrad in tea: A comprehensive risk assessment from field to cup.

The metabolites of pesticides usually require rational risk assessment. In the present study, the metabolites of tolfenpyrad (TFP) in tea plants were identified using UPLC-QToF/MS analysis, and the transfer of TFP and its metabolites from tea bushes to consumption was studied for a comprehensive risk assessment. Four metabolites, PT-CA, PT-OH, OH-T-CA, and CA-T-CA, were identified, and PT-CA and PT-OH were detected along with dissipation of the parent TFP under field conditions. During processing, 3.11-50.00 % of TFP was further eliminated. Both PT-CA and PT-OH presented a downward trend (7.97-57.89 %) during green tea processing but an upward trend (34.48-124.17 %) during black tea manufacturing. The leaching rate (LR) of PT-CA (63.04-101.03 %) from dry tea to infusion was much higher than that of TFP (3.06-6.14 %). As PT-OH was no longer detected in tea infusions after 1 d of TFP application, TFP and PT-CA were taken into account in the comprehensive risk assessment. The risk quotient (RQ) assessment indicated a negligible health risk, but PT-CA posed a greater potential risk than TFP to tea consumers. Therefore, this study provides guidance for rational TFP application and suggests the sum of TFP and PT-CA residues as the maximum residual limit (MRL) in tea.

Uptake, translocation, and metabolism of anthracene in tea plants.

The origin of 9, 10-anthraquinone (AQ) contamination in tea remains unclear at present. The objective of this study was to test the hypothesis that AQ could be produced from the precursor anthracene in tea plantations. To test this hypothesis, the uptake, translocation, and transformation of anthracene in tea (Camellia sinensis) seedlings using hydroponic experimentation was investigated. Anthracene concentrations in tea tissues rose with increased anthracene exposure, which in the roots were significantly (p < 0.05) higher than those in aboveground parts at the end of the exposure. These results indicated that anthracene tended to be adsorbed into tea seedling via the roots and accumulated largely within roots. The three main pathways of anthracene degradation in tea seedlings were suggested: oxygen was incorporated in the 9th and 10th positions of anthracene resulting in AQ (I) and anthrone (II), and naphthalene was formed by ring fission of anthracene via methylanthracene (III). The principal anthracene metabolites were AQ and anthrone. The concentrations of AQ, like anthrone, were markedly elevated in the roots than those in stems throughout the entire exposure period. Moreover, the translocation factors for anthracene and its primary metabolites AQ and anthrone from roots to stems were persistently lower than 0.1, demonstrating a poor translocation from roots to the aboveground regions. However, tea seedlings could take anthracene up from water and translocate it to the leaves. It was a possible risk for AQ contamination in tea leaves continuously exposed to anthracene for long periods of time because tea plants were perennial crops.

Visual detection of perchlorate in aqueous solution using alkali methylene blue.

Perchlorate (ClO4-) has aroused wide concern as a global ecosystem pollutant, especially in the aquatic environment. A rapid and visible detection of ClO4- in aqueous solution using alkali methylene blue (MB) and liquid-liquid extraction (LLE) was established with high selectivity and sensitivity. The alkali MB exclusively change from red into blue in an organic solvent when exposed to aqueous ClO4-. The organic solvent, amount of MB and the alkalinity of the solution were systematically optimized, while the underlying mechanism was revealed using UV-Vis spectroscopy and mass spectrometry. Under the optimum conditions, the UV-Vis absorbance at 600 nm showed a good linear relationship with the concentrations of ClO4- in the range of 0.0025-0.025 mM (R2 = 0.9945). The visual detection limit was 0.005 mM in environmental water and 0.02 mM in black tea infusion. This method provides an economical and simple visual detection of ClO4- in an aqueous solution.

Dissipation behavior and risk assessment of tolfenpyrad from tea bushes to consuming.

The dissipation behavior of tolfenpyrad, a widely used pyrazole insecticide in tea plantations, was investigated during tea bushes growing, manufacturing and brewing. Tolfenpyrad dissipated fast on the tea bushes with the half-lives of 1.8-2.3 days. Manufacturing processes of green tea and black tea further reduced the tolfenpyrad residue by 3.5%-36.4%. The average processing factors (PFs) of tolfenpyrad ranged from 0.68 to 1.40 and 0.84 to 1.30 during the processing of green tea and black tea, respectively. Then a low infusion factor of 9.8%-19.9% was observed during the brewing of made tea, as the water solubility of tolfenpyrad was only 0.087 mg/L. Therefore, more than 96% of the initial deposition of tolfenpyrad was dissipated and not accessible for consuming. Results of the risk quotient (RQ) assessment also indicated a negligible health risk by tea consumption. Results from this study indicated that the residue of tolfenpyrad can be reduced by proper field management, manufacturing and brewing processes, where field dissipation and brewing were key steps to minimize its risks. Data of this study could also provide guidance for rational application of tolfenpyrad in tea plantations.

Enantioselectivity of indoxacarb during the growing, processing, and brewing of tea: Degradation, metabolites, and toxicities.

Chiral pesticides are unique hazardous materials. Here, we systematically studied the potentially harmful products of enantioselective indoxacarb degradation throughout tea growth, processing, and brewing and tested their toxicity to tea geometrid larvae and honeybees. The half-lives of S-indoxacarb and R-indoxacarb during tea growth were 2.6 d and 3.3 d, respectively. There was a trend toward the production of S-indoxacarb from R-indoxacarb. The degradation products IN-JT333, IN-MK638, IN-MF014, and IN-KG433 were also characterized in tea growth and processing and detected. IN-JT333, previously known as a direct insecticidal compound produced by the enzymatic transformation of indoxacarb in insects, was first found in plant samples. The fixation and rolling of green tea and the rolling of black tea were the most important steps that affected indoxacarb and its degradation products. The leaching rates of R-indoxacarb and S-indoxacarb were slightly higher in green tea than in black tea. The maximum leaching rates of IN-MK638 and IN-MF014 during the brewing process reached 89.9% and 94.1%, respectively. Contact toxicity tests with honeybees and tea geometrid larvae in the lab showed that the relative toxicities of the compounds could be ranked as follows: S-indoxacarb > indoxacarb (3S + 1R) ≫ R-indoxacarb. TEST toxicity predictions showed that relative toxicities were ranked IN-KG433 > indoxacarb > IN-JT333 > IN-MK638 > IN-MF014. The toxicity of the degradation product IN-KG433 is higher than that of indoxacarb itself, and its maximum leaching rate is as high as 88.2%. It therefore transfers readily from processed tea to the tea infusion during the brewing process. These findings indicate the need to pay attention to the risk of metabolites and enantiomeric differences and provide new, comprehensive insight into the risk factors for indoxacarb in tea and are relevant to the study of other chiral pesticides.