[Rapid determination of 15 N-nitrosamines in air-dried yak meat using one-step QuEChERS-gas chromatography-triple quadrupole mass spectrometry].

A method based on gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) coupled with one-step QuEChERS technique was developed for the simultaneous determination of 15 N-nitrosamines in air-dried yak meat. The hydration volume, extraction solvent, extracting salt, and cleaning material were optimized according to the characteristics of the N-nitrosamines and sample matrix. The optimized conditions were as follows: 10 mL of purified water for sample hydration, acetonitrile as the extraction solvent for the sample after hydration, 4.0 g of anhydrous MgSO4 and 1.0 g of NaCl as extracting salts, 500 mg of MgSO4+25 mg of C18+50 mg of PSA as cleaning materials. Favorable recoveries of the 15 N-nitrosamines were obtained when the extraction solution was incompletely dried. Thus, the final extract was dried to below 0.5 mL under a mild nitrogen stream and then redissolved to 0.5 mL with acetonitrile. After filtration, 200 µL of the sample was transferred to an autosampler vial for GC-MS/MS analysis. The 15 N-nitrosamines were determined using GC-MS/MS on a DB-HeavyWAX column (30 m×0.25 mm×0.25 µm) with an electron impact ion source in multiple-reaction monitoring (MRM) mode, and quantified using an external standard method. Under the optimized experimental conditions, the results showed that the calibration curves exhibited good linearities for the 15 N-nitrosamines, with correlation coefficients (r2) greater than 0.9990. The limits of detection (LODs) and the limits of quantification (LOQs) ranged from 0.05 to 0.20 µg/kg and from 0.10 to 0.50 µg/kg, respectively. At spiked levels of 1LOQ, 2LOQ, and 10LOQ, the average recoveries were 79.4%-102.1%, 80.6%-109.5%, and 83.0%-110.6%, respectively, and the relative standard deviations were in the range of 0.8%-16.0%. The low matrix effects of the 15 N-nitrosamines indicated the high sensitivity of the proposed method. The method was applied to detect representative commercial air-dried yak meat samples obtained using different processing techniques. Seven N-nitrosamines, including N-nitrosodimethylamine, N-nitrosodiisobutylamine, N-nitrosodibutylamine, N-methyl-N-phenylnitrous amide, N-ethyl-N-nitrosoaniline, N-nitrosopyrrolidine, and N-nitrosodiphenylamine were detected in all samples. The average contents of the seven N-nitrosamines was 0.08-20.18 µg/kg. The detection rates and average contents of the N-nitrosamines in cooked air-dried yak meat samples were higher than those in traditional raw air-dried yak meat samples. Compared with the manual QuEChERS method, the one-step QuEChERS method developed integrated the extraction and clean-up procedures into one single run, and the detection efficiency was considerably improved. The developed method is simple, rapid, highly sensitive, and insusceptible to human errors. Thus, it is useful for the determination of N-nitrosamines in air-dried yak meat and can be extended to the qualitative and quantitative analysis of N-nitrosamines in other meat products. It also provides method support and a data reference for the general determination of N-nitrosamines, which is of great significance for food safety.

A computational and experimental study of cis-trans isomeric pesticides based on collision-induced dissociation of high-resolution mass spectrometry.

RATIONALE: Pesticide isomers are widely available in agricultural production and may vary widely in biological activity, potency, and toxicity. Chromatographic and mass spectrometric analysis of pesticide isomers is challenging due to structural similarities. METHODS: Based on liquid chromatography time-of-flight mass spectrometry, identification of cis-trans isomeric pesticides was achieved through retention time, characteristic fragment ions, and relative abundance ratio. Furthermore, theoretical and basic research has been conducted on the differences in characteristic fragment ions and their relative abundance ratios of cis-trans isomers. On the one hand, the cleavage pathways of six cis-trans isomers were elucidated through collision-induced dissociation to explain different fragment ions of the isomers. On the other hand, for those with the same fragment ions but different abundance ratios, energy-resolved mass spectrometry combined with computational chemical density functional theory in terms of kinetics, thermodynamics, and bond lengths was employed to explain the reasons for the differences in characteristic fragment ions and their abundance ratios. RESULTS: A high-resolution mass spectrometry method was developed for the separation and analysis of cis-trans isomers of pesticides in traditional Chinese medicine Radix Codonopsis, and six pesticide isomers were distinguished by retention time, product ions, and relative abundance ratios. The limits of quantification of the six pesticides were up to 10 µg/kg, and the linear ranges of them were 10-200 µg/kg, with coefficients of determination (R2) > 0.99, which demonstrated the good linearity of the six pesticides. The recoveries of the pesticides at spiked concentrations of 10, 20, and 100 µg/kg reached 70-120% with relative standard deviations ≤20%. CONCLUSIONS: It was demonstrated that the application of the method was well suited for accurate qualitative and quantitative analysis for isomers with different structures, which could avoid false-negative results caused by ignoring other isomers effectively.

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.

Magnetic graphitized carbon black based on crystal growth method combined with high-resolution mass spectrometry for screening of 300 pesticide residues in Radix Codonopsis and Angelica sinensis.

In this study, a high-throughput method for analyzing 300 pesticide residues in Radix Codonopsis and Angelica sinensis was established by liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-Q-TOF/MS) using iron tetroxide loaded graphitized carbon black magnetic nanomaterial (GCB/Fe3O4) as the purification material. It was optimized that saturated salt water and 1 % acetate acetonitrile were used as the extraction solution, then the supernatant was purified with 2 g anhydrous CaCl2 and 300 mg GCB/Fe3O4. As a result, 300 pesticides in Radix Codonopsis and 260 in Angelica sinensis achieved satisfactory results. The limits of quantification of 91 % and 84 % of the pesticides in Radix Codonopsis and Angelica sinensis reached 10 µg/kg, respectively. The matrix-matched standard curves ranging from 10 to 200 µg/kg were established with correlation coefficients (R) above 0.99. The pesticides meeting SANTE/12682/2021 accounted for 91.3 %, 98.3 %, 100.0 % and 83.8 %, 97.3, 100.0 % of the total pesticides added in Radix Codonopsis and Angelica sinensis respectively, which were spiked at 10, 20,100 µg/kg. The technique was applied to screen 20 batches of Radix Codonopsis and Angelica sinensis. Five pesticides were detected, three of which were prohibited according to the Chinese Pharmacopoeia (2020 Edition). The experimental results showed that GCB/Fe3O4 coupled with anhydrous CaCl2 exhibited good adsorption performance and could be used for sample pretreatment of various pesticide residues in Radix Codonopsis and Angelica sinensis. Compared with the reported methods for determining pesticides in traditional Chinese medicine (TCM), the proposed method has the advantage of less time-consuming in the clean-up procedure. Furthermore, as a case study on root TCM, this approach may serve as a reference for other TCM.

A liquid chromatography-time-of-flight/mass spectrometry method for analysis of pesticides and transfer behavior in Radix Codonopsis and Angelica sinensis decoctions.

The safety of traditional Chinese medicine (TCM) has garnered considerable interest worldwide. In this study, a high-throughput method for the determination of 255 pesticide residues in decoctions of Radix Codonopsis and Angelica sinensis was developed using liquid chromatography-time-of-flight/mass spectrometry. The methodological verification demonstrated the accuracy and reliability of this method. The frequently detected pesticides in Radix Codonopsis and Angelica sinensis were determined to build a correlation between pesticide properties and the transfer rate of pesticide residues in their decoctions. Water solubility (WS) with a higher correlation coefficient (R) made a significant contribution to the accuracy of the transfer rate prediction model. The regression equations for Radix Codonopsis and Angelica sinensis were T = 13.64 log WS + 10.56 with a correlation coefficient (R) of 0.8617 and T = 10.66 log WS + 25.48 with a correlation coefficient (R) of 0.8072, respectively. This study provides preliminary data on the potential risk of exposure to pesticide residues in Radix Codonopsis and Angelica sinensis decoctions. Furthermore, as a case study on root TCM, this approach may serve as a model for other TCMs.

One-Pot Controllable Assembly of a Baicalin-Condensed Aptamer Nanodrug for Synergistic Anti-Obesity.

The rapid, simple and low-cost preparation of DNA micro-nano-architectures remain challenging in biosensing and therapy. Polymerase chain reaction (PCR)-driven DNA micro-nano-flowers are used to construct a nanosized baicalin-compressed-aptamer-nanodrug (bcaND) via one-pot assembly for targeted and synergistic anti-obesity. In the design, the tailored Adipo-8 (tAdi-8) overhang in the PCR amplicon displays anti-obesity targeting activity, while the baicalin loaded in the bcaND by embedding the amplicon plays a three-fold role as a lipid-lowering factor, bcaND size compressor, and uncoupling protein-1 (UCP1)-raised thermogenic activator. The ingenious bcaND represents an advanced multifunctional nanomaterial capable of adjusting the morphology at an optimal 400/1 molar ratio of Mg2+ to phosphate groups, compressing the size from 2.699 µm to 214.76 nm using 1 mg/mL baicalin at a temperature of 70 °C, an effective payload with amplicons of up to 98.94%, and a maximum baicalin load of 86.21 g/g DNA. Responsive release in acidic conditions (pH 5.0) occurs within 72 h, accelerating thermogenesis via UCP1 up-regulation by 2.5-fold in 3T3-L1-preadipocytes and 13.7-fold in the white-adipose-tissue (WAT) of mice, targeting adipocytes and visceral white adipose tissue. It plays an efficient synergistic role in obesity therapy in vitro and in vivo, providing a new direction for DNA self-assembly nanotechnology.

The double flower variant of yellowhorn is due to a LINE1 transposon-mediated insertion.

As essential organs of reproduction in angiosperms, flowers, and the genetic mechanisms of their development have been well characterized in many plant species but not in the woody tree yellowhorn (Xanthoceras sorbifolium). Here, we focused on the double flower phenotype in yellowhorn, which has high ornamental value. We found a candidate C-class gene, AGAMOUS1 (XsAG1), through bovine serum albumin sequencing and genetics analysis with a Long Interpersed Nuclear Elements 1 (LINE1) transposable element fragment (Xsag1-LINE1-1) inserted into its second intron that caused a loss-of-C-function and therefore the double flower phenotype. In situ hybridization of XsAG1 and analysis of the expression levels of other ABC genes were used to identify differences between single- and double-flower development processes. These findings enrich our understanding of double flower formation in yellowhorn and provide evidence that transposon insertions into genes can reshape plant traits in forest trees.

Advanced screening and tailoring strategies of pesticide aptamer for constructing biosensor.

The rapid development of aptamers has helped address the challenges presented by the wide existed pesticides contaminations. Screening of aptamers with excellent performance is a prerequisite for successfully constructing biosensors, while further tailoring of aptamers with enhanced activity greatly improved the assay performance. Firstly, this paper reviewed the advanced screening strategies for pesticides aptamers, including immobilization screening that preserves the native structures of targets, non-immobilized screening based on nanomaterials, capillary electrophoresis-systematic evolution of ligands by exponential enrichment (CE-SELEX), virtual screening in silico, high-throughput selection, and rational secondary library generation methods, which contributed significantly to improve the success rate of screening, reduce the screening time, and ensure aptamer binding affinity. Secondly, the precise tailoring strategies for pesticides aptamers were modularly elaborated, containing deletion, splitting, elongation, and fusion, which provided various advantages like cost-efficiency, enhanced binding affinity, and new derived functional motifs. Thirdly, the developed aptamer-based biosensors (aptasensors) for pesticide detection were systematically reviewed according to the different signal output modes. Finally, the challenges and future perspectives of pesticide detection are discussed comprehensively.

Residual levels and dietary exposure risk assessment of banned pesticides in fruits and vegetables from Chinese market based on long-term nontargeted screening by HPLC-Q-TOF/MS.

The negative impact of banned pesticides is of special importance for their high toxicity. In this study, nationwide screening of banned pesticides in 37462 fruit and vegetable samples was carried out from 2012 to 2018 using a self-developed HPLC-Q-TOF/MS technique. The dietary exposure risks associated with the banned pesticides were assessed. The results showed that 66.62 % of the samples were detected at least one pesticide. Among the pesticide-positive samples, a total of 18 banned pesticides were detected in 1798 samples for 1896 times. The risk assessment revealed that 11.71 % of the positive detections exceeded the safety limits and posed an unacceptable risk, while 37.29 % of the positive detections posed acceptable risks. According to the screening and assessment results, two national maps were presented to show the total detection ratios of the banned pesticides and the unacceptable risks of dietary exposure. It should be noted that omethoate had higher residual concentration, unacceptable risk frequency and unacceptable risk proportion. This is the first nationwide comprehensive report on screening and risk assessment banned pesticides.

Risk assessment of carbofuran residues in fruits and vegetables at the Chinese market: A 7-year survey.

The United Nations designated 2021 as the International Year of Fruits and Vegetables (IYFV), with the goal of educating populations regarding the role of such produce in nutrition, food safety, and overall health. Carbofuran is a highly toxic insecticide and nematocide, and its use to treat fruit trees, vegetables, tea, and medicinal herbs is thus prohibited. However, carbofuran residues are still detectable via LC-Q-TOF/MS in fruit and vegetable samples collected from 138 sites in 31 regions. In the present study, carbofuran levels were sampled at 1388 sampling sites in 31 regions (provinces, autonomous regions, and municipalities) not including Hong Kong, Macao, or Taiwan. In total, over 36,000 samples (including 12,547 samples of 41 kinds of fruits and 23,785 samples of 83 kinds of vegetables) were randomly collected from supermarkets and farmer's markets. These data were used to conduct a risk assessment pertaining to dietary carbofuran exposure through the consumption of fruits and vegetables. In total, carbofuran residues were detectable in 2.0% of fruits and 2.3% of vegetables. Risk assessments indicated that the intake of fruits and vegetables harboring carbofuran residues did not pose a chronic health risk. However, peaches, grapes, sweet peppers, celery, Chinese chives, leaf lettuce, spinach, small rape, mustard greens, cucumbers, watermelons, Chinese wolfberry leaves, wax gourds, snap beans, bitter melons, green Chinese vegetables, lettuce, shallot, cowpeas, eggplants, tomatoes, tangerines, summer squash, oranges, lemons, Chinese cabbage, peppers, and strawberries were associated with an unacceptable acute risk to both children and adults. Moreover, crown daisies, nectarines, citrus fruits, pitayas, melons, kale, cabbages, milk Chinese cabbage, carrots, and melons were associated with an unacceptable acute risk to children. Substantial acute risk to children and adults was observed for fruits and vegetables from surveyed regions other than Inner Mongolia, Yunnan, Liaoning, Fujian, Xinjiang, and Hubei. Together, these data provide a foundation for future research aimed at the management of carbofuran residues in fruits and vegetables in an effort to better protect consumer health.

Multiple Recognition-Based Sensor for Pesticide Residues.

The use of pesticides is gradually increasing to improve the yield and quality of crops. However, excessive pesticide use has led to a dramatic pollution increase in the environment and agricultural products, posing severe human health risks. Therefore, rapid, sensitive pesticide detection is essential. Various pesticides detection methods and products have been developed in recent years. This brief review summarized the point-of-care testing (POCT) detection of pesticides based on multiple recognition, including protein-, aptamer-, nanomaterial-, and macrocycle-based recognition. The review aimed to address the growing demands for regulating and destroying pesticides or other adverse agriculture-related applications in the real world.

PRIAS: An Intelligent Analysis System for Pesticide Residue Detection Data and Its Application in Food Safety Supervision.

Pesticide residue is a prominent factor that leads to food safety problems. For this reason, many countries sample and detect pesticide residues in food every year, which generates a large amount of pesticide residue data. However, the way to deeply analyze and mine these data to quickly identify food safety risks is still an unresolved issue. In this study, we present an intelligent analysis system that supports the collection, processing, and analysis of detection data of pesticide residues. The system is first based on a number of databases such as maximum residue limit standards for the fusion of pesticide residue detection results; then, it applies a series of statistical methods to analyze pesticide residue data from multiple dimensions for quickly identifying potential risks; it uses the Apriori algorithm to mine the implicit association in the data to form pre-warning rules; finally, it applies Word document automatic generation technology to automatically generate pesticide residue analysis and pre-warning reports. The system was applied to analyze the pesticide residue detection results of 42 cities in mainland China from 2012 to 2015. Application results show that the system proposed in this study can greatly improve the depth, accuracy and efficiency of pesticide residue detection data analysis, and it can provide better decision support for food safety supervision.

Rapid Screening of ß-Agonists in Animal Hair by Thermal Desorption Electrospray Ionization Mass Spectrometry.

BACKGROUND: Even though the use of ß-agonists in livestock has been banned in many countries, ß-agonists abuse is still out of control owing to time-consuming and complicated determination techniques. OBJECTIVE: This study applied ambient thermal desorption electrospray ionization mass spectrometry (TD-ESI/MS) as a new strategy for rapidly screening seven ß-agonists. As it does not require pretreatment, this method allows on-site and real-time detection. METHOD: Samples were collected directly using a simple metal probe. Analytes on the probe were desorbed and ionized by TD-ESI, after which analyte ions were detected using a triple quadrupole mass analyser. RESULTS: The results showed that a thermal desorption temperature of 320°C and nebulizer pressure of 3 psi demonstrated the highest sensitivity. Excellent linear relationships were obtained in concentrations ranging from 10 to 400 µg/kg. The limit of detection of the method was 1-10 µg/kg with RSDs of 7.2-14.6%. A positive sample was verified using HPLC coupled with triple quadrupole tandem mass spectrometry, consistent with the results from TD-ESI/MS. CONCLUSION: This method was the first to apply TD-ESI/MS to rapid analyse ß-agonists in livestock hair and was proven to be accurate, fast, and environmentally friendly. Because qualitative screening for each analysis was completed within approximately 1 min, the method could contribute to preventing non-compliance in the flow of animal-derived food to the market. HIGHLIGHTS: This method was a promising method for the rapid screening of ß-agonists in livestock hair at any time of breeding without imposing any harm to animal which proven to be a rapid, in situ, and non-destructive detection technique without any pretreatment.

Automated QuEChERS for the determination of 482 pesticide residues in Radix codonopsis by GC-Q-TOF/MS and LC-Q-TOF/MS.

A rapid procedure for the determination of 482 pesticide residues in Chinese Materia Medica by GC-Q-TOF/MS and LC-Q-TOF/MS (379 pesticides for LC, 327 pesticides for GC, and 226 pesticides for both) was developed. Radix codonopsis was chosen as the matrix for verification, and a comparative study on the QuEChERS sample preparation was carried out, between a fully automated workstation and manual operation, in terms of limits of quantitation, recovery rate and RSD at 3 spiked levels of 10 µg kg-1, 20 µg kg-1 and 100 µg kg-1. In the linear range of each pesticide in a concentration range of 5-100 µg L-1, the linear correlation coefficients R2 of 85% of the pesticides for GC and 88% for LC were equal to or greater than 0.990. Taking recovery 70-120% and RSD ≤ 20% as the satisfactory standard, the automated workstation performed better at 10 µg kg-1 and 20 µg kg-1 than manual operation, and the numbers of satisfactory pesticides of GC & LC were 401 and 418 for the automated approach, and 378 and 400 for manual, while the two approaches were almost even at 100 µg kg-1, 421 vs. 424. Besides, the automated workstation presented lower RSD (more pesticides ≤10%) and better recovery quality (more pesticides within 90-110%). Following the method verification, 50 Radix codonopsis samples purchased from local markets were prepared with the automated workstation and analyzed by GC and LC-Q-TOF/MS. 18 pesticides were detected in 38 samples, one of which was a highly toxic pesticide. The automated QuEChERS workstation can handle 40 samples in one cycle within 6 hours, and realize whole-process automation covering from samples after "weighing" to "injection into vials". The batch-to-batch, day-to-day, and lab-to-lab consistency and 24 × 7 workability of the automated solution have demonstrated a promising and ideal replacement for manual operation in sample preparation.

Simultaneous determination and risk assessment of highly toxic pesticides in the market-sold vegetables and fruits in China: A 4-year investigational study.

This study investigated the levels of highly toxic pesticides (HTPs) in 6554 vegetable and fruit samples from 31 regions of China, along with the associated risk of dietary exposure for the population between 2014 and 2017. 18 HTPs were detected in 325 (4.96%) samples, and the levels of HTPs in 103 (1.57%) samples were found to be higher than the maximum residue limits (MRLs) of China. The rate of detection of HTPs in six types of vegetables and fruits, in a decreasing order, was found to be as follows: eggplant (8.84%) >grape (5.58%) >tomato (5.43%) >cucumber (5.43%) >pear (3.12%) >apple (2.30%). The level of contamination of HTPs was found to be higher in vegetables compared with fruits. The vegetable and fruit samples with the highest percentages of HTPs exceeding MRLs were found in eggplants from Guangxi (20%) and grapes from Inner Mongolia (12.5%), respectively. Both, the average target hazard quotient (THQ) of a single highly toxic pesticide (HTP) and the average hazard index (HI) of the mixture of HTPs for adults and children from vegetables and fruits from the 31 regions were found to be less than one. Omethoate, carbofuran, ethoprophos, triazophos, and phorate were identified as the major contributors to the average HI for vegetables, and carbofuran, ethoprophos, omethoate, phorate, and phosphamidon were identified as the primary contributors to the average HI for fruits. The results of this study revealed that HTPs in vegetables and fruits did not cause any significant chronic risk of dietary exposure. The detection of HTPs exceeding MRLs in some of the samples implied that appropriate management guidelines for HTPs should be implemented to protect the health of the consumers.

Screening of 439 Pesticide Residues in Fruits and Vegetables by Gas Chromatography-Quadrupole-Time-of-Flight Mass Spectrometry Based on TOF Accurate Mass Database and Q-TOF Spectrum Library.

Because of its unique characteristics of accurate mass full-spectrum acquisition, high resolution, and fast acquisition rates, GC-quadrupole-time-of-flight MS (GC-Q-TOF/MS) has become a powerful tool for pesticide residue analysis. In this study, a TOF accurate mass database and Q-TOF spectrum library of 439 pesticides were established, and the parameters of the TOF database were optimized. Through solid-phase extraction (SPE), whereby pesticides are extracted from fruit and vegetable substrates by using 40 mL 1% acetic acid in acetonitrile (v/v), purified by the Carbon/NH2 SPE cartridge, and finally detected by GC-Q-TOF/MS, the rapid analysis of 439 pesticides in fruits and vegetables can be achieved. The methodology verification results show that more than 70 and 91% of pesticides, spiked in fruits and vegetables with concentrations of 10 and 100 µg/kg, respectively, saw recoveries that conform to the European Commission's criterion of between 70 and 120% with RSD ≤20%. Eighty-one percent of pesticides have screening detection limits lower than 10 µg/kg, which makes this a reliable analysis technology for the monitoring of pesticide residues in fruits and vegetables. This technology was further validated for its characteristics of high precision, high speed, and high throughput through successful detection of 9817 samples during 2013-2015.

Screening of 485 Pesticide Residues in Fruits and Vegetables by Liquid Chromatography-Quadrupole-Time-of-Flight Mass Spectrometry Based on TOF Accurate Mass Database and QTOF Spectrum Library.

This paper uses the LC-quadrupole-time-of-flight MS technique to evaluate the behavioral characteristics of MS of 485 pesticides under different conditions and has developed an accurate mass database and spectra library. A high-throughput screening and confirmation method has been developed for the 485 pesticides in fruits and vegetables. Through the optimization of parameters such as accurate mass number, time of retention window, ionization forms, etc., the method has improved the accuracy of pesticide screening, thus avoiding the occurrence of false-positive and false-negative results. The method features a full scan of fragments, with 80% of pesticide qualitative points over 10, which helps increase pesticide qualitative accuracy. The abundant differences of fragment categories help realize the effective separation and qualitative identification of isomer pesticides. Four different fruits and vegetables-apples, grapes, celery, and tomatoes-were chosen to evaluate the efficiency of the method at three fortification levels of 5, 10, and 20 µg/kg, and satisfactory results were obtained. With this method, a national survey of pesticide residues was conducted between 2012 and 2015 for 12 551 samples of 146 different fruits and vegetables collected from 638 sampling points in 284 counties across 31 provincial capitals/cities directly under the central government, which provided scientific data backup for ensuring pesticide residue safety of the fruits and vegetables consumed daily by the public. Meanwhile, the big data statistical analysis of the new technique also further proves it to be of high speed, high throughput, high accuracy, high reliability, and high informatization.

Discrimination of botanical origins for Chinese honey according to free amino acids content by high-performance liquid chromatography with fluorescence detection with chemometric approaches.

BACKGROUND: The contents of 18 free amino acids in 87 Chinese honey samples from four botanical origins (linden, acacia, vitex and rape) were determined by developing a high-performance liquid chromatography with fluorescence detector (HPLC-FLD) method with an in-loop automated pre-column derivatization. The free amino acid profiles of these samples were used to construct a statistical model to distinguish honeys from various floral origins. RESULTS: The average contents of all free amino acids in linden honey were lower than in the other three types of honey. Phenylalanine was particularly useful in the present study because its average content in vitex honey was far higher than in any other honey samples. There is no doubt that both phenylalanine and tyrosine can be considered as the marker free amino acid in Chinese vitex honey. Principal component analysis (PCA) was conducted based on 15 free amino acids and showed significant differences among the honey samples. The cumulative variance for the first two components was 80.62%, and the four principal components can explain 94.18% of the total variance. In the two first component scores, the honey samples can be separated according to their botanical origins. Cluster analysis of amino acid data also revealed that the botanical origins of honey samples correlated with their amino acid content. Back-propagation artificial neural network (BP-ANN) and naïve Bayes methods were employed to construct the classification models. The results revealed an excellent separation among honey samples according to their botanical origin with 100% accuracy in model training for both BP-ANN and naïve Bayes. CONCLUSION: It indicated that the free amino acid profile determined by HPLC-FLD can provide sufficient information to discriminate honey samples according to their botanical origins. © 2016 Society of Chemical Industry.

High-Throughput Analytical Techniques for the Determination of the Residues of 653 Multiclass Pesticides and Chemical Pollutants in Tea, Part VII: A GC-MS, GC-MS/MS, and LC-MS/MS Study of the Degradation Profiles of Pesticide Residues in Green Tea.

GC-MS, GC-tandem MS (MS/MS), and LC-MS/MS were used to mathematically define the degradation profiles of pesticide residues in two field trials. Nineteen pesticides were studied in the first field trial and 11 in the second. The results of the field trials demonstrated that the degradation profiles of pesticide residues in green tea can be described with power functions to successfully estimate the amount of time, following pesticide application, pesticide residues appearing in tea in concentrations at and/or above the maximum residue limit (MRL) decrease to concentrations below the MRL. Stability tests on green tea samples stored at room temperature were conducted to determine whether pesticide-incurred green tea samples prepared according to the method used in the field trials would be suitable for the preparation of reference standards for laboratory-proficiency testing trials. This paper reports the results of a GC-MS, GC-MS/MS, and LC-MS/MS study, as well as the suitability of the samples prepared under these conditions for use as pesticide reference standards in tea analysis.