Detection Of Pesticide Residues Research Articles

MOF-derived multi-"hotspot" 3D Au/MOF-808 (Zr) nanostructures as SERS substrates for the ultrasensitive determination of thiram.

Aconvenient self-assembly methodis proposed for synthesis of 3D Au/MOF-808 (Zr) composite nanostructures with a cerium metal-organic framework loaded with gold nanoparticles. We combine adsorption properties of MOF materials with surface plasmon resonance of noble metals to construct hotspot-dense 3D Au/MOF-808 (Zr) SERS substrates, by using a two-step method of solvothermal and reduction reactions. The results show that optimal SERS substrates are obtained from a volume ratio of gold nanoparticles to MOF-808 (Zr) solution of 4:1 and a self-assembly time of 2h. Rhodamine 6G (R6G) is used as a molecular probe to characterize and analyze SERS properties of substrates of 3D Au/MOF-808 (Zr) prepared under the optimal process conditions, where the substrates are capable to detect R6G concentrations down to 10-10 M with a relative standard deviation of 8.81%. Finally, we applied the SERS substrates of 3D Au/MOF-808 (Zr) to the detection of pesticide thiram, and establish a quantitative determination method. 3D Au/MOF-808 (Zr) provides a sensitive detection of thiram in lake water by SERS with a detection limit of 1.49 × 10-9 M. Application tests show that a SERS enhancement factor of the MOF-based SERS substrates for the detection of thiram can be significantly increased to 5.91 × 105. Thus, the above results indicate that such substrate has high sensitivity, good adsorption, homogeneity, and reproducibility, which can be extended for sensitive detection of pesticide residues in food and environment.

Quantifying pesticide residues in food matrices using statistical methods

Traditional techniques for pesticide residues detection and quantification in food using mass spectrometry often require the analysis of standards for each compound, leading to time-consuming and laborious procedures, especially considering that these methods usually involve hundreds of pesticides to be targeted. This paper presents a novel approach to compound quantitation, where multiple target compounds can be accurately quantified using few predictor compounds, significantly reducing the experimental time and minimizing resource requirements. For this purpose, data on detector response which encompassed calibration slopes of a total of 96 pesticide standards on GC-MS/MS and 66 standards on LC-MS/MS, over a period of 4 years, were collected. Two fundamental statistical techniques, Pearson correlation and linear regression, were used to create a predictive model, which accuracy was further evaluated using R-square, adjusted R-square, and Root Mean Square Error (RMSE). Four predicted compounds for the LC dataset and seven predicted compounds for GC dataset were identified, and various predictor combinations were considered. A linear regression model was developed using predictor combinations to estimate the calibration slope of each of the target compound. This model was applied for the quantitation of several pesticide residues in food samples. The results validated the model’s high accuracy.

Occurrence and Risk Assessment of Pesticides, Phthalates, and Heavy Metal Residues in Vegetables from Hydroponic and Conventional Cultivation.

Hydroponic cultivation of fresh produce is gaining popularity worldwide, but few studies have provided a comparative assessment of hydroponic and conventional soil-based vegetables. In this study, we analyzed a series of hazardous chemicals, including 120 pesticides, 18 phthalates (PAEs), and 2 heavy metals (lead and cadmium) in four vegetable commodities (lettuces, celeries, tomatoes, and cucumbers) from hydroponic and conventional soil-based cultivation. Our study showed that at least one pesticide was present in 84% of the conventionally grown samples, whereas only 30% of the hydroponic samples contained detectable pesticide residues. Regarding the total PAE concentrations, there was no significant difference between conventional and hydroponic vegetables. The lead and cadmium residues in conventionally cultivated vegetables were significantly higher than in those produced from hydroponic cultivation. Lead is the primary heavy metal pollutant across all vegetable samples. The hazard index (HI) values of the hydroponic and conventional vegetables were 0.22 and 0.64, respectively. Since both values are below one, the exposure to these hazardous chemicals through consumption of the studied vegetables may not pose a significant health risk. The HI values also suggested that the health risks of eating hydroponic vegetables are lower than for conventional soil-based vegetables.

Research on Soil Pesticide Residue Detection Using an Electronic Nose Based on Hybrid Models

At present, the electronic nose has became a new technology for the rapid detection of pesticides. However, the technique may misidentify them for samples that have not been involved in training. Therefore, a hybrid model based on unsupervised and supervised learning was proposed for the first time in this paper. The model divided the detection process of soil pesticide residues into two steps: (1) an unsupervised machine learning method was used to identify whether the soil was contaminated with pesticides; (2) when the soil was contaminated with pesticides, a supervised classifier was further used to predict the types of pesticides in the soil. The experimental results showed that the model had a recognition accuracy of 99.3% and 99.27% for whether the soil was contaminated with pesticides and the pesticide type of the contaminated soil, respectively, with a detection time of 0.03 s. The results revealed that the proposed hybrid model can quickly and comprehensively reflect the soil information’s status.

Citizens protein project: A self-funded, transparent, and concerning report on analysis of popular protein supplements sold in the Indian market.

Protein powders, including those containing herbal and dietary supplements such as vitamins, minerals, and other natural or synthetic ingredients, can be associated with hepatotoxicity. Protein supplements are often mislabeled and deceptive in their contents. In this self-funded transparent study, we extensively analyzed popular protein supplements in India to identify potential hepatotoxic substances based on industrial standards. All products underwent extensive analysis, including total protein content, fungal aflatoxin detection, pesticide residue estimation, heavy metal quantification, steroid detection, and complete organic and inorganic profiling, according to industry standards. Most protein supplements did not meet the labeled and advertised protein content, while certain brands surpassed the stated levels, raising concerns about potential "protein/amino-spiking." In addition, the major brands contained detectable fungal toxins and pesticide residues. Furthermore, many major formulations contained harmful heavy metals such as lead and arsenic, and some featured hepatoxic herbal extracts, particularly green tea extract, turmeric, Garcinia cambogia, and Ashwagandha. Indian-made products were inferior to those manufactured by multinational companies. The presence of various potentially toxic compounds, such as cycloheptatriene, benzene derivatives, toluene, and isopropyl alcohol, within a nonstandardized and unregulated diverse ingredient mix added to the overall concern. We demonstrate that the protein-based herbal and dietary supplement industry requires stringent scrutiny, regulation, and basic safety studies before being marketed. Manufacturers must consider reducing "ingredient complexities" of their protein powders to prevent adverse interactions between herbal and nonherbal components in consumers. Manufacturers must avoid using known toxic ingredients to reduce the avoidable disease burden within the public community.

[Determination of 222 pesticide residues in olive oil by fully automatic QuEChERS pre-treatment instrument coupled with gas chromatography-quadrupole-time-of-flight mass spectrometry].

Pesticide residues may be present in olive oil because pesticides are applied to olive trees during their cultivation and growth for pest prevention and some of these pesticides are not easily degraded. Studies on pesticide residues in olive oil have mainly focused on the detection of single types of pesticide residues, and reports on the simultaneous detection of multiple pesticide residues are limited. At present, hundreds of pesticides with different polarities and chemical properties are used in practice. In this study, an analytical method based on fully automatic QuEChERS pretreatment instrument coupled with gas chromatography-quadrupole time-of-flight mass spectrometry (GC-QTOF-MS) was established for the rapid determination of 222 pesticide residues in olive oil. The effects of acetonitrile acidification concentration, n-hexane volume, oscillation time, centrifugation temperature, and purification agent on the determination of the 222 pesticide residues were investigated. First, ions with good responses and no obvious interference were selected for quantification and characterization. The purification process was then developed by setting the parameters of the fully automatic QuEChERS pretreatment instrument to optimal values. The sample was extracted with acetonitrile containing 2% formic acid, and the supernatant was purified by centrifugation in a centrifuge tube containing 400 mg N-propylethylenediamine (PSA), 400 mg octadecylsilane-bonded silica gel (C18), and 1200 mg anhydrous magnesium sulfate. The purified solution was blown dry with nitrogen and then fixed with ethyl acetate for instrumental analysis. Finally, a matrix standard solution was used for quantification. The method was validated in terms of matrix effects, linear ranges, limits of detection (LODs) and quantification (LOQs), accuracies, and precisions. The results showed that 86.04% of the 222 pesticides had linear ranges of 0.02-2.00 μg/mL, 10.81% had linear ranges of 0.10-2.00 μg/mL, and 3.15% had linear ranges of 0.20-2.00 μg/mL. The pesticide residues showed good relationships within their respective linear ranges, and the correlation coefficients (R2) were greater than 0.99. The LODs of all tested pesticides ranged from 0.002 to 0.050 mg/kg, and their LOQs ranged from 0.007 to 0.167 mg/kg. Among the 222 pesticides determined, 170 pesticides had LOQs of 0.007 mg/kg while 21 pesticides had LOQs of 0.017 mg/kg. At the three spiked levels of 0.2, 0.5, and 0.8 mg/kg, 79.58% of all tested pesticides had average recoveries of 70%-120% while 65.92% had average recoveries of 80%-110%. In addition, 93.54% of all tested pesticides had relative standard deviations (RSDs, n=6)<10% while 98.35% had RSDs (n=6)<20%. The method was applied to 14 commercially available olive oil samples, and seven pesticides were detected in the range of 0.0044-0.0490 mg/kg. The residues of fenbuconazole, chlorpyrifos, and methoprene did not exceed the maximum limits stated in GB 2763-2021. The maximum residual limits of molinate, monolinuron, benalaxyl, and thiobencarb have not been established. The method utilizes the high mass resolution capability of TOF-MS, which can improve the detection throughput while ensuring good sensitivity. In addition, high-resolution and accurate mass measurements render the screening results more reliable, which is necessary for the high-throughput detection of pesticide residues. The use of a fully automatic QuEChERS instrument in the pretreatment step reduces personnel errors and labor costs, especially when a large number of samples must be processed, thereby offering significant advantages over other approaches. Moreover, the method is simple, rapid, sensitive, highly automatable, accurate, and precise. Thus, it meets requirements for the high-throughput detection of pesticide residues in olive oil and provides a reference for the development of detection methods for pesticide residues in other types of oils as well as the automatic pretreatment of complex matrices.

Determination of twelve neonicotinoid pesticides in chili using an improved QuEChERS method with UPLC-Q-TOF/MS

In this study, a QuEChERS method based on citrate was developed and utilized for the analysis of twelve neonicotinoid pesticides in fresh red chilies, fresh green chilies, and dried chilies, coupled with ultra-high performance liquid chromatography quadrupole time of flight mass spectrometry (UPLC-Q-TOF/MS). In the sample preparation, acetonitrile containing 1% formic acid was used as the extraction solvent. Anhydrous sodium sulfate replaced the traditional anhydrous magnesium sulfate for water removal, effectively eliminating the issues of salt caking. Graphitized carbon black, octadecyl silica, and primary secondary amine were used as cleaning agents. The method showed good sensitivity, with the limits of quantification below 0.03 mg/kg for fresh chilies and below 0.15 mg/kg for dried chilies. Values of matrix effects ranged from −19.5% to 8.4%, and the recovery was 86.9% - 105.2%. The analytical method provided an effective tool for the high throughput detection of neonicotinoid pesticide residues in multiple chili matrices.

Rapid determination of thiram in lake water using Au/Fe3O4 nanoparticles decorated MOF-867 as efficient surface-enhanced Raman scattering substrate

Rapid determination of pesticide residues in water is of vital importance for human health. However, rapid, reliable, and highly sensitive detection of pesticide residues in water environments remains a challenging issue. In this paper, we prepare Fe3O4/MOF-867 composites using the hot solvent method, and Au+ is reduced to Au NPs by the reducing agent and attached to the film of Fe3O4/MOF-867 composites by the addition of APTES as a linker to synthesize the Au/Fe3O4/MOF-867 SERS substrates. Then, we change the Fe3O4 content and the concentration of the reducing agent to obtain the optimal substrate. The substrate has a detection capability of up to 10-9M for probe molecule R6G and the RSD is less than 5%, which demonstrates that the substrate has excellent SERS effect and reproducibility. In addition, the Au/Fe3O4/MOF-867 SERS substrates have been applied for the determination of thiram in lake water samples, with its limit of detection (LOD) up to 3.8 × 10-10M. The Au/Fe3O4/MOF-867 SERS substrates can quickly and efficiently collect target analytes by magnetic enrichment, have high SERS performance, and have great potential for the rapid and sensitive detection of pesticide residues and other pollutants in the environment.

Quartz fiber supported Ag nano-islands as flexible SERS substrate with stable distributed “hot-spot” in rapid detection of pesticide residue

Island-shaped Ag nanoparticles are prepared under the support platform of quartz fabric by a simple chemical deposition method. The prepared flexible SERS substrate in this study demonstrates highly sensitive, excellent signal reproducibility and stability. The enhancement ability can be adjusted by varying concentration of Ag+ during synthesizing process, which would lead to the variation of size and gaps of Ag nanoparticles, thus affecting the LSPR effect. Moreover, the prepared SERS substrate shows great practical potential in rapid detection of contaminated fruit with different sampling method.

Analysis of carbamate and organophosphorus pesticide in agricultural irrigation water by Liquid Chromatography - Mass Spectrometry

So far, the ultra-trace concentration of pesticide residues in environmental samples has challenged many analytical techniques, which are used to detect simultaneously organophosphorus and carbamate with various polarities. In this study, the OASIS-HLB column was modified by the reagent 1,8-Dihydroxy-2-(4-sulfophenylazo)naphthalene-3,6-disulfonic to enhance the retention of polar pesticides. Both real irrigation water and distilled water samples were applied to validate the determination method of ten carbamates and thirty-eight organophosphorus pesticides all together using LC-MS. According to the results, the linear interval of the method ranged from 1.0 to 100 µg/L, the detection limit was as low as 5.0 µg/L, the relative standard deviations presented less than 8.0%, and the recoveries were ranging between 60% and 112%. Moreover, in the irrigation water samples which were collected in both dry and rainy seasons in ten stations around the agricultural area, five compounds were found, including fenamiphos, terbufos, aldicarb, propoxur, and methiocarb. In the midst of those sampling areas, the Environmental Impact Quotient Field Use Rating of detected pesticide residues presented a high value - 272 at one station, which indicates a high risk for the surrounding environment as well as the local people’s health.

Evaluation of pesticide residues and heavy metals in common food tubers from Nigeria

Pesticide residues and heavy metal content of cassava, yam, cocoyam, potato, water yam and carrot were evaluated by gas chromatography–mass spectrometry and atomic absorption spectroscopy. The detected pesticide residues in the samples were 2,4-dichlorophenoxyacetic acid, glyphosate, hexachlorobenzene (HCB), dichlorobiphenyl, aldrin, endosulfan, profenofos, g-chlordane, carbofuran, biphenyl, heptachlor, lindane and t-Nonachlor. The concentration of HCB ranged between 0.0799 ± 0.06 mg/kg and 0.1596 ± 0.00 mg/kg, which was greater than the permitted maximum limit of 0.5 mg/kg established by the US Environmental Protection Agency. The concentration of aldrin and profenofos detected was lower than the predetermined maximum allowed limits. Endosulfan concentrations in cocoyam (0.2500 mg/kg) and potato (0.3265 mg/kg) were higher than the limits allowed by the Canadian Department of Industrial Research. The heavy metals detected in these samples include cobalt, nickel, lead, manganese, chromium, arsenic and mercury in at least one of the samples evaluated. There was not much difference between the concentration of cobalt in yam (0.036 mg/kg) and the maximum allowed concentration (0.043 mg/kg). Lead was detected in potatoes and carrots but was below detectable concentration in cassava, yam, cocoyam and water yam. Similarly, cocoyam was found to have a significant mercury content (0.658 mg/kg), but mercury content was below detectable concentrations in cassava, yam and water yam.

Sandwich-like CuNPs@AgNPs@PSB SERS substrates for sensitive detection of R6G and Forchlorfenuron

The development of a highly sensitive, synthetically simple and economical SERS substrate is technically very important. A fast, economical, sensitive and reproducible CuNPs@AgNPs@ Porous silicon Bragg reflector (PSB) SERS substrate was prepared by electrochemical etching and in situ reduction method. The developed CuNPs@AgNPs@PSB has a large specific surface area and abundant “hot spot” region, which makes the SERS performance excellent. Meanwhile, the successful synthesis of CuNPs@AgNPs can not only modulate the plasmon resonance properties of nanoparticles, but also effectively prolong the time stability of Cu nanoparticles. The basic performance of the substrate was evaluated using rhodamine 6G (R6G). (Detection limit reached 10−15 M, R2 = 0.9882, RSD = 5.3 %) The detection limit of Forchlorfenuron was 10 μg/L. The standard curve with a regression coefficient of 0.979 was established in the low concentration range of 10 μg/L −100 μg/L. This indicates that the prepared substrates can accomplish the detection of pesticide residues in the low concentration range. The prepared high-performance and high-sensitivity SERS substrate have a very promising application in detection technology.

One-step detection of pesticide residues in vegetables using an inkjet printing-based test card

The overuse of pesticides has seriously threatened human safety and health, while their detection is still limited by complex procedures. An inkjet printable test card was created in this study for the quick and broad screening of organophosphorus (OP) and carbamate (CM) pesticides in one step. To ensure sensitivity and accuracy, slow-release polyvinyl alcohol (PVA) films were used as the printing substrate to separate the reaction system from the acetylcholinesterase (AChE) film. When the pesticide-containing sample was introduced to the test card, the activity of AChE was initially inhibited by pesticide residues. Subsequently, the PVA membrane dissolved, and the remaining AChE reacted with the substrate and chromogenic agent, resulting in the production of yellow products. Therefore, the levels of pesticide residues in the sample can be determined by observing color changes. Experimental results demonstrated that this test card exhibited high sensitivity, stability, and reproducibility. Moreover, this method is quick and straightforward, showing great potential in both commercial and domestic applications.

Raman Spectroscopy-Based Chemometrics for Pesticide Residue Detection: Current Approaches and Future Challenges

Raman Spectroscopy-Based Chemometrics for Pesticide Residue Detection: Current Approaches and Future Challenges

Carboxymethyl chitosan–modified UiO-66 for the rapid detection of fenpropathrin in grains

Fenpropathrin residues in grain are potentially harmful to humans. Therefore, a fluorimetric lateral flow immunoassay using a zirconium-based organic skeleton (UiO-66) as a signal marker was developed for detecting fenpropathrin. Herein, carboxymethyl chitosan (CMCS) was used to modify UiO-66 and improve its water solubility to facilitate stable binding with sodium fluorescein (NaFL). This resulted in formation of a new fluorescent probe that is more suitable for lateral flow immunoassay (LFIA). The materials were characterized via electron microscopy, Fourier-transform infrared spectroscopy, and powder X-ray diffraction. CMCS and NaFL were successfully bound to UiO-66. Under optimized conditions, the constructed NaFL/UiO-66@CMCS-LFIA exhibited a good linear relationship within the range of 0.98–62.5 μg/L, with a detection limit of 3.91 μg/L. This probe was fourfold more sensitive than traditional colloidal gold nanoparticle-based LFIA. Finally, NaFL/UiO-66@CMCS-LFIA was successfully applied to detect fenpropathrin in wheat and maize samples. The detection limit was 1.56 μg/kg and recoveries ranged from 96.58 % to 118.56 %. This study provides a sensitive, stable, and convenient method for the rapid detection of pesticide residues.

A Rapid and Easy Procedure of Enzyme Biosensor based on Nitrogen-Doped Graphene for Detection of Methyl Parathion in CHM

Methyl parathion (MP), an organophosphorus pesticide that is frequently used to control pests during the planting process of Chinese herbal medicine (CHM), has been used without sufficient control, leading to excessive residues on the surface of CHM, which has a serious impact on the quality and safety of CHM and their preparations. Consequently, it is crucial to carefully control MP during the cultivation, processing, and manufacture of CHM. Based on this, nitrogen-doped graphene (N-Gr) with a high conductivity and chitosan (CS) with good stability were used to modify the glassy carbon electrode (GCE). Subsequently, the prussian blue (PB) with catalytic activity and gold nanoparticles (AuNPs) with excellent biocompatibility were deposited by the electrodeposition method to form the AuNPs/PB/CS@N-Gr/GCE. Then, the acetylcholinesterase (AChE) was effectively immobilized on the electrode surface by covalent bonding between AuNPs and AChE through gold-sulfhydryl bonds. Finally, a rapid and easy procedure of enzyme biosensor (AChE/AuNPs/PB/CS@N-Gr/GCE) for sensitive detection of MP pesticide residues was fabricated. Herein, PB catalyzes the redox reaction of thiocholine, which is produced when acetylthiocholine iodide (ATCHI) undergoes efficient hydrolysis catalyzed by AChE. This process effectively promoted electron transfer, amplifying the sensor’s response signal. After the experimental conditions are optimized, the limit of detection (LOD) for MP is found to be 9.47 × 10−5 μg ml−1. Exhibits a good linear relationship within the concentration range of 1 × 10−3 μg ml−1 ∼ 1 × 101 μg ml−1. Significantly, the fabricated enzyme biosensor excels in swiftly and sensitively detecting trace amounts of MP in real examples. Furthermore, it exhibits robust stability and reproducibility. The excellent performance of this enzyme biosensor not only offers a rapid and easy way to identify and find minute amounts of trace MP pesticide residues in CHM, but also serves as a technical guide for the creation of new, portable, and on-site pesticide residue detection technology for law enforcement.

Determination of pesticide residue in soil samples by molecularly imprinted solid-phase extraction method

Abstract Porous molecularly imprinted polymer (MIP) microspheres were synthesized via iniferter-suspension polymerization method, employing lenacil (LA) as the template molecule and methacrylic acid (MAA) as the functional monomer. The host–guest complexes formed using LA and MAA were characterized by hydrogen nuclear magnetic resonance and ultraviolet–visible absorption spectroscopy. The obtained results showed that the interaction between LA and MAA mainly relied on hydrogen bonding. The surface morphologies and chemical structures of the MIPs were characterized by scanning electron microscopy. MIPs were spherical in shape with a relatively regular sphericity, rough surface structure, and numerous small holes, which significantly reduced the mass transfer resistance of the template molecules and exhibited excellent recognition performance for template molecules. In addition, soil samples were pretreated with solid-phase extraction columns molecularly imprinted with LA, and analyzed by high-performance liquid chromatography. The recoveries of LA, bromacil, and terbacil were up to 89.65%, 53.17%, and 44.63%, respectively. The developed method showed a minimum detection limit of 10–50 µg·mL−1. In view of the continuous increase of public requirements for pesticide residue detection, a versatile pretreatment method was developed that is green, rapid, simple, and can be miniaturized.

Fabrication of a label-free electrochemical immunosensor by functionalized nanofiber membrane for the ultrasensitive detection of quinalphos

The accumulation of quinalphos pesticide in agricultural products have detrimental effects to human body and environment, hence, an efficient and sensitive detection approach is desirable. In this study, a label-free electrochemical immunosensor based on the directly immobilizing nanobody onto functionalized polyvinyl alcohol/gelatin-gold nanoparticles nanofiber membrane (PVA/G-AuNPs NFM) was fabricated. First, a homogeneous PVA/G-AuNPs NFM with multiple-porosity structure and appropriate hydrophilicity was prepared. Then, the electrochemical immunosensor was assembled and under the optimized conditions, the prepared biosensor exhibited good detection performance towards quinalphos with the linear range and limit of detection being 0.06–1000 ng/mL and 50.74 pg/mL (S/N = 3), respectively. Moreover, the sensor presented good specificity, regenerability and stability, maintaining more than 90% activity after 5 times of regeneration and about 90% activity after 6 weeks of storage. Finally, the average recoveries of quinalphos from food samples were 89.68%–110.88% with the coefficient of variation being 1.65%–7.81%, showing good correlation with UPLC-MS/MS (R2 = 0.9859), indicating the accuracy of the proposed electrochemical immunosensor assay. Overall, the label-free electrochemical immunosensor presents a novel approach for the rapid and sensitive detection of quinalphos and other pesticide residues.

Fluorescence spectroscopy detection of carbendazim residue in cucumber juice based on BC

Excessive residues of the carbendazim pesticide in food will cause food safety issues. Particularly, cucumber is one of the common vegetables with carbendazim residues. This study, using fluorescence spectroscopy technology, explored the residues of carbendazim in cucumbers. First, a fluorescence spectrophotometer was used to scan and obtain the three-dimensional fluorescence spectra of carbendazim standard and four carbendazim formulations. Analyzing and comparing their respective fluorescence characteristics, fluorescence peak 1: Ex/Em=245/300–320 nm and fluorescence peak 2: Ex/Em=280/300–320 nm have been identified as the fluorescence characteristic peaks of carbendazim, and the optimal excitation wavelengths Ex=245 nm and Ex=280 nm with carbendazim specificity was screened. Subsequently, two-dimensional fluorescence spectroscopy was performed on the carbendazim and cucumber-carbendazim mixed solutions using the optimal excitation wavelength. In order to obtain more effective two-dimensional spectral data, the original fluorescence spectrum of the cucumber-carbendazim mixed solution was subjected to Blank Correction (BC), significantly reducing the impact of cucumber's own fluorescent characteristics on the carbendazim fluorescent peak in the mixed solution. Polynomial models and linear prediction models were developed based on the concentration of carbendazim and the fluorescence peak intensity values obtained after BC. The detection limit value of carbendazim residues in the cucumber-carbendazim mixed system included the maximum pesticide residue limit specified by national food safety regulations. This research provides valuable data and technical support for efficient detection of pesticide residues in cucumbers.

[Determination of 35 prohibited pesticide residues in Saussurea costus by modified QuEChERS method based on multi-walled carbon nanotubes coupled with gas chromatography-tandem mass spectrometry].

Saussurea costus, a perennial herb belonging to the Asteraceae family, is a vital ingredient in traditional Chinese medicine. Increased demands for the herb have led to its widespread cultivation in China, but the corresponding increase in pesticide use has raised concerns about pesticide residues. Such residues would affect the safety and global market potential of Saussurea costus. Thus, a simple method is crucial to detect pesticide residues. The QuEChERS technique, in combination with gas chromatography-tandem mass spectrometry (GC-MS/MS), is commonly used for residue detection. However, traditional adsorbents may be unable to purify complex herbal mixtures well, affecting accuracy and instrument performance. Choosing suitable purification materials for Saussurea costus samples with complex matrices is of significant importance. This study focused on the detection of 35 prohibited pesticides in Saussurea costus. A rapid detection method was established by combining the QuEChERS technique with GC-MS/MS and utilizing a combination of multiwalled carbon nanotubes (MWCNTs), octadecylsilane-bonded silica gel (C18), and anhydrous magnesium sulfate (MgSO4) as the purification adsorbent. The samples were extracted with acetonitrile, purified by an improved QuEChERS process, subjected to GC-MS/MS analysis in multiple reaction monitoring (MRM) mode, and quantified using the internal standard method. The purification effects of four materials (C18, MWCNTs, N-propyl ethylenediamine (PSA), and graphitized carbon black (GCB)) and their optimal dosages were investigated by considering the matrix characteristics of the samples. An orthogonal experimental design was employed to optimize the ratio of adsorbent combinations, and the optimal adsorbent combination was determined to be 450 mg of MgSO4, 400 mg of C18, and 50 mg of MWCNTs. Matrix effect (ME) evaluation of the S. costus matrix showed that 31 target compounds strongly exhibited matrix-enhancement effects. Thus, matrix-matched calibration was employed in this study. Methodological investigation revealed that the standard curves for the 35 pesticides exhibited good linearity, with correlation coefficients (r2) greater than 0.9970. The average recoveries at three spiked levels ranged from 69.6% to 126.9%, and the relative standard deviations (RSDs) for parallel groups were all less than 10%. The limits of detection (LODs) and quantification (LOQs) ranged from 0.2 to 5.4 μg/kg and from 0.6 to 18.1 μg/kg, respectively. The developed method was used to screen and detect 35 pesticide residues in 20 batches of S. costus samples, and the target compounds were detected in six batches. The proposed method is simple, sensitive, and accurate. Thus, it is suitable for the rapid screening and detection of the 35 pesticide residues in S. costus and provides technical support for the cultivation, production, and quality control of the herb.