Advanced analytical method of nereistoxin using mixed-mode cationic exchange solid-phase extraction and GC/MS

Simultaneous determination of nereistoxin insecticides in foods of animal origins by combining pH-dependent reversible partitioning with hydrophilic interaction chromatography-mass spectrometry

Although nereistoxin insecticides (NIs) are banned for animal husbandry operations, they are still used because of their high insecticidal activities. Therefore, a reliable residue analysis method for the simultaneous detection of cartap, bensultap, thiocyclam, and nereistoxin in foods of animal origins, including beef, pork, chicken, milk, and eggs, was developed using hydrophilic interaction liquid chromatography-mass spectrometry (HILIC-LC-MS/MS). The NIs were extracted with an acidic cysteine and formate buffer solution and hydrolyzed to nereistoxin. The molarity and pH of the buffer were optimized at 20 mM and 3, respectively, to keep the pH of the extracts at 4-5. pH-dependent acid-base partitioning coupled with salting-out-assisted liquid-liquid extraction using acetonitrile was performed for purification and for the direct introduction of the extracts to LC. The optimal pH values were 5 and 9 for the acid-base partitioning. Nereistoxin quantitation was achieved with consistent column retention (RSD < 0.6%) and a high degree of separation (N > 10⁶). The matrix-dependent method limit of quantitation was 2 μg nereistoxin/kg, and the calibration curve showed good linearity (R² > 0.998). The recovery efficiencies were in the range of 89.2-109.9% with relative standard deviations less than 10%, and matrix effects did not exceed ± 10%, which satisfied the criteria outlined in the European SANTE/12682/2019 guidelines.

Ultrahigh sensitivity nitrogen-doping carbon nanotubes-based metamaterial-free flexible terahertz sensing platform for insecticides detection

With the rapid advances in terahertz (THz) spectroscopy, metamaterial-free THz sensors have been of importance due to efficient cost, high sensitivity and overcoming the limited tunability of the optical constants of metals. Here, a metamaterial-free and flexible THz sensor based on nitrogen-doping carbon nanotubes (N-CNTs) coupled with signal-enhancing Au NPs was proposed for detecting nereistoxin-related insecticides (NRIs). Sensitivity and selectivity for NRIs detection have been realized over the range of 3.3-100 μg/L with good linear fitting (R² ≥ 0.9003) and LOD was 1.33 μg/L. Accuracy was validated by the recovery rates of 105.87-109.75% of NRI in spiked food-matrix sample. These results indicated the developed signal-enhancing THz method, validated by LC-MS/MS, exhibited high sensitivity and simplicity detection, which has noteworthy potential for applications in food safety and environment monitoring.

Development, optimization, and validation of a method for detection of cartap, thiocyclam, thiosultap-monosodium, and thiosultap-disodium residues in plant foods by GC-ECD

A method was developed for the simultaneous determination of four nereistoxin-related pesticides, viz. cartap, thiocyclam, thiosultap-monosodium, and thiosultap-disodium, in 20 plant foods. The samples were extracted using a hydrochloric acid solution containing cysteine hydrochloride, derivatized to nereistoxin under alkaline conditions, and analyzed by gas chromatography with electron capture detector. The average recoveries of the method were 72-108%, with relative standard deviations (RSDs) of 0.3-14.7% (n = 1200, p < 0.05). The intermediate precision and reproducibility experiments using established methods were also carried out. All the results passed the Cochrane and Grubbs tests (n = 2400, p < 0.05). The RSDs of intermediate precision and RSDs of reproducibility among laboratories were in the ranges 1.7-10.9% and 2.4-15.3% (n = 2400, p < 0.05), respectively, indicating that the accuracy and precision of the method are satisfactory. This method can be used to detect nereistoxin-related pesticides in plant foods.

Marine Origin Ligands of Nicotinic Receptors: Low Molecular Compounds, Peptides and Proteins for Fundamental Research and Practical Applications

The purpose of our review is to briefly show what different compounds of marine origin, from low molecular weight ones to peptides and proteins, offer for understanding the structure and mechanism of action of nicotinic acetylcholine receptors (nAChRs) and for finding novel drugs to combat the diseases where nAChRs may be involved. The importance of the mentioned classes of ligands has changed with time; a protein from the marine snake venom was the first excellent tool to characterize the muscle-type nAChRs from the electric ray, while at present, muscle and α7 receptors are labeled with the radioactive or fluorescent derivatives prepared from α-bungarotoxin isolated from the many-banded krait. The most sophisticated instruments to distinguish muscle from neuronal nAChRs, and especially distinct subtypes within the latter, are α-conotoxins. Such information is crucial for fundamental studies on the nAChR revealing the properties of their orthosteric and allosteric binding sites and mechanisms of the channel opening and closure. Similar data are provided by low-molecular weight compounds of marine origin, but here the main purpose is drug design. In our review we tried to show what has been obtained in the last decade when the listed classes of compounds were used in the nAChR research, applying computer modeling, synthetic analogues and receptor mutants, X-ray and electron-microscopy analyses of complexes with the nAChRs, and their models which are acetylcholine-binding proteins and heterologously-expressed ligand-binding domains.

Marine Natural Products: The Important Resource of Biological Insecticide

Due to the unique environmental conditions and vast territory, marine habitat breeds more abundant biological resources than terrestrial environment. Massive marine biological species provide valuable resources for obtaining a large number of natural products with diverse structure and excellent activity. In recent years, new breakthroughs have been made in the application of marine natural products in drug development. In addition, the use of marine natural products to develop insecticides and other pesticide products has also been widely concerned. Targeting marine plants, animals, and microorganisms, we have collected information on marine natural products with insecticidal activity for nearly decade, including alkaloids, terpenes, flavonoids and phenols fatty acids, peptides, and proteins, et al. In addition, some active crude extracts are also included. This review describes the insecticidal activities of marine natural products and their broad applications for future research in agriculture and health.

A laboratory study on dissipation and risk assessment of the proinsecticide thiocyclam and its metabolite nereistoxin in tomato using liquid chromatography high resolution mass spectrometry

Reduced pesticides use, alongside increased organic farming, has created a need for new biological products, such as thiocyclam, to control pests. Thiocyclam has scarcely been studied, making the study of its degradation in fruits and vegetables, such as tomatoes, an urgent requirement. To monitor thiocyclam metabolites in tomato, dissipation studies were carried out using a liquid chromatography-Orbitrap mass spectrometry (UHPLC-Orbitrap MS) method for 60-days after foliar application. Thiocyclam was not persistent (DT₅₀ < 15 days), but nereistoxin - its primary metabolite - remained present in the tomatoes for >60 days. Four nereistoxin metabolites, detected at low concentrations (<100 µg/kg), were also monitored. This is the first time a study has provided dissipation patterns for thiocyclam and nereistoxin. The results obtained suggest revising the legislation concerning these compounds is required. Toxicological studies must also be carried out because there is no toxicity data currently for thiocyclam or nereistoxin.

An electroanalytical platform for nereistoxin-related insecticide detection based on DNA conformational switching and exonuclease III assisted target recycling

In this work, an electroanalytical platform for nereistoxin (NRT)-related insecticide detection is proposed on the basis of NRT induced DNA conformational switching and exonuclease III (Exo III) assisted target recycling. NRT-related insecticides were first hydrolyzed and converted into NRT with two thiol groups (-SH). Then, a cytosine-Ag+-cytosine (C-Ag+-C) mismatched base pair was adopted to induce a blunt-ended hairpin configuration of HP DNA. In the presence of converted NRT, it could take up Ag+ from HP DNA to change its conformation from a hairpin to single-stranded structure (HP ssDNA). Thereafter, the obtained HP ssDNA was further hybridized with an H1 hairpin probe on the electrode surface to trigger the Exo III cleavage process, releasing HP ssDNA for recycling leaving the G-quadruplex fragment of H1, which was used for hemin/G-quadruplex complex formation. The reversible redox reaction of Fe(iii)/Fe(ii) of hemin gave a remarkable electrochemical response for quantitative determination of the NRT-related insecticides. As an analytical model, a low detection limit of 3.9 ng L-1 and a wide linear range of 0.01-1500 μg L-1 with excellent selectivity were achieved for cartap detection. The proposed method also displayed great applicability for cartap detection in agricultural products.

A high photoluminescence sensor for selective detection of cartap based on functionalized VBimBF4B ionic liquid-strengthened sulfur-doped carbon nanodots

A photoluminescence sensor based on functionalized room temperature ionic liquid-strengthened sulfur-doped carbon nanodots is developed for real-time monitoring of cartap.

Multiwalled Carbon Nanotube for One-Step Cleanup of 21 Mycotoxins in Corn and Wheat Prior to Ultraperformance Liquid Chromatography⁻Tandem Mass Spectrometry Analysis

One-step solid-phase extraction (SPE) using a multiwalled carbon nanotube (MWCNT) for simultaneous analysis of 21 mycotoxins, including nine trichothecenes, zearalenone (ZEN) and its derivatives, four aflatoxins, and two ochratoxins, in corn and wheat was developed. Several key parameters affecting the performance of the one-step SPE procedure—types of MWCNT, combinations with five sorbents (octadecylsilyl (C₁₈), hydrophilic–lipophilic balance (HLB), mixed-mode cationic exchange (MCX), silica gel, and amino-propyl (NH₂)), and filling amounts of the MWCNTs—were thoroughly investigated. The combination of 20 mg carboxylic MWCNT and 200 mg C₁₈ was proven to be the most effective, allowing the quantification of all analyzed mycotoxins in corn and wheat. Under the optimized cleanup procedure prior to ultraperformance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) analysis, the method was validated by analyzing samples spiked at the limit of quantification (LOQ), two-times LOQ, and 10-times LOQ. Satisfactory linearity (r² ≥ 0.9910), high sensitivity (LOQ in different ranges of 0.5–25 μg L⁻¹), good recovery (75.6–110.3%), and acceptable precision (relative standard deviation (RSD), 0.3–10.7%) were obtained. The applicability of the method was further confirmed using raw samples of corn and wheat. In conclusion, the established method was rapid, simple and reliable for simultaneous analysis of 21 mycotoxins in corn and wheat.

Rapid Colorimetric Detection of Cartap Residues by AgNP Sensor with Magnetic Molecularly Imprinted Microspheres as Recognition Elements

The overuse of cartap in tea tree leads to hazardous residues threatening human health. A colorimetric determination was established to detect cartap residues in tea beverages by silver nanoparticles (AgNP) sensor with magnetic molecularly imprinted polymeric microspheres (Fe₃O₄@mSiO₂@MIPs) as recognition elements. Using Fe₃O₄ as supporting core, mesoporous SiO₂ as intermediate shell, methylacrylic acid as functional monomer, and cartap as template, Fe₃O₄@mSiO₂@MIPs were prepared to selectively and magnetically separate cartap from tea solution before colorimetric determination by AgNP sensors. The core-shell Fe₃O₄@mSiO₂@MIPs were also characterized by FT-IR, TEM, VSM, and experimental adsorption. The Fe₃O₄@mSiO₂@MIPs could be rapidly separated by an external magnet in 10 s with good reusability (maintained 95.2% through 10 cycles). The adsorption process of cartap on Fe₃O₄@mSiO₂@MIPs conformed to Langmuir adsorption isotherm with maximum adsorption capacity at 0.257 mmol/g and short equilibrium time of 30 min at 298 K. The AgNP colorimetric method semi-quantified cartap ≥5 mg/L by naked eye and quantified cartap 0.1–5 mg/L with LOD 0.01 mg/L by UV-vis spectroscopy. The AgNP colorimetric detection after pretreatment with Fe₃O₄@mSiO₂@MIPs could be successfully utilized to recognize and detect cartap residues in tea beverages.

Sonochemical preparation of gold nanoparticles for sensitive colorimetric determination of nereistoxin insecticides in environmental samples

A simple colorimetric method using gold nanoparticles (AuNPs) was developed as an efficient strategy for specific and sensitive detection of insecticides that are analogs of nereistoxin (NRT). The AuNPs were synthesized by a surfactant-free sonochemical reaction with ultrasonication at 430 kHz. A color change occurred in the presence of NRT because the AuNPs aggregated if they were coated with a small amount of thioctic acid (TA). At a pH of around 5, the TA adsorbed on the AuNPs was deprotonated, whereas NRT was protonated (NRT-H⁺). Adsorption of NRT-H⁺ onto the TA-coated AuNPs surface would decrease the surface charge of the AuNPs, and this resulted in aggregation. Because the aggregation of the TA-coated AuNPs could not be induced by amine compounds without thiol groups, this provided a surface-limited aggregation mechanism for specific sensing of NRT. The absorbance at 700 nm was dependent on the concentration of NRT, and the calibration curve was linear over the concentration range 85 nM (12 ng/mL) to 1000 nM (140 ng/mL). The applicability of the proposed method to detection of trace levels of NRT in environmental water samples was successfully demonstrated using a simple liquid-liquid reverse extraction technique.

Nontargeted Screening and Determination of Sulfonamides: A Dispersive Micro Solid-Phase Extraction Approach to the Analysis of Milk and Honey Samples Using Liquid Chromatography-High-Resolution Mass Spectrometry

A simple, rapid, sensitive, selective, and environmentally friendly method, based on a dispersive micro solid-phase extraction approach (dispersive micro SPE) coupled with liquid chromatography-high-resolution mass spectrometry (LC-HRMS), was established for the analysis of sulfonamides in honey and milk. An efficient nontargeted screening strategy was designed to discover and identify known and unknown sulfonamides in honey and milk using full-MS/all ion fragmentation (AIF) mass spectrometry acquisition mode. The experimental parameters and conditions of dispersive micro SPE on extraction efficiency were optimized in detail. Under the optimized conditions, the dispersive micro SPE method showed a low limit of detection (LOD) for the targeted sulfonamides ranging from 0.003 to 0.2 μg/L in milk and from 0.01 to 1 μg/kg in honey with the recoveries of the analytes between 68.8 and 115.8%. Compared with the reported methods, improvements in convenience, low cost, and environmental friendliness were obtained in this study.

Patterns of drugs & poisons in southern area of South Korea in 2014

The southern area of South Korea consists of three parts; Busan, Ulsan and Gyeongsangnam-do. Busan Institute of National Forensic Service (NFS) performed about 50,000 cases throughout the southern area in 2014, occupying over 15% of total cases covered by NFS. In this study, patterns of drugs and poisons in the southern area of South Korea were investigated. The investigation was carried out by the laboratory information management system of NFS between January and December of 2014. As results, a total of 606 autopsy cases were performed by Busan Institute of NFS in 2014. Among them, 15 cases were determined as drug intoxication or poisons as the cause of death, taking up 2.5% of total cases: 5 cases of intoxication by drugs, 5 by agricultural pesticides, 3 by illicit drugs, and 1 each by detergents and chemical substances. A total of 108 drugs in postmortem bloods were detected from the autopsy cases, and the top 5 drugs were chlorpheniramine, tramadol, diazepam, zolpidem and lidocaine. Meanwhile, a total of 1,728 cases were submitted for illicit drug testing in 2014. Among them, hair was the most common type of specimens, and the rate of positive detection of methamphetamine from the hair, urine, and seized materials in the southern area was over 50% in all cases, indicating that this is the most commonly abused drug in South Korea. A total of 12 types of novel psychoactive substances (NPSs) were detected in the southern area in 2014; 10 were identified as synthetic cannabinoids and 2 as alkyl nitrites.

A single-step solid phase extraction for the simultaneous determination of 8 mycotoxins in fruits by ultra-high performance liquid chromatography tandem mass spectrometry

A simple and rapid extraction procedure for the simultaneous determination of eight mycotoxins (Alternaria toxins, ochratoxin A, patulin, citrinin) in a variety of fruit matrices has been developed using ultra high performance liquid chromatography coupled to tandem mass spectrometry. The procedure involves a one-step cleanup using homemade solid phase extraction (SPE) cartridges. By comparative evaluation among six various adsorbents (C18, PSA, HLB, MCX, Silica, NH2), the combination of MCX and NH2 was found to provide the most effective cleanup, removing the greatest number of matrix interferences and also allowing the quantification of all analyzed mycotoxins in fruits. The optimized extraction conditions including acidified aqueous acetonitrile and an additional salt-out step using NaCl were employed before SPE cleanup. Method validation was performed by analyzing samples spiked at three levels (LOQ, 2 LOQ and 10 LOQ). Four fruits including apple, sweet cherry, tomato and orange fruits were selected, and accuracy (recovery%), precision (RSD%), limits of quantification (LOQ), linearity and matrix effect were evaluated during validation. Matrix-matched linearity with correlation coefficients ≥ 0.9921 was established in the range of 5-200 ng mL(-1) for patulin and 1-200 ng mL(-1) for other mycotoxins, respectively. Recoveries between 74.2% and 102.4% and relative standard deviations lower than 4.7% were obtained for all tested fruits. The matrix effect observed was low (≤ ± 17%) in all three fruit matrixes with the exception of orange, for which strong ion suppression was observed for alternariol (25.3%), ochratoxin A (31.6%) and citrinin (40.3%). Therefore, matrix-matched calibration was used for a correct quantification in order to compensate for matrix effect. The limits of quantification (LOQ), ranging from 1 to 5 μg kg(-1) depending on mycotoxins type, were always lower than maximum permitted levels for every regulated mycotoxin by the current European legislation.