Evaluation of supercritical fluid chromatography accurate mass spectrometry for neonicotinoid compounds determination in wine samples

Regenerated SERS substrate based on Ag/AuNPs-TiO2-oxidized carbon cloth for detection of imidacloprid

Imidacloprid (IMI) are widely used in modern tea industry for pest control, but IMI residues pose a great threat to human health. Herein, we propose a regeneration metal-semiconductor SERS substrate for IMI detection. We fabricated the SERS sensor through the in-situ growth of a nano-heterostructure incorporating a semiconductor (TiO2) and plasmonic metals (Au, Ag) on oxidized carbon cloth (OCC). Leveraging the high-density hot spots, the formed Ag/AuNPs-TiO2-OCC substrate exhibits higher enhancement factors (1.92 × 108) and uniformity (RSD = 7.68%). As for the detection of IMI on the substrate, the limit of detection was lowered to 4.1 × 10-6 μg/mL. With a hydrophobic structure, the Ag/AuNPs-TiO2-OCC possessed excellent self-cleaning performance addressing the limitation of single-use associated with traditional SERS substrates, as well as the degradation capability of the substrate under ultraviolet (UV) light. Accordingly, Ag/AuNPs-TiO2-OCC showcases outstanding SERS sensing and regenerating properties, making it poised for extensive application in the field of food safety assurance.

Amino-functional magnetic covalent organic framework as an effective adsorbent for the determination of neonicotinoids in food samples

Recently, covalent organic frameworks have gained popularity in sample pretreatment. However, the application of covalent organic frameworks in the enrichment of hydrophilic compounds remains a challenge. Thus, a functionalized magnetic covalent organic framework equipped with amino groups was constructed using a bottom-up functionalization strategy. Considering the advantages of this novel adsorbent such as high porosity, large adsorption capacity, and hydrophilic surface, a sensitive magnetic solid-phase extraction coupled with high-performance liquid chromatography-tandem mass spectrometry method was established for the effective determination of neonicotinoids. This method exhibited good linearities with correlation coefficients ranging from 0.9983 to 0.9995, low detection limits in the range 0.003-0.009 ng g-1 and 0.001-0.013 ng mL-1, and limits of quantification in the range 0.010-0.031 ng g-1 and 0.004-0.044 ng mL-1. Furthermore, satisfactory repeatability with relative standard deviations ≤ 6.7% and spiked recoveries between 82.3 and 99.8% were obtained. This work not only provided a promising adsorbent for the sensitive determination of trace-level neonicotinoids but also represented a unique insight for effective enrichment of super hydrophilic hazards.

Fabrication of magnetic magnesium oxide cleanup adsorbent for high-throughput pesticides residue analysis coupled with supercritical fluid chromatography-tandem mass spectrometry

A rapid and accurate analytical method was established for multiple pesticide residues in complex matrices based on magnetic dispersive solid phase extraction (d-SPE) and supercritical fluid chromatography-tandem mass spectrometry (SFC-MS/MS). To develop an efficient magnetic d-SPE method, magnetic adsorbent modified with magnesium oxide (Fe₃O₄-MgO) was prepared via layer-by-layer modification and used as cleanup adsorbent for removal of interferences that contain a large number of hydroxyl or carboxyl groups in the complex matrix. The obtained Fe₃O₄-MgO coupled with 3-(N,N-Diethylamino)-propyltrimethoxysilane (PSA) and octadecyl (C18) were used as d-SPE purification adsorbents and their dosages were systematically optimized with Paeoniae radix alba as the matrix model. Combined with SFC-MS/MS, rapid and accurate determination of 126 pesticide residues in the complex matrix was achieved. Further systematic method validation showed good linearity, satisfactory recovery, and wide applicability. The average recoveries of the pesticides at 20, 50, 80, and 200 μg kg^-1 were 110, 105, 108, and 109%, respectively. The proposed method was applied to complex medicinal and edible root plants, such as Puerariae lobate radix, Platycodonis radix, Polygonati odorati rhizoma, Glycyrrhizae radix, and Codonopsis radix. The average recoveries of the pesticides at 80 μg kg^-1 in these matrices were 106, 106, 105, 103, and 105%, respectively with an average relative standard deviation range of 8.24-10.2%. The results demonstrated the feasibility and wide matrix applicability of the proposed method, which is promising for pesticide residue analysis in complex samples.

A Simple and Novel Sensor for the Determination of Acetamiprid Based on Its Reducing Effect on the Chemiluminescence of S, N-CQDs in CH3CN-H2O2 System

A simple and novel method for the determination of acetamiprid in water samples is suggested. The method is based on the reducing effect of acetamiprid on the chemiluminescence intensity of new sulfur and nitrogen co-doped carbon dots (S, N-CQDs) in an acetonitrile-hydrogen peroxide (CH₃CN-H₂O₂) system. The possible mechanism was investigated, and it was found that S, N-CQDs react with (¹O₂)₂*, produced from the CH₃CN-H₂O₂ reaction, leading to excited state S, N-CQDs, which deactivate to the ground state by photon emission. Acetamiprid diminishes the chemiluminescence (CL) intensity by competing with S, N-CQDs. The CL intensity reduction is proportional to the concentration of acetamiprid. S, N-CQDs were easily prepared by a hydrothermal method. Under the optimal conditions, a linear range of 2.5 - 25.0 μg L^-1 with a detection limit (3σ) of 0.4 μg L^-1 was obtained. This method was successfully applied to the determination of trace amounts of residual pesticides in water samples.

Combination of polyurethane and polymethyl methacrylate thin films as a microextraction sorbent for rapid adsorption and sensitive determination of neonicotinoid insecticides in fruit juice and tea by ultra high performance liquid chromatography with tandem mass spectrometry

An economical and effective thin film microextraction (TFME) for simultaneous analysis of ten neonicotinoid insecticides and metabolites in fruit juice and tea, was developed based on the combination of polyurethane (PU) and polymethyl methacrylate (PMMA) films as the sorbent followed by ultra high performance liquid chromatography with tandem mass spectrometry. The PU/PMMA composite was evidenced to possess rapid adsorption and strong accumulation towards neonicotinoids compared with the films used alone. A series of parameters were optimized, and the agitation mode, film size, ionic strength, desorption solvent and sample pH were found to dominate the microextraction process rather than the extraction temperature, agitation time and sample volume. The thin films are cost effective and efficient for single use analysis, but still can be reused at least 8 times with no significant loss in performance. The ten neonicotinoids were measured with good recoveries (81.1-107.9%), high enrichment factors (up to 135), low limits of detection (0.001-0.1 µg L^-1), and wide linearity range (1-500 µg L^-1, r²>0.9981) in fruit juice (apple, lemon, and pomegranate) and tea (green tea and black tea) samples. The proposed method was successfully applied to commercial fruit and tea drinks, and no samples were tested positive on target neonicotinoids. The PU/PMMA based TFME has shown great potential as an alternative to exhaustive extraction techniques for routine screening of trace neonicotinoids in fruit juice and tea by simplifying the analytical procedure, shortening the operation time, and lowering the material expense.

Liquid chromatography versus supercritical fluid chromatography coupled to mass spectrometry: a comparative study of performance for multiresidue analysis of pesticides

Abundant studies have been published evaluating different parameters of reverse-phase liquid chromatography (LC) and supercritical fluid chromatography (SFC), both coupled to electrospray (ESI)/mass spectrometry (MS) for pesticide residue analysis. However, there is a lack of a comprehensive comparative study that facilitates deep knowledge about the benefits of using each technique. In the present study, the same mass spectrometer was used coupled to both liquid and supercritical fluid chromatographies with a multiresidue method of 215 compounds, for the analysis of pesticide residues in food samples. Through the injection of the spiked extracts, separate experiments were conducted. A study of the optimum ion source temperature using the different chromatography modes was performed. The results were evaluated in terms of sensitivity with tomato, leek, onion, and orange as representative fruit and vegetable matrices. The compounds which reported the highest area values in each chromatography were evaluated through their substance groups and polarity values. The impact of matrix effects obtained in tomato matrix was similar for both cases; however, SFC clearly showed better results in analyzing matrices with a higher number of natural co-extracted compounds. This can be explained by the combination of two effects: (i) chromatography separation and (ii) ion source efficiency. The chromatographic elution presented different profiles of matrix components, which had diverse impact on the coelution with the analytes, being more beneficial when SFC was used in the matrices studied. The data showed that the best results obtained in SFC are also related to a higher ionization efficiency even when the ESI emitter tip was not optimized for SFC flow. In the present study a comprehensive evaluation of the benefits and drawbacks of these chromatography modes for routine pesticide residue analysis related to target compounds/commodities is provided.

A review of retention mechanism studies for packed column supercritical fluid chromatography

The packed column supercritical fluid chromatography has risen as a promising alternative separation technique to the conventional liquid chromatography and gas chromatography. Although the packed column supercritical fluid chromatography has many advantages compared to other chromatographic techniques, its separation mechanism is not fully understood due to the complex combination effects of many chromatographic parameters on separation quality and the lacking of global strategies for studying separation mechanisms. This review aims to provide recent information regarding the chromatographic behaviors and the effects of the parameters on the separation, discuss the results, and point out the remaining bottlenecks in the packed column supercritical fluid chromatography retention mechanism studies.

Comparison of Pesticide Residue Levels in Red Wines from Canary Islands, Iberian Peninsula, and Cape Verde

In this work, the QuEChERS method coupled to liquid chromatography-time-of flight-mass spectrometry and gas chromatography-triple quadrupole-mass spectrometry were applied for the evaluation of pesticide residues and risk assessment in red wines. The methodologies were successfully validated for 173 pesticides. Recovery values were in the range 75-100% for almost all pesticides and limits of quantification were between 2.60 and 21.39 µg/kg, which are in good agreement with the maximum residue limits (MRLs) established by the European Commission for pesticides in wine grapes. Finally, the analysis of 84 red wine samples from the Canary Islands, the Iberian Peninsula, and Cape Verde was carried out, which found the presence of 31 pesticide residues. However, the risk assessment disclosed that despite the large number of pesticides and the concentrations found, which in some cases exceeded the MRLs, the consumption of these wines, without considering a possible cumulative effect, does not entail a risk to the consumers.