A rapid method for detecting bronopol in fresh fish, shrimp, crab, and shellfish samples using liquid chromatography-tandem mass spectrometry.

Fish farming plays a vital role in providing food, nutrition, and employment globally. However, this industry faces security challenges, necessitating the use of fungicides and preservatives, such as bronopol, to increase product yields. Bronopol (2­bromo-2-nitropropan-1,3-diol; CAS:52-51-7) is widely used in various fields, including food production, cosmetics, and, more recently, aquaculture. Currently, there is a limited number of techniques available for detecting bronopol in aquaculture products. This is primarily due to bronopol's instability, susceptibility to degradation, and tendency to form precipitates that pose challenges in extraction from aquaculture products. For this issue, this study presents a comprehensive method for detecting bronopol content in aquaculture tissues using liquid chromatography-tandem mass spectrometry (LC‒MS/MS). The methodology was optimized, involving extraction with Cu-Zn precipitant, cleanup using a small HLB column, separation on a T3 column, and gradient elution with water and acetonitrile mobile phases. The quantitative approach was employed without the use of an internal standard, following the external standard method. The spiked recoveries at 3 fortification levels (0.1, 0.2, and 1 mg/kg) ranged from 87.1 % to 108.1 % with relative standard deviations RSD ≤ 9.0 %. By applying this method to fresh fish, shrimp, crab, and shellfish samples from a local supermarket, no residues of bronopol were detected, ensuring the reliability of the results. The simplicity, rapidity, and high sensitivity of the method make it a suitable alternative to conventional techniques for bronopol detection. Moreover, the successful validation of the method's recovery and precision supports its potential application in monitoring and preventing the misuse of bronopol in aquaculture, thereby safeguarding aquaculture product quality and protecting public health.

Sensitive SERS assay for glyphosate based on the prevention of l-cysteine inhibition of a Au-Pt nanozyme.

Herein, an indirect SERS sensing assay was developed for the determination of glyphosate (Gly) in tap water. The mechanism of detection was based on relieving the inhibitory effect of l-cysteine (l-cys) on a Au-Pt nanozyme by combining Gly with l-cys through divalent copper ions (Cu2+). In this method, a novel nano-chain-like Au-Ag composite with good repeatability was successfully fabricated to detect SERS signals of oxTMB without disturbing TMB Raman signals. Under optimal conditions, the SERS signal intensity of oxTMB (at 1605 cm-1) was proportional to the concentration of Gly. The results showed a good linear response over the concentration ranges of 10 µg L-1 to 1000 mg L-1. The limit of detection and limit of quantitation of Gly were found to be 5 µg L-1 and 10 µg L-1, respectively. In addition, good anti-interference ability against interfering cations and structural analogues deserves to be mentioned. This SERS assay can be used for detection of Gly in tap water that can meet the needs of practical detection.

Assessment of magnetic core-shell mesoporous molecularly imprinted polymers for selective recognition of triazoles residual levels in cucumber.

Functional magnetic nanomaterials based on molecular imprinting technique were successfully prepared on the surface of modified Fe3O4. Transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffractometer, and vibrating sample magnetometry were applied for characterization of the synthesized magnetic nanoparticles. The magnetic molecularly imprinted polymers (MMIPs) exhibited satisfactory magnetic response, specific recognition, and excellent adsorption capacity toward triazoles (maximum adsorption capacity of 9202.9 µg g-1 for triadimefon). The obtained MMIPs were further used as magnetic dispersive solid-phase extraction (MDSPE) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) for detection of 20 triazoles in cucumber spiked at different levels. The mean recoveries were ranged from 79.9% to 110.3% and relative standard deviations (RSDs) were <11.2% (n = 5). Herein, we report a simple, rapid, environmentally friendly, and magnetic stuff recyclable approach for triazoles residual analysis in complicated agricultural products.

Magnetic molecularly imprinted polymers for the detection of aminopyralid in milk using dispersive solid-phase extraction.

A method for dummy molecular imprinting-magnetic dispersive solid-phase extraction (MI-MDSPE) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed for the selective determination of aminopyralid in milk. The magnetic material and polymers were combined via a series of modifications in Fe3O4. Fe3O4@SiO2-NH2@MIP, Fe3O4@SiO2-COOH@MIP and two types of aminopyralid-specific magnetic molecularly imprinted polymers (MMIPs) were prepared on the surface of magnetic nanoparticles modified with amino and carboxyl groups. The morphology and magnetic properties of the polymer were characterized. Fe3O4@SiO2-NH2@MIP exhibits not only good dispersibility and magnetic properties, but also an outstanding recognition pattern to the target analyte. Adsorption experiments demonstrated that Fe3O4@SiO2-NH2@MIP, with a high specific surface area and fast mass transfer rate, had a higher affinity than Fe3O4@SiO2-COOH@MIP towards aminopyralid. Under the optimized MI-MDSPE conditions, the method had good linearity (R 2 > 0.9972), excellent recoveries (83.3-90%), and good precision (relative standard deviations (RSDs) < 12.6%). This method has limits of detection (LOD) and quantification (LOQ) of 0.231 and 0.77 µg kg-1, respectively, indicating that these MMIPs can be used to analyse trace levels of aminopyralid in real samples.

Fabrication of a highly sensitive electrochemical sensor based on electropolymerized molecularly imprinted polymer hybrid nanocomposites for the determination of 4-nonylphenol in packaged milk samples.

Herein, an imprinted electrochemical sensor based on graphene-Au nanoparticles incorporated with molecularly imprinted polymer (MIP) was fabricated for determination of 4-nonylphenol (4-NP). Grafted MIP electropolymerized on nanoscale multilayer films electrode was achieved using 4-NP as a template and P-aminothiophenol as a functional monomer. The electrochemical properties of the MIP nanoscale multilayer membrances were characterized and measured by cyclic voltammetry and differential pulse voltammetry techniques; using ferrocyanide/ferricyanide-redox marker. Several important parameters were optimized and investigated to improve the performance of the sensor. Under the optimized conditions, the developed sensor showed an excellent linear response over the concentration ranges of 50-500 ng mL-1 (4-NP) with a detection limit of 0.01 ng mL-1(S/N = 3). The developed sensor showed a good selective recognition of 4-NP compared with structural analogue, exhibited a good reproducibility and accuracy with long-term stability. At last, the feasibility of the proposed methodology was successfully applied fordetection of 4-NP in milk and its packaging materials.