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In this experiment, we designed an electrochemical sensor using penicillinase (Pen X)‐rhombus porous carbon (RPC) as the detection element and hematoxylin as the indicator to detect low concentrations of penicillin sodium (Pen G). A differential pulse voltammetry (DPV) method was used to detect Pen G in the concentration range of 10–8–10–5 mg·mL–1 under optimal experimental conditions. The results showed that the peak current value and the logarithm of Pen G concentration showed a good linear relationship (R2 = 0.9915), and the LOD was 2.68 × 10–7 mg·mL–1 (S/N = 3). The actual milk samples were detected by the addition method and compared with the high‐performance liquid phase method; no significant difference was found in the detection results. The working electrode prepared by cross‐linking method not only extends the service life of the sensor, but also improves the sensitivity and reproducibility of the sensor. It can also be used to detect the Pen G residue in the actual milk samples repeatedly. Practical Application: In this study, an electrochemical sensor for the rapid detection of penicillin sodium in milk was prepared, which has good sensitivity and fast detection speed. [ABSTRACT FROM AUTHOR]

In recent years, to increase growth rate and prevent infectious diseases, an excessive use of antibiotics in livestock breeding processes has resulted in the presence of antibiotic residues in animal foods. In this experiment, a new kind of electrochemical sensor is prepared based on magnetic mesoporous hollow carbon microspheres (MHM) as a penicillinase (Pen X) adsorption carrier to rapidly detect penicillin sodium (Pen G), named Pen X/MHM/MGCE. The MHM‐adsorbed penicillinase can be separated from the solution by magnetic attraction and fixed on a magnetic glassy carbon electrode by physical adsorption, which is easy to operate and avoids the interference of a crosslinking agent at the active site of the enzyme. A differential pulse voltammetry (DPV) method is used to immerse the working electrode in test samples containing different concentrations of penicillin sodium solution with 0.5 mg/mL oxidized hematoxylin. According to the quantitative relationship between the current value and the concentration of penicillin sodium, the concentration of penicillin sodium in the tested samples can be determined. The detection range of the sensor is 10−8 to 10−2 mg/mL, the linear relationship is good (R2 = 0.9983), and the detection limit (LOD) is 2.655 × 10−7 mg/mL (S/N = 3). The detection of penicillin sodium in milk using a standard addition method shows good recovery. Furthermore, the proposed method has the advantages of a wide detection range, good enzyme immobilization capacity, good precision and stability, convenient cleaning, and recycling of solid materials. Thus, it can successfully achieve rapid detection in milk samples. Practical Application: The sensor provides a low detection limit and high recovery rate of electrode material; therefore, the sensor can realize the rapid and quantitative detection of penicillin sodium in milk. [ABSTRACT FROM AUTHOR]

The generation of guaiacol by Alicyclobacillus acidoterrestris (A. acidoterrestris) in fruit juices negatively affects public health and causes severe environmental pollution. Therefore, the sensitive detection and efficient degradation of guaiacol in real samples are crucial. Here, we develop an electrochemical sensor utilizing a copper single-atom nanozyme (CuN 4 -G) to detect and degrade guaiacol at the picomolar level. Density functional theory (DFT) calculations verify that the bonding electron coupling effect in the CuN 4 -G facilitates rapid electron transfer, enhances electrical conductivity, and provides abundant active sites, thereby leading to exceptional catalytic performance. Moreover, CuN 4 -G demonstrates a K m value similar to that of natural laccase but a higher V max , highlighting its potential as a highly efficient biocatalyst. The CuN 4 -G-based electrochemical sensor achieves a detection from 5 to 50,000 pM for guaiacol, with a 1.2 pM (S/N = 3) detection limit. Additionally, CuN 4 -G-modified electrodes display high selectivity and excellent stability. CuN 4 -G nanozyme can keep its activity in conditions of pH (3–9), temperature (30–90 °C), ionic strength (0–400 mM), and organic solvent (0–50% (v/v)), overcoming the deficiencies of natural enzymes. Furthermore, our electrochemical sensor can not only accurately detect guaiacol, but also degrade it in actual fruit juice samples infected by A. acidoterrestris , demonstrating its potential applications in food and environmental monitoring. [ABSTRACT FROM AUTHOR]

• Magnetic mesoporous carbon was loaded on the magnetic electrode to prepare a sensor. • The selectivity of aptamer-streptomycin controls the electrical signal of reaction. • Molecule modelling reveals that aptamer-streptomycin has the highest affinity. • The sensor exhibits the detection limit of 0.015 nM for streptomycin detection. Exploiting a simple and sensitive sensor to efficiently detect streptomycin (STR) in milk is critical for resolving the harm caused to humans by STR residues. This study reports an electrochemical sensor using magnetic mesoporous carbon materials (MMCM) as a loaded material through magnetic adsorption immobilized on magnetic glassy carbon electrode (MGCE) and adsorbing unlabeled streptomycin aptamer (STP) as the identification element. The sensor can detect STR sensitively with a wide detection range (0.172–17.2 × 103 and 17.2 × 103 –17.2 × 105 nM) and a low detection limit of 0.015 nM. Experimental results revealed that the specific binding of STP with STR on the electrode changed the configuration of STP, thereby causing current change of differential pulse voltammetry curve. Compared with HPLC, this study provides a new method for rapid and sensitive detection of STR in milk (n = 5, 95 % confidence level, RSD＜5%). [ABSTRACT FROM AUTHOR]