To analyze the whole-genome sequences of 67 Salmonella strains from different sources, characterize their carriage profiles of virulence genes and pathogenicity islands, molecular typing and core-genome phylogenetic relationships, and decipher the association networks between mobile genetic elements and virulence genes/plasmids, reveal the virulence-related genetic characteristics at the genomic level.

Whole-genome assembly sequences of 67 Salmonella strains were downloaded from the EnteroBase database. The VFDB database and the CGE online tool were used for virulence gene annotation, virulence island identification and mobile element alignment, respectively. Sankey diagrams were employed to visualize the relationships among strains, virulence genes and plasmids and mobile elements. Multilocus sequence typing and core genome single nucleotide polymorphism phylogenetic analysis were performed via the EnteroBase platform, and data visualization was conducted using the Chiplot online tool.

The 67 bacterial strains comprised a total of 20 kinds of serotypes, with the predominant serotypes being Salmonella typhimurium (29.85%), Salmonella enterica (14.93%) and Salmonella Reiseri(11.94%). A total of 183 virulence genes were identified, of which 56 were present in 100% of all strains, primarily involving Type III secretion systems, fimbriae, regulatory factors and effector proteins. A total of 12 virulence islands were identified, with SPI-1, SPI-2, SPI-3, SPI-5 and SPI-9 present in 100% of the strains. Among mobile genetic elements, various insertion sequences and transposons were closely associated with virulence genes and plasmids, notably, nlpl showed the highest association with MITEEc1. The core genome single nucleotide polymorphism phylogenetic tree classified the strains into 4 major clusters: A, B, C and D. Cluster A was the largest (46 strains), dominated by ST34 and ST11, and exhibited close genetic clustering across provinces; Cluster B contains the ST198 epidemic strain from Kentucky; Clusters C and D represented rare or independent lineages.

This study reveals differences in the distribution of foodborne and environmental Salmonella serotypes. Core virulence factors, such as the Type III secretion system, are highly conserved across all strains. Mobile genetic elements play a key role in the horizontal transmission of virulence genes and plasmids. Phylogenetic analysis provides evidence of cross-regional transmission, particularly indicating a spreading trend of the Kentucky ST198 strain, which requires continuous monitoring.

To establish an anodic stripping voltammetry method based on disposable screen-printed electrodes for the rapid quantitative detection of inorganic arsenic in grain, and systematically validate the proposed method.

Screen-printed electrodes were employed combining with rapid extraction and mild pretreatment methods. The optimal detection conditions were determined by optimizing the electrode geometry, carbon-based ink materials and the concentration of sodium tetrachloroaurate in the working buffer. The method was validated in terms of linear range, limit of detection, limit of quantitation, precision and accuracy. And it was compared with the liquid chromatography-inductively coupled plasma mass spectrometry method in GB 5009.11—2024 National food safety standard-Determination of total arsenic and inorganic arsenic in foods. Finally, the repeatability of the method was verified, and a method for on-site rapid screening was established.

Under the optimized conditions, the method exhibited a good linear relationship within the concentration range of 0.046–0.440 mg/kg, with a determination coefficient (r²) of 0.9991. The limit of detection was 0.018 mg/kg, and the limit of quantitation was 0.062 mg/kg. The spiked recoveries ranged from 85% to 92%, with relative standard deviations of 5.8%–12.4%. No significant difference was observed between the results of this method and those obtained by the GB 5009.11—2024. The paired t-test P for measurements from multiple instruments were all greater than 0.05.

This method is simple to operate, rapid and low-cost, making it suitable for on-site rapid quantitative detection in grain depots and processing enterprises, with good prospects for promotion and application.

To establish a method for the determination of 11 kinds of β-agonists (clenbuterol, ractopamine, salbutamol, terbutaline, cimaterol, clorprenaline, ziprasidone, cimbuterol, bromobutirone, bambuterol, mabutrol) content in pork, beef and pork liver by high performance liquid chromatography-tandem mass spectrometry(HPLC-MS/MS).

After overnight incubation, the samples were extracted with acetonitrile containing 0.5% formic acid, purified by Bond Elut EMR-Lipid dispersive solid-phase extraction (SPE), and then reconstituted with methanol-0.1% formic acid. The sample was separated on a C₁₈ column (2.1 μm×150 mm, 2.7 μm) using methanol-0.1% formic acid as the mobile phase. Gradient elution was performed with electrospray ionization (ESI) positive ion scanning, and quantification was achieved by internal standard method.

The determination coefficient (r²) of the standard curve of 11 kinds of β-agonists in the range of 0.5–25.0 ng/mL was above 0.995. The relative standard deviations (RSDs) of instrument were less than 7.8%. The limit of detection was 0.10 μg/kg. By adding 0.20 μg/kg of the target compounds to the representative matrix, the recovery of the target was 95.0%–110.0% and the precision RSDs were 0.75%–9.53%, so the 0.20 μg/kg was determined as the limit of quantitation. The average recoveries of the target compounds in the representative matrices of pork, beef and pork liver were 78.1%–108.4% at the concentrations of 0.5, 5.0 and 10.0 μg/kg, respectively. The precision RSDs were less than 8.76%. The limit of quantitation and the accuracy of the method were all in line with the requirements of the detection of trace veterinary drug residues.

The method is simple and rapid, with high sensitivity, good recovery and reproducibility, and can be used to determine 11 kinds of β-agonists in animal derived foods.

To establish a method for the determination of 22 kinds of organophosphate esters (OPEs) compounds in fish meat by ultra performance liquid chromatography-tandem mass spectrometry.

Samples were extracted by ultrasonic treatment with 0.1% formic acid-acetonitrile solution, and the extracts were purified through an HLB-Prime solid-phase extraction column. The samples were then dissolved in a nitrogen-blowed 0.5 mL mixture of 50% acetonitrile-0.1% formic acid before detection. The A phase (acetonitrile) and the B phase (2 mmol/L ammonium formate aqueous solution) were used as the mobile phase for gradient elution, with a flow rate of 0.2 mL/min and an injection volume of 2 μL. Multiple reaction monitoring (MRM) mode was employed for detection. The target compounds were separated on an ACQUITY UPLC® BEH C₁₈ chromatographic column (100 mm×2.1 mm, 1.7 μm) and detected via MRM in electrospray positive (18 kinds of OPEs) and negative (4 kinds of OPEs) ion modes, with isotope internal standard quantification.

Through optimization of chromatographic conditions, baseline separation was achieved for all 22 kinds of OPEs compounds. The 22 kinds of OPEs compounds exhibited good linearity within the range of 0.5–50.0 μg/L, with correlation coefficients all greater than or equal to 0.997. The limits of detection were 0.1–0.2 μg/kg, and the limits of quantitation were 0.3–0.6 μg/kg. The spiked recovery rates at low, medium and high concentration levels in fish meat ranged from 77.4% to 109.3%, with relative standard deviations (n=6) ranging from 1.8% to 8.6%. Using the established method, 7 fish meat samples were analyzed, and the detection rate of OPEs was 71.4%, and the residue of triethyl phosphate (TEP) in the sole was 29.60 μg/kg.

The method is simple, reliable, sensitive, reproducible and covers a wide range of OPEs, which is suitable for the detection of OPEs in fish meat.

To establish a method for the determination of 8 kinds of trace disinfection byproducts in water by ion chromatography-tandem mass spectrometry.

After passing through a 0.22 μm hydrophilic filter, water samples were separated on an alkanol quaternary ammonium-type ion chromatography column, passed through a suppressor, and then detected by tandem quadrupole mass spectrometer, using electrospray negative ionization in multiple reaction monitoring mode, and quantifed by the internal standard method.

The 8 kinds of trace disinfection byproducts showed good linearity within their respective ranges, with correlation coefficients all great than or equal to 0.9980. The limits of detection were 0.003–0.100 ng/mL, and the limits of quantitation were 0.01–0.50 ng/mL. Under the optimized conditions, the average spiked recoveries of disinfection byproducts at different concentration levels in various matrix water samples (pure water, finished/tap water, source water and distributed/end-point water) ranged from 85% to 120% (diiodoacetic acid: 60.8%–90.6%), with relative standard deviations of 0.39%–18.80% (iodoacetic acid: 1.82%–20.20%). It was found that when different internal standards were used for quantification, the spiked recoveries of 8 kinds of disinfection byproducts in pure water met the criterion of 80%–120%, but deviations were observed in other water matrices. Therefore, the optimal internal standard for accurate detection was the homologous isotope-labeled internal standard of the compound. The method was applied to analysis real samples in Beijing, and 6 kinds of disinfection byproducts were detected, with the mass concentrations ranging from 0.10 to 46.00 ng/mL.

The method is simple, sensitive and accurate, and is suitable for the determination of disinfection byproducts in drinking water and source water, providing a rapid, simple and accurate approach for practical monitoring of disinfection byproducts in water samples.

To establish a method for determination of 16 kinds of pesticide residues in tea by modified QuEChERS-high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) using carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) and attapulgite (ATP).

Tea samples were extracted with acetonitrile containing 1% acetic acid. After purification with anhydrous magnesium sulfate, primary secondary amine, MWCNTs-COOH and ATP, the extract was filtered and analyzed by HPLC-MS/MS. Quantification was performed using matrix-matched calibration curves with external standard method.

Satisfactory linear relationships were obtained for target pesticides within the range of 1–100 μg/L, with correlation coefficients (r) all higher than 0.995. The spiked recoveries of 16 kinds of pesticides ranged from 77.2% to 114.7%, with relative standard deviations of 1.2%–9.4%. The limits of quantitation of the method were 0.16–3.46  μg/kg.

This method is simple, accurate and rapid. It can be applied to the detection of relevant pesticide residues in tea, and provides reliable technical support for quality-safety risk monitoring and pesticide residue control of tea agricultural products.

To investigate the pollution conditions of neonicotinoid pesticides in fruits and vegetables sold in Xingtai, and assess the dietary exposure risk of neonicotinoid pesticide residues to local residents.

A total of 210 vegetable and fruit samples were collected from markets in Xingtai from 2021 to 2024. The 12 kinds of neonicotinoid insecticides were determined by ultra performance liquid chromatography-tandem triple quadrupole mass spectrometry. The detection and over-limit situations of neonicotinoid pesticides were evaluated in accordance with GB 2763—2021 National food safety standard-Maximum residue limits for pesticides in food. Chronic and acute dietary exposure risk assessments of neonicotinoid pesticides were conducted by the point assessment method. Hazard evaluation of the detected pesticides was performed by the food safety index.

Among the 12 kinds of neonicotinoid insecticides monitored in this study, 8 were detected at varying levels, with detection rates ranging from 0.5% to 34.8% and exceedance rates from 1.0% to 6.7%. Moreover, multiple pesticides were detected in a single sample. Both the chronic and acute dietary intake risk values of the 12 kinds of neonicotinoid insecticides were below 100%, the food safety index of each individual pesticide was less than 1, and the overall food safety index was also below 1.

Certain neonicotinoid insecticides are detected and found exceeding standard limits in vegetables and fruits sold in Xingtai City. However, the dietary intake risks identified in this monitoring are all within acceptable ranges, indicating an overall good safety level.