Objective To establish a method for the determination of 9 kinds of pesticide residues in black tea and green tea based on multi-walled carbon nanotubes (MWCNTs) combined with gas chromatography-tandem mass spectrometry (GC-MS/MS). Methods The key parameters were optimized by single factor experiment, including the amount of MWCNTs, ultrasonic extraction time and extraction solvent, and the methodological performance was evaluated, including linear range, detection limit, quantification limit, accuracy and precision. Results The linear relationship of this method was excellent, with correlation coefficients all greater than 0.99. The limits of detection and limits of quantitation were 0.002-0.004 mg/kg and 0.007-0.012 mg/kg, respectively. The recoveries of 9 kinds of pesticides in black tea and green tea were 71.52%-118.80%, and the relative standard deviation were 1.00%-6.92%. Conclusion This study successfully establishes a pesticide residue detection method based on MWCNTs combined with GC-MS/MS, which has the advantages of high sensitivity, high recovery rate and low solvent consumption, and significantly improves the detection efficiency. The actual sample detection shows that this method is suitable for the rapid screening of commercially available tea, and provides reliable technical support for the regulatory authorities.

Objective To assess the dietary exposure risk of mycotoxins for Beijing consumers, based on the mycotoxins contamination data during the cold storage period of Castanea mollissima which harvested in Huairou District, Beijing. Methods Castanea mollissima samples were collected from the 4 highest yielding townships in Huairou District. Samples were stored in a cold storage for 1 year and sampled once a month to determine the content of 21 kinds of fungal toxins. Based on the 2002 Beijing residents’ dietary consumption survey data, point estimation method, probability method and cumulative risk assessment modeling method of multiple fungal toxins were used to evaluate the acute and chronic dietary exposure risks of different genders of consumers. Results The estimated daily intake levels of alternariol and alternariol monomethyl ether in some Castanea mollissima samples were higher than 2.5 ng·kg^-1·bw·d^-1. The estimated daily intake levels of tentoxin and tenuzonic acid in all samples during the entire storage period did not exceed 1500 ng·kg^-1·bw·d^-1. The estimated daily intake/tolerable daily intak of nivalenol, fumonisin B₁, total fumonisin and zearalenone were all less than 100. The margin of exposure (MOE) was used to analyze the sterigmatocystin, and the result was greater than 10000. The 2 kinds of different chronic effects were analyzed for ochratoxin A. The cumulative risk assessment of mycotoxins in Castanea mollissima samples showed that some samples had MOE below 100 after storage for about 10 months. Conclusion All varieties of Castanea mollissima samples are no significant risk of mycotoxins to consumers after stored for 9 months in cold storage, and consumers can safely eat them. But multiple mycotoxins are detected simultaneously during the late stage of storage, which may pose health risks to humans. In order to clarify these health risks further, more toxicological data is needed.

Objective To establish and evaluate the application of direct mercury analysis for the determination of total mercury in food. Methods A direct mercury analysis method was developed based on catalytic pyrolysis-gold amalgamation atomic absorption spectroscopy. By stepwise optimization of pyrolysis temperatures (150 °C/550 °C for low-concentration ranges and 200 °C/650 °C for high-concentration ranges) and carrier gas flow rates (150-200 mL/min), plant-derived samples (e.g., rice, jujube), animal-derived samples (e.g., snakehead, fish meal), and 14 kinds of food samples were analyzed. The method’s detection limit, accuracy, stability and spike recovery were evaluated to assess its performance and matrix applicability. Results The method established dual linear calibration curves of 0-10 ng and 25-200 ng, with correlation coefficients of 0.9993 and 0.9998, respectively. The limit of detection and limit of quantitation were 0.0002 mg/kg and 0.0005 mg/kg, respectively. Spike recoveries ranged from 90% to 116%, the intra-day and inter-day repeatability relative standard deviation was less than or equal to 6.5% and less than or equal to 7.7%, respectively. The method was systematically validated for complex matrices, including plant-derived, animal-derived, and processed foods, with all results complying with the GB 2762-2022 National food safety standard-Limits of contaminants in foods. Conclusion The proposed method eliminates the need for chemical digestion in sample pretreatment, significantly shortens the analytical time, and prevents mercury volatilization losses. It overcomes the limitations of single-matrix analysis and achieves rapid total mercury detection in diverse complex food matrices, thereby providing an efficient and reliable technical solution for food safety risk monitoring and regulatory compliance.

Objective To establish a method for simultaneous determination of 23 kinds of per-and polyfluoroalkyl substances (PFASs) in food by high efficiency reinforced fat removal bilayer column-ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Methods The sample was extracted and centrifuged, high efficiency reinforced fat removal bilayer column method was adopted for the purification, the sample solution was separated on an Shim-pack GISS Hp 3 μm C₁₈ column using 2 mmol/L ammonium formate and methanol as mobile phase for gradient elution, detected by tandem mass spectrometry with multiple reactions monitoring (MRM), and quantified by internal standard method. Results The 23 kinds of target compounds of PFASs were well retained on the chromatographic column with good linearity in the range of 0.2-50.0 µg/L (r²>0.995). The limits of detection (LODs) and the limits of quantitation (LOQs) about perfluorobutanoic acid (PFBA) and perfluoropentanoic acid (PFPeA) were 0.06 μg/kg and 0.18 μg/kg respectively. LODs and LOQs about the remaining 21 kinds of perfluorinated compounds were 0.03 μg/kg and 0.09 μg/kg, respectively. The recoveries of the 23 kinds of target compounds of 2.0 μg/kg and 10.0 μg/kg spiked levels in the meat, fish and milk matrix ranged from 70.3%-120.0% with relative standard deviations of 1.56%-9.65%. Conclusion This method is easy, fast, accurate and sensitive, which is suitable for the determination of 23 kinds of PFASs in food.

Objective To compare the resistance differences of 18 kinds of bacterial strains and 2 kinds of biological indicators to chlorine-containing disinfectants, hydrogen peroxide and quaternary ammonium compounds. Methods Strains were selected from food, environment and human sources, including gram-negative bacteria, gram-positive bacteria and spore-forming bacteria (6 kinds of strains per category). Species identification was performed using matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) and biochemical assays. The 2 kinds of biological indicators, namely Staphylococcus aureus ATCC6538 and Escherichia coli 8099 were used as reference strains. Bacterial suspensions (2.0×10⁸-10.0×10⁸ CFU/mL) were prepared to test their tolerance to sodium hypochlorite (available chlorine 0.00400%-0.00499%), hydrogen peroxide (7.5%), and benzalkonium bromide (3.996 mg/mL). All bacterial strains were treated with disinfectants for 3 minutes. By calculating the killing log value (KL) of disinfectants against different bacterial strains, the differences in resistance of different species of bacterial strains to 3 kinds of disinfectants were compared. Results The bactericidal efficacy ranked as sodium hypochlorite, hydrogen peroxide, benzalkonium bromide. Different species showed significant variations in resistance to disinfectants. Among 3 categories of bacterial strains (gram-negative bacteria, gram-positive bacteria and spore-forming bacteria), there were strains within each category that exhibit higher resistance to disinfectants than 2 kinds of biological indicators. Conclusion Sodium hypochlorite and hydrogen peroxide exhibit superior bactericidal effects compared to benzalkonium bromide. The resistance to disinfectant of bacteria is species-specific and cannot be predicted solely by gram classification. The screening scope for biological indicators should be expanded based on actual needs.

Objective To establish a safety, rapid, cost-effective and reliable analytical method for trace elements detection in aluminum foil based on fiber laser induced breakdown spectroscopy. Methods Using standards to evaluate analytical sensitivity and limit of detection of fiber laser induced breakdown spectroscopy after optimization of laser pulse width, pulse energy, repetition rate and baseline-correction, and the optimized method was applied to analyze trace elements in aluminum foil samples. Results Calibration curves for most elements achieved regression coefficients up to 0.99. Detection sensitivity and limit of detection followed the descending order of Mn>Cr>Cu>Ti>Mg>Fe>Zn>Si, and the average relative error of leave-one-out cross validation of all the elements was 14.45%. The detection results of 8 kinds of trace elements in 27 kinds of aluminum foil samples showed that Fe and Si were frequently detected, while Cu and Ti elements were rarely detected and Cr, Mg, Mn and Zn elements were not detected. Conclusion This method requires no sample preparation, offers rapid analysis speed, and enables simultaneous multi-element detection with high sensitivity, which promisingly makes it a reliable approach for rapid determination of trace elements in aluminum foil.

Objective To study the changes of acid value, benzo [a] pyrene, 4 kinds of polycyclic aromatic hydrocarbons (PAH4) and 16 kinds of polycyclic aromatic hydrocarbons (PAH16) content in frying french fries soybean oil/peanut oil at different temperatures and times. Methods The acid value in oils was titrated by anhydrous ether:isopropanol (1:1, V:V) using phenolphthalein as an indicator. The polycyclic aromatic hydrocarbons in samples were saponified by KOH/ethanol, extracted with n-hexane and cleaned-up by solid-phase extraction column, detected by gas chromatography-mass spectrometer. Results With the increase of frying temperature and time, the acid value increased rapidly, and the changes in peanut oil were more sensitive. At the same temperature, both benzo [a] pyrene and PAH4 showed an irregular fluctuating growth with time, and the higher the temperature, the faster the increase. The content of PAH16 rapidly increased with time and temperature, and its changes were more sensitive than those of benzo [a] pyrene and PAH4. Under the same conditions, the increase of benzo [a] pyrene, PAH4 and PAH16 in peanut oil was less than that in soybean oil. Conclusion At the same conditions, PAH16 shows more significant changes compared to benzo [a] pyrene and PAH4, so the limits of PAH16 should be given more attention.

Objective To establish a method for simultaneous determination of 50 kinds of antibiotics in dried sea cucumbers by multifunctional purification column combined with ultra performance liquid chromatography-tandem mass spectrometry. Methods The sample was extracted with 50% acetonitrile aqueous solution. After purification by multifunctional purification column, 50 kinds of antibiotics were separated using Waters ACQUITY UPLC HSS T3 (100 mm×2.1 mm, 1.8 μm) column with acetonitrile and 0.1% formic acid aqueous solution (include 5mmol/L ammonium acetate) for gradient elution. The mass spectrum was performed by electrospray positive ion mode scanning and multi-reaction monitoring acquisition, and quantified by external standard method. Results The results showed that 50 kinds of antibiotics exhibited good linearity in the range of 0.1-100.0 ng/mL, and the correlation coefficients were all greater than 0.99. The limit of detection ofthe method was 0.1-2.0 µg/kg, the limit of quantitation was 0.5-5.0 μg/kg. Recovery tests were carried out at 3 levels (1 times, 2 times, 10 times of the limit of quantitation) in the blank matrix, the average recoveries of the limit of detection were in the range of 54.83%-120.01%, and all the relative standard deviations (n=6) were 0.08%-9.15%. Conclusion This method has the technical advantages of simple operation process, excellent detection sensitivity, reliable precision, and good reproducibility, it can be applied to rapid screening and qualitative and quantitative detection of multiple antibiotics in dried sea cucumbers.

Objective To analyze the pesticide residues in Vigna unguiculata (L.) Walp. from typical vegetable-growing areas and evaluate their dietary exposure risk. Methods The pesticide residues of 288 Vigna unguiculata (L.) Walp. samples from 3 typical growing areas were prepared by standard methods. Risk assessments were performed utilizing index of food safety and hazard risk coefficients. Results Totally 39 pesticides were detected in 288 Vigna unguiculata (L.) Walp. samples with detection rates ranged from 0.35% to 24.31%. Low-toxicity pesticides with high detection rate were difenoconazole, cyromazine, chlorfenapyr, pyraclostrobin, chlorantraniliprole and acetamiprid, successively. Multiple pesticide residues were detected in Vigna unguiculata (L.) Walp. samples, and the detection rate and over-standard rate of samples in production were higher than those in farmers’ market and wholesale market. The risk assessment results indicated that hazard risk coefficients values of fenthion, cyromazine and thiamethoxam were more than 2.5 wih high risk; hazard risk coefficients values of carbofuran, triazophos, cyhalothrin and acetamiprid were more than 1.5 and less than 2.5 with moderate risk; hazard risk coefficients values of other pesticides were less than 1.5 with low risk.Conclusion The residues of various pesticides and the use of pesticides beyond the prescribed range are quite common on Vigna unguiculata (L.) Walp.. However, the risk of pesticides detected in most cases is relatively low. The main high risk factors are fenthion, cyromazine and thiamethoxam in Vigna unguiculata (L.) Walp. of typical growing areas, which need to be focused on supervision and increased monitoring. Some pesticides on Vigna unguiculata (L.) Walp. can be naturally degraded during storage, transportation and sales. The risk situation of Vigna unguiculata (L.) Walp. in the circulation stage is lower than that in the production stage, and the risk in the consumption stage will be further reduced.

Objective To establish a method for rapid detection of nutritional components in raw milk by milk composition analyzer. Methods This study used commercial raw milk as the test sample, and based on Fourier transform infrared spectroscopy (FTIR), it constructed a rapid detection method for 9 parameters such moisture, protein, fat, lactose, ash, non-fat milk solids, total dry matter, relative density and freezing point in raw milk. The precision and accuracy of the rapid detection method were evaluated by comparing it with the national standard detection results. Results The determination results of the milk composition analyzer were as follows: Moisture 86.00%-89.09%, protein 2.52%-4.51%, fat 2.65%-5.39%, lactose 3.81%-5.40%, ash 0.56%-0.80%, and non-fat milk solids 6.94%-9.81%. F-test and T-test were performed on 9 parameters including fat, lactose and non-fat milk solids. The maximum F-value was 9.00, less than 9.55, indicating no significant difference in precision for the 9 parameters. The maximum T-value was 20.82, less than 22.327, confirming no significant difference in accuracy for the 9 parameters. Both the milk composition analyzer method and the national standard method could accurately determine milk nutritional indicators. The results showed that the precision and accuracy of the established rapid detection method had no significant differences from those of the national standard method. Conclusion The rapid detection method for nutrient components in raw milk constructed in this study can be used for high-throughput and low-cost rapid screening of nutrient components in raw milk. National standard methods should be used as the benchmark for high-precision scenarios, supervision and admission, while daily monitoring should primarily rely on rapid detection results from milk composition analyzers.