Neonicotinoids have raised significant concerns due to their widespread use in agricultural applications and potential adverse health effects. Human biomonitoring of urinary neonicotinoids and metabolites enables the assessment of population exposure patterns and evaluation of the health risks associated with neonicotinoid exposure. In this study, we demonstrated automated liquid-liquid extraction and ultra-high performance liquid chromatography tandem mass spectrometry for the determination of urinary neonicotinoids and their metabolites in human biomonitoring. The solvent for liquid-liquid extraction was optimized, and the analytical performance for determining urinary neonicotinoids and their metabolites was validated. The method was used for the determination of urinary neonicotinoids and their metabolites in the human biomonitoring of 225 healthy participants. The associations of urinary neonicotinoids and their metabolites with oxidative stress biomarkers were assessed by Bayesian Kernel Machine Regression analysis. The method showed excellent linearity for the determination of neonicotinoids and their metabolites in the range of 0.05 ng/mL to 30.0 ng/mL, with the inter-day and intra-day recoveries of 90-102 % and relatively standard deviations of 3.2-4.5 %, respectively. Males and females showed different urinary concentrations of neonicotinoids and their metabolites. Females displayed higher urinary concentrations of dinotefuran than males, while males had significantly higher urinary concentrations of acetamiprid and thiacloprid than females. There were significant positive associations of urinary concentrations of neonicotinoids and their metabolites with oxidative stress biomarkers. Thiacloprid was the most significant compound that contributed to elevated levels of oxidative stress biomarkers. The method exhibited high efficiency and reliable analytical performances for the determination of urinary neonicotinoids and their metabolites, showing great promise in large-scale sample analysis of human biomonitoring applications.

Bovine coronavirus (BCoV), bovine norovirus (BNoV), and bovine rotavirus C (BRVC) are common diarrheal viruses in cattle and pose significant threats to herds and humans. In this study, we collected 194 fresh fecal samples from adult cattle between September 2022 and January 2024 in Guangdong Province, China. We presented the genetic characteristics of 24 newly identified enteric virus strains in cattle, including two bovine coronavirus (BCoV) strains (GD-GZ-01 and GD-GZ-02), one bovine norovirus (BNoV) strain (BYN7), and 22 bovine rotavirus (BRV) strains (BRVB, BRVC, and BRVH, representing groups B, C, and H, respectively). Genetic analysis was conducted via MEGA-X, MAFFT, RDP, SimPlot and Rstudio software. The reference strains’ related genes were retrieved from GenBank for comparison and analysis via MegAlign and Snapgene. The detection rates for BCoV, BNoV, and BRVC were 8.76

Arsenic is a widely studied toxic element that exists in various species with different oxidation states and forms in the environment and biological systems. The different physicochemical properties, environmental behaviors, and toxicities of these arsenic species make speciation analysis essential for environmental monitoring and human health risk assessment. In this study, we demonstrated the determination and monitoring of six arsenic species, including arsenite (AsIII), arsenate (AsV), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenocholine (AsC), and arsenobetaine (AsB) in seafood using high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). We optimized the chromatographic condition and sample preparation for the separation and extraction of arsenic species, and the method was validated with accuracy and reproducibility using certified reference materials and actual samples. Baseline separation of the arsenic species was achieved within 12 min, and oven heat extraction was selected for sample preparation. The method showed excellent linearity for arsenic species from 0.1 to 100 μg L-1, with recoveries ranging from 92% to 123%, intra-day precision of 0.9-5.0%, and inter-day precision of 1.1-19.4%. The method was further used to determine the arsenic species in 109 mollusks, 195 crustaceans, and 195 marine fish samples from Guangdong, China. Distinctive patterns of arsenic species distribution were observed among different seafood categories. AsB was consistently the predominant species across all samples, with a detection frequency higher than 97.9% and contributed to more than 90% of total arsenic, other arsenic species showed marked variations in their occurrence and concentrations.

Objective: To develop a method for the simultaneous detection of four sulfonamide residues in prawns—sulfadiazine, sulfathiazole, sulfamerazine, and sulfamethazine—using ultrasound-assisted matrix solid-phase dispersion extraction combined with pre-column derivatization and high-performance liquid chromatography (HPLC). Methods: By optimizing extraction conditions, ethyl acetate was chosen as the extraction solvent and florisil as the solid dispersion agent. Sulfonamides were extracted from prawns using ultrasound-assisted matrix solid-phase dispersion, then derivatized with fluorescamine and analyzed by HPLC with fluorescence detection. Results: The sulfonamides exhibited excellent linearity within the concentration range of 2–100 μg/L, with correlation coefficients greater than 0.999. Detection limits were 0.5 μg/kg and quantification limits were 2 μg/kg. Spike recoveries for blank prawn samples ranged from 84.4% to 93.9% at 2 and 20 μg/kg, with relative standard deviations (n = 3) below 7.7%. Conclusion: The method is straightforward, efficient, and highly precise, meeting the standards for residue analysis.

Investigating pesticide exposure and oxidative stress in preschool children is essential for elucidating the determinants of environmental health in early life, with human biomonitoring of urinary pesticide metabolites serving as a critical strategy for achieving this objective. This study demonstrated biomonitoring of 2 phenoxyacetic acid herbicides, 2 organophosphorus pesticide metabolites, and 4 pyrethroid pesticide metabolites in 159 preschool children and evaluated their association with oxidative stress biomarker 8-hydroxydeoxyguanosine. An enzymatic deconjugation process was used to release urinary pesticide metabolites, which were then extracted and enriched by supported liquid extraction, and quantified by ultra-high performance liquid chromatography-tandem mass spectrometry with internal standard calibration. Dichloromethane: methyl tert-butyl ether (1:1, v/v) was optimized as the solvent for supported liquid extraction, and we validated the method for linear range, recovery, matrix effect and method detection limit. Method detection limit of the pesticide metabolites ranged from 0.01 μg/L to 0.04 μg/L, with satisfactory recoveries ranging from 70.5% to 95.5%. 2,4,5-Trichlorophenoxyacetic acid was not detected, whereas the other seven pesticide metabolites were detected with frequencies ranging from 10.1% to 100%. The concentration of urinary pesticide metabolites did not significantly differ between boys and girls, with the median concentrations being 9.39 μg/L for boys and 8.33 μg/L for girls, respectively. Spearman correlation analysis indicated that significant positive correlations among urinary metabolites. Bayesian kernel machine regression revealed a significant positive association between urinary pesticide metabolites and 8-hydroxydeoxyguanosine. Para-nitrophenol was the pesticide metabolite that contributed significantly to the elevated level of oxidative stress.

While polycyclic aromatic hydrocarbons (PAHs) are well-known for their potential carcinogenic and mutagenic effects, the health implications of exposure to oxygenated PAHs, with increased persistence and bioaccumulation, are less understood.

Previous studies have indicated adverse health effects of exposure to polycyclic aromatic hydrocarbons (PAHs), but evidence on the association between PAH exposure and immunity is scarce and its underlying mechanism is largely unknown. This study assessed human exposure to PAHs by determining the concentrations of PAHs in serum and their metabolites in paired urine. The oxidative stress and inflammation levels were evaluated by urinary DNA damage biomarker 8-hydroxydeoxyguanosine, white blood cell counts and C-reaction protein. We investigated the relationship between PAH exposure and seven immunological components, and explored the indirect roles of oxidative stress and inflammation by mediation and moderation analysis. Multivariate regression analysis revealed that 1-hydroxynaphthalene and 2-hydroxyfluorene were negatively associated with immunoglobulin A, and 3-hydroxyphenanthrene was negatively correlated with complement component 3. Restricted cubic spline analysis demonstrated nonlinear relationships between some individual PAHs or their metabolites with immunological components. Bayesian kernel machine regression and quantile g-computation revealed significant associations of higher PAH exposure with decreased immunoglobulin G and kappa light chain levels. Phenanthrene was the compound that contributed the most to reduced immunoglobulin G. Mediation analysis demonstrated significant indirect effects of 8-hydroxydeoxyguanosine and white blood cell counts on the association between higher PAH exposure and decreased immunological components. Moderation analysis revealed that PAH exposure and decreased immunological components are significantly associated with higher levels of C-reaction protein and white blood cell counts. The results demonstrated significant immunosuppression of PAH exposure and highlighted the indirect roles of oxidative stress and inflammation. Interventions to reduce systemic inflammation may mitigate the adverse immune effects of PAH exposure.

Polycyclic aromatic hydrocarbon (PAH) exposure has been associated with adverse health effects, and accu-mulating evidence suggests that PAH exposure may impair liver function. However, the underlying mechanisms linking PAH exposure and liver function impairment remain unclear. This study aimed to explore the association between PAH exposure and liver function biomarkers, and the mediating effects of inflammation and oxidative stress. The cross-sectional study included 155 adults and their urinary PAH metabolites (OH-PAHs) were determined, and eight liver function biomarkers were measured in paired serum samples. A comprehensive statistical analysis investigated the linear, non-linear, individual, and joint effects of the association between urinary OH-PAHs and liver function biomarkers. The results indicated significant positive associations between urinary OH-PAH concentrations and liver function biomarker levels, suggesting that PAH exposure may adversely affect liver function. 2-hydroxyfluorene was identified as the individual metabolite contributing significantly to elevated gamma-glutamyl transferase levels. Further stratification by gender revealed that this association is more pronounced in males. Moreover, we observed significant mediation effects of the oxidative stress biomarker 8-hydroxy-2 '-deoxyguanosine and the inflammatory biomarkers C-reactive protein and white blood cell count on this association. The physiological responses triggered by PAH exposure are mediated by inflammation, which serves as a link between oxidative stress, cellular injury, and elevated liver enzyme levels. The results demonstrated that increased inflammation and oxidative stress mediated the association between increased urinary OH-PAHs and elevated liver function biomarkers. The results contribute to a better under-standing of the potential mechanisms underlying PAH exposure's hepatotoxic effects.

Lead and its compounds can have cumulative harmful effects on the nervous, cardiovascular, and other systems, and especially affect the brain development of children. We collected 4918 samples from 15 food categories in 11 districts of Guangzhou, China, from 2017 to 2022, to investigate the extent of lead contamination in commercial foods and assess the health risk from dietary lead intake of the residents. Lead was measured in the samples using inductively coupled plasma mass spectrometry. Dietary exposure to lead was calculated based on the food consumption survey of Guangzhou residents in 2011, and the health risk of the population was evaluated using the margin of exposure (MOE) method. Lead was detected in 76.5% of the overall samples, with an average lead content of 29.4 mu g kg-1. The highest lead level was found in bivalves. The mean daily dietary lead intakes were as follows: 0.44, 0.34, 0.25, and 0.28 mu g kg-1 body weight (bw) day-1 for groups aged 3-6, 7-17, 18-59, and >= 60 years, respectively. Rice and rice products, leafy vegetables, and wheat flour and wheat products were identified as the primary sources of dietary lead exposure, accounting for 73.1%. The MOE values demonstrated the following tendency: younger age groups had lower MOEs, and 95% confidence ranges for the groups aged 3-6 and 7-17 began at 0.6 and 0.7, respectively, indicating the potential health risk of children, while those for other age groups were all above 1.0. Continued efforts are needed to reduce dietary lead exposure in Guangzhou.

The recent Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic highlights the significant threat coronaviruses (CoVs) pose to public health. With their extensive cross-continental movements, migratory birds have the potential to serve as reservoirs and vectors for CoVs. This study aimed to investigate the prevalence of CoVs in birds in densely populated areas of Guangdong Province, China. Of the 128 samples collected from birds, six tested positive for CoVs (4.7%, 95% CI: 1.7–9.9%), and three complete viral genomes were obtained through viral metagenomics and PCR. Phylogenetic analysis revealed that two CoVs (MD_XN18 and SG_DWY40) belonged to the Gammacoronavirus genus, while one (CP_XN11) belonged to the Deltacoronavirus genus. Homology analysis revealed that the MD_XN18 strain discovered in mallards shares 95.6–97.4% sequence similarity with chicken infectious bronchitis viruses (IBVs), providing direct evidence that migratory mallards can transmit avian IBVs. Recombination analysis suggested that two genomic regions of SG_DWY40 could originate from unknown sources through recombination, potentially leading to the expression of a novel viral protein, provisionally named NS3.5. These findings underscore the ongoing transmission and evolution of CoVs among birds in cities near Guangdong Province, emphasizing the need for continued monitoring and research.

Brucellosis, a zoonotic disease caused by brucella infection, presents metabolic profile changes in patients that have not been extensively explored. This study utilized an ultra-high performance liquid chromatography tandem mass spectrometry based targeted metabolomic approach to comprehensively investigated metabolic changes in Brucella patients. Serum samples of brucellosis 50 patients and 50 well-matched healthy controls were analyzed for 228 metabolites, revealing significant alterations in 83 metabolites in brucellosis patients. Notably, disruptions were observed in key metabolite pathways, such as amino acid metabolism, urea cycle, tricarboxylic acid cycle (TCA), and fatty acid metabolism. Patients diagnosed with Brucellosis exhibited distinct differences in the levels of aspartate, glutamate, β-alanine, and asparagine when compared to controls. Within the urea cycle, a significant downregulation of arginine was observed, whereas ornithine levels were considerably upregulated. In the TCA cycle, concentrations of 2-oxoglutarate, succinate, and malate were significantly elevated, while citrate levels demonstrated a notable decrease. Due to the interruption of the TCA cycle, glycolysis was accelerated to compensate for the resultant energy deficit in Brucella patients. Concurrently, there was a significant increase in the levels of short and medium-chain fatty acids, while long-chain fatty acids showed a marked decrease. The study systematically revealed significant metabolic alterations in Brucellosis patients and further explored the potential correlation between these changes and clinic symptoms, including fatigue, muscle soreness and prolonged fever. The results enhanced our understanding of Brucellosis, offering valuable insights potentially beneficial in formulating more effective treatment strategies and improving prognostic approaches.

AbstractBackgroundThe number of human rabies cases caused by pet dogs in Guangzhou has been decreasing after years of comprehensive interventions. Consequently, attacks by stray dogs become a major issue in rabies control.ObjectivesTo share our experience of successfully dealing with rabies to provide some inspiration for prevention and control in countries and regions affected by it.MethodsA multidisciplinary One Health response was initiated to control this outbreak. Rabies virus was detected by PCR in the brain tissue of the associated stray dog. The sequences were aligned with reference sequences downloaded from GenBank using ClustalX. The maximum likelihood method implemented in MEGA 5.0 software package was used in a phylogenetic analysis of the aligned sequences.ResultsTwelve patients with exposure to the stray dog were identified in the field investigation. Rabies vaccines and immunoglobulin were administered to all patients within 48 h. After 1 year of follow‐up, no exposed patients showed symptoms. Maximum likelihood analysis of the nucleotide sequences obtained from the PCR products indicated that the rabies virus in the dog was closely related to isolates from neighbouring provinces of Guangdong as well as those from surrounding countries of China.ConclusionsMultidisciplinary One Health intervention is effective not only in the control of rabies but also in rapid emergency responses to attacks by rabid stray dogs.

Thyroid volume was proposed as a factor for malignancy in evaluating thyroid nodules. Previous studies have demonstrated the endocrine disrupting effect of polycyclic aromatic hydrocarbons (PAHs), but studies on the association between internal exposure of PAHs and thyroid volume are still scarce. In this work, we evaluated the association of polycyclic aromatic hydrocarbon internal exposure and urinary iodine concentration with thyroid volume in 590 school-age children without thyroid disease in Guangzhou, China. Urinary hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs), urinary iodine concentrations, and thyroid volumes were measured. The mean concentrations of urinary iodine and ΣOH-PAHs were 271.1 μg/L and 3.27 μg/L, respectively, and the mean thyroid volume was 2.4 mL. The associations of urinary iodine and OH-PAH concentrations with thyroid volume were investigated by multivariable linear regression and the Bayesian kernel machine regression models. Urinary ΣOH-PAHs were observed to be significantly positively associated with thyroid volume in multivariable linear regression models. The increase in each unit in the log-transformed concentration of ΣOH-PAHs caused 3.88% change in thyroid volume. The Bayesian kernel machine regression model demonstrated a positive joint effect of increased urinary ΣOH-PAHs on thyroid volume. Moreover, urinary ΣOH-PAHs were statistically significant linked to urinary iodine, and iodine mediated the relationship between urinary OH-PAHs and thyroid volume with the mediated proportions of 15.2%

This review summarizes the progress in suppressor over the period from 1981 to 2022, with an emphasis on the last ten years. Although quite well investigated for decades, suppression techniques, along with their crucial roles in emerging analysis areas, have presented significantly scientific challenges. Apart from the intrinsic characters of vital components used, the design of system and the suppression mechanism are extremely important to improve the performance of suppressor for ion chromatography. Early packed-column suppressor must be regenerated off-line using an acid or base solution and had too large delay volume to possess sufficient suppression capacity. The trend is shifting toward the development of convenient, sustainable and high-performance suppressors in several ways: (i) the substantial improvement in the electrolytically or chemically regenerated suppression techniques; (ii) the miniaturization of conventional suppressors and the use of innovative designs to reduce the void volume and the overall band dispersion; and (iii) the application of ion reflux to suppressor for reducing the generation of waste. The topical review mainly focuses on the development and special applications of suppressors, spacing from the design and performance of suppressors, buffer generation, analyte enrichment and matrix isolation. Furthermore, the current challenges and future prospects regarding suppressors are discussed.

Exposure to multiple environmental pollutants is ubiquitous and inevitable, but studies investigating their exposure effects on oxidative stress or inflammation have mainly been restricted to single-pollutant models. This study investigated the association of co-exposure to polycyclic aromatic hydrocarbons and phthalates with oxidative stress and inflammation. Using a cross-sectional study in adults, we measured urinary concentrations of metabolites of polycyclic aromatic hydrocarbons (OH-PAHs) and phthalates (mPAEs), urinary oxidative stress biomarker 8-hydroxy-2'-deoxyguanosine, and 9 inflammatory biomarkers in paired blood samples. The associations of urinary OH-PAHs and mPAEs with oxidative stress and inflammation biomarkers were evaluated by different statistical models. The Bayesian kernel machine regression and quantile g-computation was used to examine the joint effects, and increased levels of urinary concentrations of OH-PAHs and mPAEs were associated with elevated 8-hydroxy-2'-deoxyguanosine level and white blood cell counts. Exposure to polycyclic aromatic hydrocarbons contributed more significantly to inflammation, while exposure to phthalates contributed more to oxidative stress. Monoisobutyl phthalate was identified as the most significant metabolite contributing to elevated oxidative stress levels. 1-Hydroxypyrene was negatively associated with platelet, and monomethyl phthalate was significantly positively associated with interleukin 6 in multivariate linear regression. The restricted cubic spline analysis revealed non-linear patterns of 3-hydroxyfluorene with white blood cell, lymphocyte, neutrophil, and C-reactive protein. The results indicated significant associations between increased co-exposure to polycyclic aromatic hydrocarbons and phthalates with elevated oxidative stress and inflammation. Further investigation is needed to elucidate the underlying biological mechanisms and to determine the potential public health implications.

Polycyclic aromatic hydrocarbons (PAHs) are a class of highly lipophilic and ubiquitous, persistent organic pollutants with carcinogenic and mutagenic toxicities. They are a great public health concern, and avoiding exposure to them is a high priority. Human biomonitoring is critical for the evaluation of exposure levels to PAHs by the general population. In this work, we demonstrated the biomonitoring of eleven hydroxylated PAHs (OHPAHs) in urine samples from 226 volunteers from Guangzhou, and evaluated the health risks. The urinary PAH metabolites were released by enzymatic deconjugation, separated, and enriched by supported liquid extraction, and then quantified by ultra-high performance liquid chromatography-tandem mass spectrometry. The limit of quantification of the individual OHPAHs ranged from 10 ng/L to 40 ng/L, and satisfactory recoveries were obtained, ranging from 92.6% to 97.6%. The detection frequencies of the OHPAHs were 100%, and naphthalene metabolites were found at the highest concentrations with a geometric mean of 8.61 μg/L. The mean total OHPAH level in the urine samples of males (13.2 μg/L) was significantly higher than that of females (5.84 μg/L). Pearson correlation analyses indicated significant and positive correlations among urinary OHPAHs. The total estimated daily intake of PAHs was calculated, and a low health risk was obtained by evaluating their hazard quotients and hazard indexes.

目的 了解两广地区同季度米粉制品中脱氢乙酸含量,并初步评价其暴露水平.方法 2022年采集两广地区的230批次米粉制品,应用建立的米粉制品中脱氢乙酸含量的高效液相色谱方法测定其中脱氢乙酸含量,并初步进行人群暴露量评估.结果 2022年一至四季度湿米粉中脱氢乙酸含量分别为0.216、0.261、0.424和0.361 g/kg,平均含量为0.322 g/kg;不同季度干米粉中脱氢乙酸含量差异不大,其均值为0.016 g/kg;湿米粉中脱氢乙酸含量明显高于干米粉,干米粉、湿米粉和米粉干制品中脱氢乙酸检出率分别为38.8％、54.0％和44.3％.两广居民从米粉制品中摄入的脱氢乙酸日暴露量为20.5 mg/d.结论 两广地区干米粉的脱氢乙酸含量均较低,湿米粉中的脱氢乙酸含量明显高于干米粉.

Cadmium is an environmental pollutant that has extensive deleterious effects. However, the mechanisms underlying the hepatotoxicity induced by long-term exposure to cadmium remained undefined. In the present study, we explored the role of m6A methylation in the development of cadmium-induced liver disease. We showed a dynamic change of RNA methylation in liver tissue from mice administrated with cadmium chloride (CdCl2) for 3, 6 and 9 months, respectively. Particularly, the METTL3 expression was declined in a time-dependent manner, associated with the degree of liver injury, indicating the involvement of METTL3 in hepatotoxicity induced by CdCl2. Moreover, we established a mouse model with liver-specific over-expression of Mettl3 and administrated these mice with CdCl2 for 6 months. Notably, METTL3 highly expressed in hepatocytes attenuated CdCl2-induced steatosis and liver fibrosis in mice. In vitro assay also showed METTL3 overexpression ameliorated the CdCl2-induced cytotoxicity and activation of primary hepatic stellate cells. Furthermore, transcriptome analysis identified 268 differentially expressed genes both in mice liver tissue treated with CdCl2 for 3 months and 9 months. Among them, 115 genes were predicted to be regulated by METTL3 determined by m6A2Target database. Further analysis revealed the perturbation of metabolic pathway, glycerophospholipid metabolism, ErbB signaling pathway, Hippo signaling pathway, and choline metabolism in cancer, and circadian rhythm, led to hepatotoxicity induced by CdCl2. Collectively, our findings reveal new insight into the crucial role of epigenetic modifications in hepatic diseases caused by long-term exposure to cadmium.

Abstract Background Campylobacter spp., as a zoonotic pathogen, has been one of the most common pathogens that causes human gastroenteritis in developing countries. The objective of this study was to determine the antibiotic resistance of Campylobacter in children. Methods Stool samples were collected from pediatric patients under 14 years of age who visited hospital for acute diarrhea between February 2018 and January 2019. Campylobacter was isolated from samples using selective enrichment and culture and confirmed by PCR, genotypes were characterized by multilocus sequencing, and antibiotic resistance was determined by susceptibility and resistance genes to antimicrobials of medical importance. Results The overall prevalence of Campylobacter in children with diarrhea was 4.4% (53/1197). Higher prevalence was observed in children under five-year-old and in spring and autumn. Approximately 80% (42/53) of confirmed isolates were C. jejuni and ~ 20% (11/53) isolates were C. coli. Among the 51 isolates successfully typed, 43 sequence types belonging to 13 clonal complexes were identified, of which 44.2% (19/43) sequence types were novel. The majority of the Campylobacter isolates (74%) exhibited multidrug resistance and the most common antimicrobials resistant to were ciprofloxacin, tetracycline and nalidixic acid. All isolates (53/53) were positive of the tet(O) gene that confers resistance to tetracycline and the gyrA gene that confers resistance to quinolones/fluoroquinolones, 81% (43/53) isolates were positive of the ermB gene that confers resistance to macrolides, and 19% (10/53) isolates were positive of the aadE-sat4-aphA gene that confers resistance to aminoglycosides, respectively. Conclusions Despite the low prevalence of Campylobacter in children in the subtropical Guangzhou metropolitan, the high multidrug resistance of diverse MLST of Campylobacter indicated the importance of preventive strategies including routine surveillance in order to minimize the infections of antibiotic resistant Campylobacter in children.

目的:用全自动凯氏定氮仪测定蛋白质(以N计)不确定度进行分析与探讨.方法:采用GB 5009.5-2016第一法凯氏定氮法测定蛋白质(以N计)含量,建立数学模型,通过对各个不确定度分量的计算合成,找出影响测量不确定度的因素,最终得出样品中蛋白质(以N计)含量的扩展不确定度与合成标准不确定度.结果:蛋白质(以N计)含量测定的扩展不确定度为(20.93±0.25)％,k=2.结论:采用JJF 1059.1-2012《测量不确定度评定与表示》,对不确定度进行评定,确保蛋白质(以N计)含量结果的准确性.