Simultaneous Determination of Amphenicols in Animal-Derived Foods by Solvent and Solid Phase Extraction With Ultrahigh-Performance Liquid Chromatography Tandem Mass Spectrometry.

BACKGROUND: The consumption of foods containing amphenicols, a type of antibiotic, is a major concern for human health. A stable and accurate detection method can provide technical support for food-safety monitoring. OBJECTIVE: An effective and efficient method was established for determining amphenicols in animal-derived foods through the simultaneous use of solid-phase extraction (SPE) cleanup and ultrahigh-performance liquid chromatography/mass spectrometry (UPLC-MS/MS). METHOD: Samples were extracted using 1.0% ammoniated ethyl acetate solution, degreased with n-hexane, and then concentrated and cleaned using a C18 SPE column. Next, gradient elution was performed using methanol and 0.05% aqueous ammonia as the mobile phase, followed by separation using a C18 column. The target compound was detected using electrospray ionization, both in positive and negative modes, through multiple reaction monitoring, and quantified using an internal-standard method. RESULTS: The content of chloramphenicol (CAP), florfenicol (FF), and florfenicol amine (FFA) (content range: 0.2-8.0 µg/kg) as well as that of thiamphenicol (TAP; content range: 1.0-40.0 µg/kg) show a good linear relationship, with a correlation coefficient of r > 0.999. Furthermore, recoveries of 86.7-111.9% and relative standard deviations of <9.0% were achieved. The limits of detection and quantification are obtained as 0.03-0.33 and 0.1-1.0 µg/kg, respectively. CONCLUSIONS: The proposed method has excellent stability and accuracy, and can be successfully used for the qualitative and quantitative determination of amphenicols, i.e., CAP, TAP, FF, and FFA residues in 210 animal-derived food samples, of which FF and FFA were detected in four samples. HIGHLIGHTS: A stable and accurate method was successfully established for the simultaneous determination of CAP, TAP, FF, and FFA in animal-derived foods using UPLC-MS/MS. Effective sample pretreatment was established, lipids were removed using n-hexane, concentration and cleanup were achieved with the C18 SPE column, and matrix effects were effectively reduced, thus improving the method's accuracy and stability. The method was validated for eight common animal-source foods, including beef, lamb, pork, chicken, egg, milk, fish, and honey. This method has good applicability for CAP, TAP, FF, and FFA in animal-derived foods.

[Fatty acid composition analysis and nutrition evaluation of milk and dairy products sold in Yinchuan City].

OBJECTIVE: To analyze fatty acid composition of milk and dairy products sold in Yinchuan City, and to evaluate their nutritional value. METHODS: Twenty-two types of milk and dairy products were collected in 2022-2023, including 14 types produced in Ningxia and 8 types not produced in Ningxia. Fatty acids were determined and analyzed according to the first method of National Standard for Food Safety Determination of fatty acids in Food(GB 5009.168-2016). The fatty acid polyunsaturated index(PI), atherogenic index(AI) and thrombosis index(TI) were used to evaluate the nutritional value of milk and dairy products. RESULTS: There were 25 kinds of fatty acids in milk and dairy products produced in Ningxia, which were more than those not produced in Ningxia. The main saturated fatty acids(SFA)were palmitic acid(30.14%-42.57%), the main monounsaturated fatty acids(MUFA)were oleic acid(15.45%-25.21%), the main polyunsaturated fatty acids(PUFA)were linoleic acid(1.79%-9.37%), the content of α-linolenic acid was 0.04%-0.95%, n-3 PUFA was 0.14%-0.95%. Oleic acid of adult milk powder, sheep milk powder, pure milk and Ningxia wolfberry milk were higher than others, linoleic acid of adult milk powder and walnut milk were higher than others. The value of oleic acid and linoleic acid of Ningxia pure milk was higher than that in imported pure milk, and the value of n-6 PUFA/n-3 PUFA was much lower than that in imported pure milk. The content of oleic acid and linoleic acid in Ningxia wolfberry milk was close to that of pure milk, higher than that of children's milk, and the total fat content was lower than that of children's milk. The n-6 PUFA/n-3 PUFA ratio of concentrated milk, walnut milk, sweet milk, pure milk, Ningxia wolfberry milk, adult milk powder 1, sheep milk powder was close to the ideal intake value of dietary fatty acids recommended by the Chinese Nutrition Society. Except for low-fat pure milk, ice cream yogurt, imported pure milk, children's milk 1, adult milk powder 1 and sheep milk powder, the n-6 PUFA/n-3 PUFA ratio of other milk and dairy products in Ningxia were close to the recommended value of the Food and Agriculture Organization of the United Nations and World Health Organization. SFA∶MUFA∶PUFA was(1.99-4.23) ∶1∶(0.08-0.38), PI range: 1.87-11.27, AI range: 1.67-4.32, TI range: 2.34-5.76. CONCLUSION: The fatty acid composition of 22 types of milk and dairy products in Yinchuan City was different, and the nutrition was slightly different.

[Investigation and health risk assessment of veterinary drug residues in chickens and eggs sold in Ningxia from 2016 to 2020].

OBJECTIVE: To understand the monitoring status of veterinary drug residues in chickens and eggs sold in Ningxia from 2016 to 2020, and to evaluate the health risks of human intake. METHODS: A total of 303 chicken and 237 eggs were collected from 2016 to 2020, and the veterinary drug residues in chickens and eggs sold in Ningxia were detected and analyzed by high performance liquid chromatography-tandem mass spectrometry. The food safety index method was used to assess the health risks in combination with the dietary intake of residents. RESULTS: The detection rate of veterinary drug residues in chicken was 38.0%(115/303), and the over-standard rate was 7.6%(23/303). The detection rate of veterinary drug residues in eggs was 26.6%(63/237), and the over-standard rate was 19.8%(47/237). The food safety index of doxycycline in chicken was 4.59, and the food safety indexes of doxycycline, flumequine and flufenicol in eggs were 7.09, 26.5 and 2.33, respectively, all of which were much higher than 1, suggesting that there were health risks. The food safety indexes of other substances were all less than 1, and the food safety indexes were all acceptable. CONCLUSION: Veterinary drugs were widely detected in chicken and eggs in Ningxia from 2016 to 2020. Some veterinary drugs had hidden health risks.

[Study on the application and evaluation of methods for gene and antigen detection in plague surveillance program].

OBJECTIVE: To apply and evaluate new methods regarding specific gene and antigen detection in plague surveillance program. METHODS: 1798 samples from natural foci of plague were tested, using internal quality control multiple-polymerase chain reaction, F1 antigen marked by immuno chromatographic assay and enzyme linked immunosorbent assay. Culture of Yersinia pestis and reverse indirect hemagglutination assay were used as reference diagnostic methods. RESULTS: The overall positive rate of culture on Yersinia pestis together with gene and antigen detection was 7.34%, showing an 16.81% increase when comparing to 6.28% using Yersinia pestis culture method alone. The rate of coincidence was 97.13%. CONCLUSION: The new standard being used for specific gene and antigen detection could increase the positive rate of diagnosis on plague.