Method for measuring delta 13C values of benzoic acid in milk in online manner

Abstract

The invention discloses a method for measuring delta 13C values of benzoic acid in milk in an online manner, particularly relates to methods for applying liquid chromatograms-stable isotope ratio mass spectra to measuring delta 13C values of benzoic acid in milk in an online manner, and belongs to the technical field of stable isotope analysis. The method includes steps of 1), selecting appropriate liquid chromatographic columns; 2), preparing acidic mobile phases; 3),adjusting liquid chromatograms-stable isotope ratio mass spectra until the liquid chromatograms-stable isotope ratio mass spectra are in work states; 4), adjusting the concentration of benzoic acid in samples; 5), automatically injecting the samples by the aid of an automatic sample injector and measuring measured delta 13C values of the benzoic acid; 6), correcting measurement systematic deviation of instruments by the aid of reference materials with known delta 13C values; 7), computing the delta 13C values of the benzoic acid according to the systematic deviation. The method has the advantages of simplicity in operation, convenience, low detection limit and stable results. Besides, dependence on manual sample injection operation can be prevented, and the delta 13C values can be continuously analyzed for 24 h.

Description

Technical field: [0001] The invention relates to on-line determination of the stable carbon isotope ratio of benzoic acid in milk (denoted as δ 13 The method of C) belongs to the technical field of stable isotope analysis. Background technique: [0002] "Food is the most important thing for the people, and food safety is the first." my country's food safety supervision has risen to a national strategy. The most stringent supervision, the most severe punishment, the most serious accountability, resolutely control the pollution on the table, and effectively guarantee the "safety on the tip of the tongue". Falsification, cutting corners, adding cheap raw materials and other behaviors to make huge profits, this kind of economic profit-driven adulteration will also bring food safety problems, but because the ingredients mixed with the existing ingredients of the food are the same, it brings technical problems to the detection. Challenges have also brought difficulties to supervisi...

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Problems solved by technology

[0006] However, the research and application of stable isotope technology in the food field has only a history of more than 40 years, and the research and application of this technology are still in development, while the carbon isotope analysis (δ 13 C value) reports are relatively few: people such as Scharschmidt (Variation of Transition-State Structure as a Function of the Nucleotide in Reactions Catalyzed by Dehydrogenases-Liver Alcohol Dehydrogenase with Benzyl Alcohol and Yeast Aldehyde Dehydrogenase with Benzaldehyde) extracted the yeast extract by liquid-liquid extraction Benzoic acid was converted to carbon dioxide under off-line vacuum conditions and analyzed by stable isotope ratio mass spectrometry, but this method requires a large sample of benzoic acid; Krummen et al. (A new concept for isotope ratio monitoring liquid chromatography / mass spectrometry) and Heuer et al. (Onlineδ 13 C analysis of volatile fatty acids insediment / pore water systems by liquid chromatography-isotope ratio massspectrometry) used micro-injection technology combined with liquid chromatography-stable isotope ratio mass spectrometry to determine the δ of benzoic acid 13 C value, however, this method is also only applicable to high-purity benzoic acid samples and cannot be automatically injected, and can only be analyzed by manual injection mode, which greatly increases the workload and undoubtedly reduces work efficiency, while at the same time , although this method uses a liquid chromatography-stable isotope ratio mass spectrometer, the instrument only acts as a carrier, and cannot analyze benzoic acid in the mixture; Shexia (Stable carbon isotopic compositions of organic acids into total suspended particles and dusts from Guangzhou, China) et al. used gas chromatography-combustion-stable isotope ratio mass spectrometry combined with derivatization degradation technology to determine the δ of aromatic organic acids 13 C values, but this technique can only analyze the δ averaged over all aromatic amino acids 13 C value, but cannot give the δ of benzoic acid 13 C value, in addition, the derivatization and degradation steps in the pretreatment process may also lead to isotope fractionation, making the determination results inaccurate

There is no report on the carbon isotope analysis of benzoic acid in milk