Method for determining vitamins A, D and E in milk powder

Abstract

The invention relates to a method for determining vitamins A, D and E in milk powder. The method comprises the steps as follows: uniformly mixing a milk powder sample, weighing a proper quantity of the milk powder sample, adding water, absolute ethyl alcohol, ascorbic acid, BHT and KOH aqueous solutions, performing heating saponification, and performing cooling and diluting to a specified volume after saponification; determining the content of vitamins A, D and E in the solution by an HPLC (high performance liquid chromatograph) with a double-valve and three-pump system; determining whether vitamins A and E exist in the sample or not by comparing the retention time of the sample and a standard substance in one-dimensional liquid chromatography; determining whether vitamin D exists in the sample or not by comparing the retention time of the sample and the standard substance in two-dimensional liquid chromatography; calculating the content of vitamins A, D and E in the sample according to the amounts of vitamins A, D and E after conversion. The operation steps are simplified, the pretreatment time is greatly shortened, the labor and reagent costs are saved, automatic online purification detection is realized, the sensitivity is improved, and the accuracy and reproducibility of test results are guaranteed.

Description

[technical field] [0001] The invention belongs to the technical field of analytical chemistry, in particular to a method for determining vitamins A, D and E in milk powder. [Background technique] [0002] Vitamins widely exist in various organisms, and about dozens of types have been discovered so far, with different chemical structures, including aliphatic, aromatic, alicyclic, heterocyclic and steroidal compounds. In terms of physiological functions, they are neither the main raw materials for various tissues nor the source of energy in the body, but they are small molecular organic compounds that are essential to participate in the mediation of substance metabolism. Vitamins A, D, and E are all non-polar hydrophobic isoprene derivatives, soluble in lipids and fat solvents, but insoluble in water, and belong to fat-soluble vitamins. Excessive intake, unbalanced intake or lack of intake will cause corresponding symptoms, affecting the growth and development of the body and...

AI Technical Summary

Problems solved by technology

[0005] In 2013, Wang Anqun et al. reported a method for the determination of vitamin A, D3, and E in feed by high-performance liquid chromatography in the journal "Environmental Monitoring Management and Technology". The matrix is ​​complex, which seriously damages the chromatographic column. At the same time, the low VD content is easily interfered by the matrix and cannot be detected, so it is difficult to popularize

However, its pre-treatment must be avoided through saponification, wall-breaking extraction, organic solvent phase inversion, and concentration of these tedious processes

Although the two-dimensional column switching method solves the problem of matrix interference, due to the diffusion phenomenon of the target substance in the process of chromatographic distribution, it is easy to broaden the chromatographic peak and cannot be detected. Obviously, it is difficult to reduce the detection limit of VD, which cannot meet the test requirements of low-content samples

In 2015, Yangzhou Institute of Quality Inspection reported a method for testing vitamin A, D, and E in milk powder by high performance liquid chromatography tandem mass spectrometry. Although the sensitivity of the method has been improved, the pretreatment process still cannot avoid saponification extraction and organic solvent phase conversion concentration, etc. step

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