Determination methods and general steps of Chinese medicine content (2)

(3) Refining the test solution

After extracting Chinese medicinal powders or Chinese medicinal preparations, the result is often a mixture containing more impurities and pigments, which need to be purified and separated before analysis and determination

1.

Certain components of traditional Chinese medicine can be dissolved in acid or alkali, and the pH of the solution is adjusted by adding acid or alkali, so that it becomes insoluble and is precipitated

The solvent partition method can be used to separate some components in the mixture with different partition coefficients in the two-phase solvent

2.

In order to obtain accurate analysis results, the following conditions are required for the precipitation form and weighing form:

(1) Requirements for the form of precipitation: ①The solubility of precipitation must be small

(2) Requirements for the form of symmetrical weight: ①The form of weighing should have a certain chemical composition, so that the analysis result can be calculated according to the chemical formula

(3) Weighing form and result calculation: In the precipitation method, the analysis result is often calculated as a percentage

Calculation:

In many cases, the quantitative chemical composition of the measured component is inconsistent with the expression of the predicted component, and the amount in the form of weighing needs to be converted into the amount of the predicted component

Calculation:

W _b =W _c F.

In the formula, F is the conversion factor or chemical factor; W _b is the amount of the measured component; W _c is the amount in the form of weighing

(4) Precipitation method

1) Lead salt precipitation method: commonly used lead acetate or basic lead acetate reacts with the components or impurities to be tested to produce lead salt precipitation that is insoluble in water or dilute ethanol for purification and separation

2) Reagent precipitation method: add some alkaloid precipitation reagents to the water of alkaloids to form insoluble double salts, which can be precipitated out: such as betaine plus raven's ammonium salt; hesperidin, rutin, baicalin, etc.

3) Salting-out method: adding inorganic salts to the water extract of traditional Chinese medicine to a certain concentration, or reaching a saturated state, so that the solubility of certain components in the water is reduced to facilitate separation

3.

(4) Determination

Various measurement methods have big differences in sensitivity, selectivity and scope of application
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Therefore, an appropriate analysis method should be selected for determination according to the nature and content of the component to be tested and the requirements for the accuracy of the analysis result
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There are many quantitative analysis methods, and many of them can be used for the analysis of traditional Chinese medicine
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Commonly used quantitative methods include colorimetry, thin layer chromatography, gas chromatography and high performance liquid chromatography
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(5) Calculation and evaluation of analysis results

Calculate the content of the relevant components in the sample according to the measurement relationship of the relevant reactions in the analysis process and the data obtained from the analysis and measurement
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Use statistical methods to evaluate the measurement results and their error distribution
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Please refer to the relevant chapters for specific calculation formulas
.