Objective: To establish a method for the determination of geniposide in Qinghuozhi cereal by ultraviolet spectrophotometry (UV), and to evaluate the uncertainty of the result.

Methods: UV method was used to verify the method and determine the content of geniposide. The uncertainty of the result was evaluated, the synthetic uncertainty was calculated, and the measurement result was given.

Results: The uncertainty evaluation showed that the extended uncertainty of the determination result was ±1.724% (k=2) under 95% confidence interval.

Conclusion: The established uncertainty evaluation method can provide a reference for the uncertainty analysis of the active components of traditional Chinese medicine compound preparations by ultraviolet spectrophotometry.

1. Experimental part

1.1 Instruments and reagents

SwitzerlandMETTLERTOLEDO UV-1500PC - Ultraviolet Visible Spectrophotometer (Shanghai Meixi Instrument Co., LTD.), AUW220D 1 in 100,000 electronic balance (JapanSHIMADZU), AB104-N 1 in 10,000 electronic balance (SwitzerlandMETTLERTOLEDO), BL6-189A Ultrasound instrument (ShanghaiBILON)

Gardeniside reference product (batch No. : 110749-201919, quality score: 97.1%), purchased from China National Institute of Food and Drug Control; Qinghuozhi cereal (commercially available, batch number: 210401, 210503, 210806); Methanol (analytical pure, Shanghai Zhenxing Chemical Plant), water for Milli-Q ultrapure water.

1.2 Methods and results

1.2.1 Preparation of reference solution

Accurately weigh the appropriate amount of dried gardeniside reference product, place it in a 10mL measuring bottle, add the appropriate amount of chromatograde methanol, shake to make the reference product fully dissolved, continue to add chromatograde methanol dilution to the scale, shake well, and obtain a reference product reserve solution with a mass concentration of 0.8124mg/mL. Precisely measure 1mL of the control product reserve solution and place it in a 25mL volumetric bottle, dilute it with solvent to the scale, and fully shake it, that is, prepare the control product solution.

1.2.2 Preparation of test product solution

Take 20 pieces of Qinghozhi cereal test product, remove coating, grinding, precision weighing powder about 0.15g, pour into 50mL measuring bottle, add about 40mL methanol solution, ultrasonic treatment for 30min, cool, then use methanol to scale, shake well, filter with microporous filter membrane, precision take continued filtrate 1mL placed in 25mL volumetric bottle, add methanol dilution to scale, That is, to prepare the test product solution.

1.2.3 Determination method

Take different concentrations of reference product solution and methanol solution, according to the UV determination method, at the wavelength of 238nm to determine the absorbance (A) of the above solutions, with A as the vertical coordinate, the concentration of each solution (C) as the horizontal coordinate, draw a standard curve. Take the prepared test product solution, according to the standard curve preparation under the determination method, determine the test product in the geniposide absorbance (A), according to the standard curve calculated the content of geniposide in the test product.

2. Uncertainty assessment

2.1 Mathematical model

According to the principle of UV determination, the formula for determining the content of geniposide in Qinghuzhi cereal is as follows:

In the formula, W is the content of geniposide in Qinghuozhi cereal; A is the absorbance of the sample solution; V1 is the dissolved volume of the test product; V2 is the diluted volume of the test product; E is the absorption coefficient of geniposide; l is the liquid layer thickness; m is the weight of the test product.

2.2 Content determination

Precision to take the appropriate amount of test product, according to method 2.1 as shown in the preparation of test product solution, with ultraviolet spectrophotometer respectively measured the absorbance value, according to the standard curve to calculate the Qinghuozhi cereal sample solution of geniposide content

Method Source: [1] WU Yougen, Chen Yanjun, LIU Juan. Uncertainty evaluation for determination of geniposide in Qinghuozhi cereals by ultraviolet spectrophotometry [J]. Brand and Standardization,2024,(05):26-28+33.

Instrument Parameters

UV-1500PC type - UV-Visible spectrophotometer

* Single chip microcomputer control, 128*64 bit liquid crystal display

* large liquid crystal display can display multiple sets of data
* huge memory space, can store multiple sets of data and curves
* automatic 0, adjust 100% function
* wavelength automatic adjustment
* light source automatic switching, Automatic switch of color filter
* Wide sample pool (5mm ~ 100mm)
* With a maximum of ten points standard sample construction standard curve measurement function
* Can directly input K, B factor to establish a standard curve for quantitative measurement
* Can directly input the standard sample and the corresponding concentration value to establish a standard curve for quantitative measurement
* Can be powered off to save the standard curve parameters of measurement Settings
* equipped with universal parallel printing connection Port, can print the title bar, measurement data, curve parameters, curve standard sample points and curves
* With USB interface
* Through PC software control to achieve more accurate and flexible measurement requirements such as spectrum scanning (standard)