Food additive turmeric detection

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A. General regulations

The reagents and water used in this standard, unless otherwise specified, refer to analytical pure reagents and Grade III water specified in GB/T6682. The standard titration solution, impurity determination standard solution, formulation, and product used in the experiment shall be prepared in accordance with the provisions of GB/T601, GB/T602, and GB/T603 unless other requirements are specified. The solution used in the experiment refers to aqueous solution when no specific solvent is specified for preparation

A.2 Identification Test

A.2.1 Color Reaction

Weigh a sample with a mass equivalent to 0.1g and a color value of 150, dissolve it in 200mL of ethanol, and the solution should show yellow, slightly green fluorescence. Weigh a sample with a mass equivalent to 1g and a color value of 150, dissolve it in 100mL of ethanol, add hydrochloric acid until the solution turns light orange, and this solution is the sample solution. Add boric acid to the sample solution, and the solution should appear red orange

A.2.2 Maximum Absorption Wavelength

Take the sample solution from A.3.3 Color Value Determination and detect it with a spectrophotometer. There should be a maximum absorption peak between the wavelengths of 420nm and 430nm.

A.2.3 Thin layer chromatography

A.2.3.1 Preparation of silica gel thin layer plate

Weigh 10g of silica gel, add 20mL of water, grind it into a slurry with suitable thickness in a mortar, and evenly apply it on the glass plate. The coating thickness is about 0.5mm, and it is activated at 100 ℃ for 30min

A.2.3.2 Developing agent

Ethanol: 3-methyl-1-butanol · Water: ammonia=4:4:2:1

A.2.3.3 Preparation of Sample Solution

Weigh a sample with a mass equivalent to 1g and a color value of 150, dissolve it in 100mL of ethanol, centrifuge at about 3000r/min for 10 minutes, and take the supernatant as the sample solution

A.2.3.4 Sampling

On a silica gel thin layer plate, use a micro syringe to draw 5uL of sample solution for sampling.

A.2.3.5 Unfolding and Observation

Place the sampled thin plate into a chromatography cylinder that has been saturated with the developing agent in advance, and unfold according to the upward method. When the solvent front exceeds 10cm, remove it and air dry it.

. There should be at least two yellow spots observed, and the Rf value should be between 0.40 and 0.85. All spots should show yellow fluorescence under ultraviolet light (approximately 366mm)

A.3 Determination of Color Value (425 ± 5) nm

A.3.1 Instruments and Equipment

Spectrophotometer

A.3.2 Reagents and Solutions

95% ethanol

A.3.3 Analysis Steps

Weigh 0.1g to 0.3g of powder sample to the nearest 0.0002g, or weigh 1g of extract or liquid sample to the nearest 0.0002g, dissolve with 95% ethanol, transfer to a 100mL volumetric flask, add 95% ethanol to the mark, shake well, then take 10mL and transfer to a 100mL volumetric flask, add 95% ethanol to the mark, shake well. If the solution is turbid, filter with filter paper to obtain the sample solution. Take this sample solution and place it in a 1cm colorimetric dish, using 95% ethanol as the blank control. Measure the absorbance using a spectrophotometer at the maximum absorption wavelength between 420nm and 430nm (the absorbance should be controlled between 0.2 and 0.8, otherwise the sample solution concentration should be adjusted and the absorbance should be re measured)

A.3.4 Result Calculation

Color valence (425 ± 5) nm, calculated according to equation (A.1):

 

In the formula:

A - the measured absorbance of the sample solution

C - concentration of the tested sample solution, in grams per milliliter (g/mL)

100- Concentration conversion coefficient

The experimental results shall be based on the arithmetic mean of the parallel measurement results. The absolute difference between two independent measurement results obtained under repeatability conditions shall not exceed 5% of the arithmetic mean

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