Method for rapidly detecting lead chromate in tea leaves

A lead chromate and tea technology, which is applied in the field of rapid detection of lead chromate in tea, can solve the problems of nervous system liver, kidney damage, excessive lead and chromium content in tea soup, serious acid gas volatilization, etc., and achieves low price and excellent performance. , the effect of short processing time

Inactive Publication Date: 2019-12-17
WUHAN ACADEMY OF AGRI SCI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, the lead and chromium content of tea leaves artificially added with lead chromate can exceed the standard by 4-60 times of the national limit, even if lead chromate is not easily soluble in water (the solubility is 5.8×10 -8 g/mL), but because the water temperature for making tea is mostly above 80°C, which increases its dissolving capacity, it will still cause the lead and chromium content of the tea soup to exceed the standard, which is easily absorbed by the human body and accumulates in the body, which is harmful to the human nervous system, liver, kidney, etc. cause serious harm
It can be seen that, apart from the excessive lead and chromium content caused by the pollution of the growing environment and improper processing in the commercially available tea, the biggest impact on tea drinkers is the "refurbished tea" with illegally added lead chromate.
[0003] "National Food Safety Standard Limits of Contaminants in Food" (GB 2762-2017) stipulates the limit of lead in tea, including 5.0mg/kg in tea, 5.0mg/kg in dried chrysanthemum, and 2.0mg/kg in Kudingcha. "National Food Safety Standard for the Determination of Lead in Food" (GB 5009.12-2017) uses atomic absorption spectrometry, inductively coupled plasma mass spectrometry, and ultraviolet spectrophotometry to detect lead content, and the extraction method of lead in samples includes wet digestion M

Method used

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  • Method for rapidly detecting lead chromate in tea leaves
  • Method for rapidly detecting lead chromate in tea leaves
  • Method for rapidly detecting lead chromate in tea leaves

Examples

Experimental program
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Effect test

Embodiment 1

[0030] (1) Extraction of lead chromate in tea: Weigh 0.5g of a complete tea sample (accurate to 0.001g), place it in a 50mL plastic centrifuge tube, and add 25mL 1.0mol / L HNO 3 The solution was shaken and extracted at room temperature for 5 minutes, and the supernatant was taken out as the test solution;

[0031] (2) Standard curve drawing:

[0032] With 1.0mol / L HNO 3 The solution gradually dilutes the national standard material lead and chromium single element standard solution, prepares a series of standard curve solutions, and uses a portable heavy metal analyzer to detect the content of lead and chromium ions. The specific detection methods are:

[0033] Pb 2+ Ion content measurement: use a portable electrochemical heavy metal detector to detect, insert the disposable screen-printed electrode into the electrode mounting plug, and add 800μL of 0.1mol / L acetic acid-sodium acetate buffer solution and 40μL of 1.0ppm mercury modification solution into the analysis cell , Immerse the ...

Embodiment 2

[0055] (1) Extraction of lead chromate in tea: Weigh 0.5g of a complete tea sample (accurate to 0.001g), place it in a 50mL plastic centrifuge tube, add 12.5mL 1.0mol / L NaOH solution, shake and extract at room temperature for 5min, take it out Supernatant 5mL, add 5mL 2.0mol / L HNO to the removed supernatant 3 After acidification and cooling, it becomes the test liquid.

[0056] Steps (2), (3) (4) are the same as the first embodiment. The sample is also consistent with Example 1, and the test results are shown in Table 6.

[0057] Table 6. Test results of lead chromate content in tea samples

[0058]

[0059] The recovery rate of the alkaline extraction test result is 90%-105% compared with the acid extraction test result, which can be used for the extraction of lead chromate in tea.

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Abstract

The invention relates to the technical field of detection of heavy metals in food, and particularly discloses a method for rapidly detecting lead chromate in tea leaves. The method comprises the following steps: an extracting solution is added to react with lead chromate solids on the surfaces of tea leaves so that lead chromate is converted into detectable lead ions and chromium ions; and the contents of lead ions and chromium ions in the extracting solution are detected by using a portable heavy metal analyzer, and the content of lead chromate is calculated according to the contents of leadions and chromium ions. The method is simple to operate and safe, does not involve strong acid, strong alkali, high temperature and high pressure, has short pretreatment time and is suitable for quickly screening a large number of samples on site.

Description

Technical field [0001] The invention relates to the technical field of food heavy metal detection, in particular to a method for rapidly detecting lead chromate in tea. Background technique [0002] The new tea has a fresh and rich aroma, the color of the soup is clear and bright, and the taste is fresh and refreshing. The content of the effective components of the tea that people need in the old tea that has been stored for a long time is relatively reduced, the color is brown, the color of the soup is muddy, the aroma is reduced, the taste is worse, and the final tea is produced Chen Qi, stale taste and stale color, various advantages also make the price of new tea much more expensive than that of stale tea. This allows some unscrupulous traders to see the opportunity to make money, and refurbished tea came into being. The refurbished tea is mainly made by adding a substance-art green to the old tea. The main components of this substance are lead chromate and iron blue. In 2008...

Claims

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Application Information

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IPC IPC(8): G01N27/26G01N27/30G01N1/28G01N1/38
CPCG01N1/28G01N1/38G01N27/26G01N27/30
Inventor 姚琪战艺芳曾令文丁西夏定孙晓亮肖康飞
Owner WUHAN ACADEMY OF AGRI SCI
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