Method for rapidly detecting lead chromate in tea leaves

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...

AI Technical Summary

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 Method, microwave digestion method, pressure tank digestion method, the method involves concentrated strong acid, high temperature and high pressure, the digestion time is as long as 3-5 hours, the acid gas volatilization is serious, professional technicians are needed, and the detection is the total lead content, part of the source of lead Inside the tea; "Limits of Chromium, Cadmium, Mercury, Arsenic and Fluoride in Tea" (NY659-2003) stipulates that the limit of chromium in tea is 5.0mg / kg, and the "National Food Safety Standard for the Determination of Chromium in Food" ( GB 5009.123-2014) atomic absorption graphite furnace method for detection of chromium content, "Determination of art green (lead chrome green) in tea" (BJS 201910) issued by the State Administration for Market Regulation uses liquid chromatography and ion chromatography to determine CrO 4 2- The advantages of this type of method are high detection sensitivity and good stability, but the disadvantage is that large-scale detection equipment and supporting implementation are required. Concentrated strong acid, high temperature or high pressure are used in the sample pretreatment process, and the entire sample pretreatment process requires 3 Hours or more, the overall detection cost is high, measured as the total chromium content in the tea, part of the chromium comes from the inside of the tea

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