A pretreatment method for simultaneous determination of rare earth elements and lead in tea

Abstract

The invention discloses a pretreatment method for simultaneously determining tea rare earth elements and lead, which belongs to the field of analytical chemistry. The pretreatment method of the invention includes (1) predigestion, (2) nitric acid digestion, (3) H2O2 digestion, (4) ) catch acid and (5) constant volume. Compared with the digestion method of tea rare earth elements and lead elements stipulated in the national standard, the digestion device required by the present invention is simple, easy to popularize, and requires less reagents at the same time, reducing the influence of reagent blanks on detection, and the digestion steps are simple. It is easy to control in actual operation. The present invention adopts a unified pretreatment method for tea samples, which well solves the problems of cumbersome pretreatment methods and different digestion methods in the detection process of rare earth elements and lead in tea samples, greatly simplifies the pretreatment steps, improves detection efficiency, and reduces The detection cost is worth popularizing and promoting.

Description

technical field [0001] The invention relates to the technical field of analytical chemistry, in particular to a pretreatment method for simultaneously determining tea rare earth elements and lead. Background technique [0002] Tea is the most vital and the most popular beverage among the three natural beverages in the world. With people's increasing requirements for food safety and quality, the quality and safety of tea has attracted more and more attention. In recent years, the problems of rare earth and lead in some teas have been exposed. In 2008, the European Union notified 12 batches of tea The lead in 7 batches of green tea exceeded the standard. In 2008, the Beijing Tea Quality Inspection Station received the test results of Anxi Tieguanyin products that major tea companies in Beijing voluntarily submitted for inspection. 70% of Tieguanyin products exceeded the national standard for rare earth elements. The limited value seriously affects the normal sales of tea and th...

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Problems solved by technology

[0004] The above pretreatment method, the dry ashing method uses high temperature burning to destroy the organic matter in the sample, and finally uses dilute nitric acid to dissolve the heavy metals in the ash, which generally takes 6 to 8 hours, which may cause the loss of volatile elements or the occlusion of the crucible, reducing the Measured value and recovery rate

The microwave digestion method is a kind of internal heating, the contact surface between the sample and the reagent is large, the closed system can avoid the loss of the elements to be measured, the digestion solution is clarified, and the acid is removed and then transferred to a constant volume. The test solution can be directly measured on the machine, but the operation steps are relatively complex Many, fewer samples digested at one time

The wet digestion method uses acid to destroy the organic matter in the sample under heating conditions. The temperature of the digestion process is low, and the elements to be measured are not easy to escape, but the amount of acid used is large, resulting in an increase in the blank value and a greater possibility of sample contamination by reagents.

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