Pre-treatment method for simultaneously determining rare-earth elements and lead of tea leaves

Abstract

The invention discloses a pre-treatment method for simultaneously determining rare-earth elements and lead of tea leaves and belongs to the field of analysis chemistry. The pre-treatment method disclosed by the invention comprises the following steps: (1) pre-digesting; (2) digesting with nitric acid; (3) digesting with H2O2; (4) removing acid; and (5) making up to constant volume. Compared with a digestion method for rare-earth elements and lead of tea leaves, regulated by standards in China, the pre-treatment method has the advantages that a required digestion device is simple so that the pre-treatment method is easy to popularize; meanwhile, needed reagents are few and thus the influences on the detection of a reagent blank are reduced; and a digestion step is simple and is easy to control in actual operation. The uniform pre-treatment method is used for treating a tea leaf sample, so that the problems in a detection process of the rare-earth elements and lead of the tea leaf sample that a pre-treatment method is complicated and digestion methods are different are solved; and the pre-treatment steps are greatly simplified, the detection efficiency is improved, the detection cost is reduced and the pre-treatment method is worthy of popularization and promotion.

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...

AI Technical Summary

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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