Method for detecting lead content in tea-leaf

A technology of lead content and tea, which is applied in the field of qualitative or quantitative detection of heavy metal lead content in tea, which can solve problems such as difficulty in adapting, expensive detection instruments, and cumbersome detection steps

Inactive Publication Date: 2008-05-14
ZHEJIANG GONGSHANG UNIVERSITY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0006] The above methods for detecting heavy metals mostly use chemical instruments for detection, which are expensive, cumbersome detection steps, high detection cost, time-consuming, difficult t

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0055] Weigh 0.5000g of tea sample 1 to be tested in a conical flask, add 5ml of HNO 3 and 2ml H 2 o 2 , using a sealed pressurized microwave digestion tank with a household microwave oven, heating at low heat (119W) for 10 minutes, medium and low heat (231W) for 8 minutes, medium and low heat (231W) for 5 minutes, and high fire (385W) for 1 minute. Remaining acid is driven away with low heat, and digestive juice is obtained.

[0056] The isotopic mercury plating method and square wave stripping voltammetry were used to detect lead ions in the sample solution. Take the tea digestive juice with 0.1mol / L NH 4 Set the volume of Cl to 25 mL, put it in the electrolytic cell, add 100 μl of 0.1 mol / L mercury plating solution, adjust the pH value to 5.0 with concentrated ammonia water, fill with nitrogen to remove oxygen, and stir with a magnetic stirrer at a speed of 400 r / min. The screen-printed electrode was inserted into the electrolytic cell (the auxiliary electrode of the sc...

Embodiment 2

[0069] Weigh 0.5000g of the tea sample 2 to be tested in the Erlenmeyer flask, and the parameters of the digestion, detection method, data acquisition and processing system are the same as those in Example 1.

[0070] Apply a voltage to the working electrode, and detect the current value between the auxiliary electrode and the working electrode. Record the square wave stripping voltammetry peak height.

[0071] Add 100 μl of lead standard solution with a concentration of 10 μg / mL (ie: a=1.00 μg) into the electrolytic cell; apply voltage to the working electrode, and detect the current value between the auxiliary electrode and the working electrode; record the square wave dissolution after adding the standard solution Volt-ampere peak height.

[0072] The square wave stripping peak peak figure of lead as shown in Figure 1. Among them, curve 1-0.10mol / L blank NH 4 Cl bottom solution (pH value 5.0); Curve 2-the square-wave dissolution peak of lead in the sample to be tested; C...

Embodiment 3

[0080] Weigh 0.5000g of the tea sample 3 to be tested in the Erlenmeyer flask, and the parameters of the digestion, detection method, data acquisition and processing system are the same as those in Example 1.

[0081] Apply a voltage to the working electrode, and detect the current value between the auxiliary electrode and the working electrode. Record the square wave stripping voltammetry peak height.

[0082] Add 50 μl of lead standard solution with a concentration of 100 μg / mL into the electrolytic cell (ie: a=5.00 μg); apply voltage to the working electrode, and detect the current value between the auxiliary electrode and the working electrode; record the square wave dissolution after adding the standard solution Volt-ampere peak height.

[0083] Add 50 μl of lead standard solution with a concentration of 100 μg / mL into the electrolytic cell again (ie: a=5.00 μg); apply voltage to the working electrode, and detect the current value between the auxiliary electrode and the ...

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Abstract

The invention discloses a method for detecting of the heavy metal lead content of the teas, the major steps include that: the tea samples to be measured are carried out the microwave digestion in the presence of H2O2 and nitric acid with a certain proportion, 0.1mol/L of NH4Cl solution dilution digestion liquid is used, the mercury plating liquid is added till the concentration of mercury ions in the solution achieves 4 multiplied by 10 to <4>mol/L, and the solution is detected by combining a screen-printing electrode with a data collection and processing system. The invention applies the electrochemical analysis method, adopts the three-electrode-to-one screen-printing electrode, uses the method of mercury plating in situ and takes the square wave stripping voltammetry as the tection method, so the invention has the advantages of simple, rapid, sensitive, accurate and economic.

Description

technical field [0001] The invention belongs to the field of food safety detection, in particular to a method for qualitatively or quantitatively detecting the heavy metal lead content in tea. Background technique [0002] my country is a big exporter of tea, and tea is a dominant agricultural product traditionally exported by our country. Therefore, the hygienic status of tea has been paid much attention, and its heavy metal lead content is one of the most important hygienic detection indicators. [0003] As we all know, heavy metal lead is a highly accumulative, multi-affinity physiological and neurotoxic substance, which can cause toxicity to almost all important organs and systems of the human body, such as the central nervous system, immune system, reproductive system and endocrine system, etc. , wherein the poisoning of the central nervous system is particularly serious. For children, even trace amounts of lead pollution can damage their nervous system and affect the...

Claims

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Application Information

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IPC IPC(8): G01N27/48
Inventor 赵广英吴艳燕
Owner ZHEJIANG GONGSHANG UNIVERSITY
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