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    Home > Coatings News > Paints and Coatings Market > The method of measuring the total lead content in toy paint is discussed

    The method of measuring the total lead content in toy paint is discussed

    • Last Update: 2020-12-05
    • Source: Internet
    • Author: User
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    0 Introduction
    lead is currently recognized as one of the toxins affecting the development of the central nervous system in the human body, children's gastrointestinal absorption of lead is about 5 times higher than that of adults. Now many toys are coated with paint to make it beautiful, and children like to lick and bite toys, toy paint lead content is an important indicator of the harm of toys to children. If the lead content exceeds the standard, long-term exposure will cause harm to children
    the
    . Therefore, the accuracy of the determination of total lead content in toy paint is very important. This paper discusses the methods in the national standard GB/T 22788-2008 "Determination of total lead content in toy surface coating".1 Assay Principle
    Samples with thick nitric acid and hydrogen peroxide, using heat plate heating wet method or microwave digestion, dissolved solution at 283.3 nm wavelength, using flame atomic absorption spectrometer or other suitable instruments to determine lead content under suitable conditions.2 Experimental part
    2.1 Raw materials
    nitric acid (ρ -1.42 g/mL), pure analysis; Hydrogen peroxide (ρ s 1.11 g/mL), pure analysis; nitric acid (1 s 99); nitric acid (5 s 99); lead standard solution (100 mg/L): national secondary standard substance, Shanghai Institute of Metrology and Testing Technology.
    2.2 Instrument equipment
    warian AA220 atomic absorption spectrometer; controlled thermoelectrelectrient heating plate with a maximum operating temperature of not less than 200 degrees C; and analytical balance with an accuracy of 0.1 mg.
    2.3 Atomic Absorption Spectrometer Conditions
    Wavelength: 283.3 nm; Lamp current: 8 mA; Slit: 0.5 nm; Acetylene flow: 1 L/min; Air flow: 3.5 L/min.
    standard solution series: 2.0 mg/L, 5.0 mg/L, 10.0 mg/L, 20.0 mg/L, 30.0 mg/L.
    2.4 Analysis step
    national standard GB/T 22788-2008 Original method: said to take samples of about 0.2 g, accurate to 0.1 mg, placed in a 50 mL berries. Add 7 mL nitric acid (ρ x 1.42 g/mL), cover the surface dish, heat on the electric plate to keep the solution slightly boiling and dissolve 15 min. Remove the beo bowl from the heat plate and cool for about 5 min. Slowly drop and add 2 mL of hydrogen peroxide (ρ x 1.11 g/mL) and heat again on the electric plate. If the sample is not fully dissolved, remove the slightly colder and add 1 mL nitric acid (ρ x 1.42 g/mL) and 5 drops of hydrogen peroxide (ρ x 1.11 g/mL) to continue heating. Repeat this procedure 1 time to dissolve the sample completely, until the residual solution is about 1 mL, remove and cool to room temperature. Diluted with about 10 mL of water, the solution is filtered into a 25 mL capacity bottle. Rinse the begum and filter paper 3 times with 5 mL nitric acid (1 plus 99). The resulting solution is all combined and transferred to a 25 mL capacity bottle, diluted with water to 25 mL, the filter liquid as soon as possible with the instrument analysis. Carry out a blank test with the sample. Water flushing method: the previous steps and the original standard method is the same, only with 10 mL water dilution, and then use deionized water to rinse the beech and filter paper 3 times, filtered solution moved to 50 mL capacity bottle, water dilution to scale, as soon as possible with the instrument analysis. Follow the blank test.3 Test results and analysis
    3.1 different lead content test results analysis
    the selection of different lead content of 3 samples, each sample using the national standard GB /T 22788-2008 method and watering rinse method were measured 2 times, the results of the test can be seen in Table 1.Table
    1 national standard method and water flushing method test results comparison
    by Table 1 can be seen: different lead content samples, the use of water flushing method and national standard test results are very different, water flushing method test results are about 9% higher than the national standard method, which indicates that if only the national standard method flushing, may be part of the sample lead is still left in the cup and filter paper, the results of the test results are low.
    3.2 sample (NIST 2581) test results
    the sample (NIST 2581) is also measured using the national standard method and water-flushing method, each measured 3 times, the results are seen in Table 2.Table
    2 sample using the national standard method and watering rinse method of the test results comparison

    3.3 sample (NIST 2581) pre-treatment filter paper reprocessing test results
    sample (NIST 2581) according to the national standard GB / T 22788-2008 method, with 5 mL nitric acid rinse beech and filter paper, filter paper and then according to the national standard 22788-2008 method before treatment, the results of the filter test table 3.
    Table 3 sample according to the national standard method pre-treatment, filter paper reprocessing test results
    as can be seen from Table 3: the use of national standard GB/T 22788-2008 original method pre-treatment, filter paper and beech there are residual lead not fully flushed out, filtered, filter paper reprocessing test results and the original test results added value close to the standard value.
    3.4 sample (NIST 2581) 25 mL water flushing test results
    sample according to the national standard GB/T 22788-2008 method pre-treatment, and finally filtered to 25 mL capacity bottle, and then rinse the filter paper and be cup with water, but the water consumption can not exceed 25 mL capacity bottle scale line, the test results are seen in Table 4.
    can be seen from Table 4: due to the limited capacity of the 25 mL capacity bottle, the filter paper water is limited, can not fully flush out the lead, the results of the test will be low.4 Conclusion
    The analysis results of several sets of comparative experiments show that the national standard GB/T 22788-2008 method finally increases the use of deionized water flushing this step, the lead in beo cups and filter paper is fully flushed deionized water, the results of the test results are better accuracy and accuracy. In addition, the national standard method filtration using 25 mL capacity bottle due to limited capacity, water flushing volume is limited, can not fully flush out lead, the test results are low, it is recommended to use 50 mL capacity bottle.
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