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National Standard of the People's Republic of China Hygienic standard for lead content of pencil coating UDC 686.863.3: 546.815 GB8771-88 The maximum allowable content of pencil coating specified in this standard refers to the relevant provisions of the International Voluntary Standard for Toy Safety compiled by the International Committee of Toy Industries ICTI. The method for determining the lead content refers to IS03856/1-1980 Paints and varnishes - Determination of "soluble" metal content - Part 1: Determination of lead content - Flame atomic absorption spectrophotometry and dithiothreitol spectrophotometry. 1 Subject content and scope of application 1.1 Subject content
This standard specifies the maximum allowable content of lead in pencil paint layers to protect the health of children and adolescents. 1.2 Scope of application
This standard applies to various types of pencils used by primary and secondary school students in my country and pencils produced by the pen-making industry for export. 2 Maximum allowable content of lead in pencil paint layers 2.1 The total lead content in pencil paint layers should not exceed 2500 mg/kg (2500 ppm). 2.2 The maximum allowable content of soluble lead in pencil paint layers should not exceed 250 mg/kg (250 ppm). 3 Determination method
3.1 The atomic absorption spectrometry used to determine the total lead content in pencil paint layers For the photometric method, see Appendix A. 3.2 For the atomic absorption spectrophotometric method used to determine the soluble lead content in the pencil paint layer, see Appendix B. 4 Acceptance rules
4.1 Products should be inspected by the manufacturer, commodity inspection department and health and epidemic prevention department. It should be ensured that all products leaving the factory meet the requirements of this standard. Each batch of products leaving the factory should have a quality certificate. 4.2 Sampling method
Sampling should be carried out in accordance with GB282881 "Batch Inspection Count Sampling Procedure and Sampling Table (Applicable to Continuous Batches)". 4.3 If the inspection results do not meet the requirements of this standard, the relevant production units should jointly select samples from twice the amount of products for re-testing. If the re-test still does not meet the requirements of this standard, the entire batch cannot be accepted. 4.4 If there is an objection to the re-test results and arbitration is required, the arbitration agency can be determined by negotiation between the two parties, and the re-test samples should be taken in accordance with the sampling method and test method specified in this standard. 5 Glossary
Total lead content refers to the total soluble and insoluble lead content detected in the pencil paint layer. 5.2 Soluble pencil content refers to the lead content in the pencil paint layer extracted by a solution with the acidity of human body fluid. Approved by the Ministry of Health of the People's Republic of China on February 22, 1988 640
Implementation on December 1, 1988
A.1 Summary of the method
GB 877188
Appendix A
Atomic absorption spectrophotometry for total lead content in pencil paint layer (supplement)
First clean the surface of the pencil sample, remove the paint layer with acetone, then evaporate the acetone, ash the remaining paint in a high-temperature furnace, and measure the absorbance of lead in a hydrochloric acid medium at a wavelength of 283.3nm in an air-acetylene flame using an atomic absorption spectrophotometer. The measurement range is less than 1%.
A.2 Reagents
Acetone (6 analytical grade).
A.2.2 Hydrochloric acid (1+1): analytical grade, specific gravity 1.19. A.2.3 Lead standard solution:
A.2.3.1 Weigh 1.0000g of metallic lead (99.99%) and place it in a 200mL beaker, add 30mL of hydrochloric acid (A.2.2), heat slightly, dissolve completely, cool, transfer to a 1L volumetric flask, add 10mL of hydrochloric acid (A.2.2), dilute to scale with deionized water, mix well, this solution contains 1mg lead per milliliter.
A.2.3.2 Transfer 50.00mL of lead standard solution (A.2.3.1) to a 500mL volumetric flask, add 10mL of hydrochloric acid (A.2.2), dilute to scale with deionized water, mix well, this solution contains 100ug lead per milliliter. A.3 Instruments
Atomic absorption spectrophotometer, equipped with an air-acetylene burner and a lead hollow cathode lamp. Any atomic absorption spectrophotometer that meets the following indicators can be used.
A.3.1 The absorbance of the highest concentration standard solution among the lowest sensitivity equidistant concentration standard solutions shall not be less than 0.25. A.3.2 Working curve linearity Among the five equidistant concentration standard solutions, the difference between the absorbance readings of the highest and second highest concentration standard solutions shall not be less than 0.7 times the difference between the absorbance readings of the lowest concentration standard solution and the zero concentration solution. A.3.3 The coefficient of variation of the absorbance readings of the highest concentration standard solution and the zero concentration solution obtained after multiple measurements of minimum stability relative to the average value of the absorbance readings of the highest concentration standard solution shall not be greater than 1.5% and 0.6% (see A.7) respectively. The working conditions of the atomic absorption spectrophotometer are shown in A.8.
A.4 Analysis steps
A.4.1 Clean the surface of the pencil with detergent, rinse off the detergent with water, and finally rinse with deionized water and dry. A.4.2 Use a dropper to drip about 20-30 mL of acetone onto 3-4 clean pencils, and let the acetone flow along the pencils into 50 mL of evaporated blood that has been dried to constant weight at 105°C in advance.
A:4.3 Cover the evaporated blood and place it in a 50-60°C water bath. Slowly evaporate the blood so that the blood wall sample is concentrated at the bottom of the blood, and evaporate until dry. A.4.4 Place the blood in a 105°C oven, dry for 10-15 minutes, weigh it, and subtract the weight of the empty dish to get the sample weight. Note: The sample weighs about 0.3-1.0 g, depending on the lead content. A.4.5 Place the dish in a high-temperature furnace, heat it from room temperature to 200°C, keep it at this temperature for 15 minutes, and then continue to heat it to 480±20°C and keep it for 30 minutes to make the sample completely ash.
A.4.6 Add 5mL of hydrochloric acid (A.2.2), heat with a gas lamp to dissolve all the lead, and evaporate to 1~2mL. A,4.7 Use heated deionized water to filter into a 50mL volumetric flask, wash thoroughly with hot deionized water, dilute to the scale, and mix well. A.4.8 On an atomic absorption spectrophotometer, at 283.3nm, in an air-acetylene flame, adjust the zero point with water, and measure the absorbance readings of lead in the test sample and the corresponding standard series solution, and find the corresponding lead concentration from the working curve. A:5 Drawing of working curve
Pipette 0.00, 1.00, 2.00, 3.00, 1.00, 5.00mL of lead standard solution (A.2.3.2) into a set of 100mL volumetric flasks, add 2mL of hydrochloric acid (A.2.2), dilute to the scale with deionized water, mix well, adjust the zero point with deionized water, measure the absorbance reading of lead, and draw the working curve with lead concentration as the horizontal axis and lead absorbance reading as the vertical axis. A.6 Calculation of analysis results
The percentage of lead is calculated according to formula (A1): Lead content (ppm)
Where: C-
The lead concentration is obtained from the lead working curve, ug/mL; the volume of the solution during the determination, mL;
The sample weight, g.
A.7 Calculation of minimum stability coefficient of variation
The coefficient of variation of the absorbance of the highest concentration standard solution and the zero concentration solution is calculated as follows: Sc
Wherein: Se
/E(CC)
/2(O-0)
Percent coefficient of variation of the absorbance of the highest concentration standard solution; Percent coefficient of variation of the absorbance of the zero concentration solution; Absorbance of the highest concentration standard solution;bzxz.net
Average absorbance of the highest concentration standard solution; Absorbance of the zero concentration solution;
Average absorbance of the zero concentration solution;
Number of measurements.
A.8PE2380 atomic absorption spectrophotometer working conditions parameters Wavelength, nm
Lamp current, mA
Slit, A
Air flow, L/min
Acetylene flow, L/min
（A3)
Bi Method Summary
GB8771—88
Appendix B
Atomic absorption spectrophotometry for soluble lead content in pencil paint layer (supplement)
First clean the surface of the pencil sample and dry it. Dissolve the paint layer with acetone and evaporate to remove the acetone. After grinding the paint layer, add 0.07 mol/L hydrochloric acid 50 times the weight of the sample to extract it. Then use an atomic absorption spectrophotometer to determine the absorbance of lead in an air-acetylene flame at a wavelength of 283.3 nm. The determination range is below 1%. B.2 Reagents
Hydrochloric acid: 0.07mol/L.
B.3 Apparatus
B.3.1 Oscillator: 280r/min.
B.3.2 Grinder.
B.3.3 Atomic absorption spectrophotometer (same as Atomic absorption spectrophotometry for total lead content in pencil paint layer A.3). B.4
Analysis steps
B.4.1 After the sample is treated according to steps A.4.1A.4.3 of the total lead atomic absorption spectrophotometry, remove the paint remaining at the bottom of the evaporated blood with a blade or pliers and crush it to pass through a 0.5mm sieve. B.4.2 Weigh 0.1-0.5g of the sample and put it into a stoppered dry colorimetric tube. B.4.3 Use a burette to quantitatively add a hydrochloric acid solution (B.2.1) equivalent to 50 times the weight of the sample. The temperature of the solution is 23±2℃. Cover, oscillate for 1h, and leave it for 1h.
B.4.4 Dry filter, use an atomic absorption spectrophotometer at a wavelength of 283.3nm, in an air-acetylene flame, adjust the zero point with 0.07mol/L hydrochloric acid, measure the absorbance of lead in the sample and the corresponding standard series solution respectively, and find the corresponding lead concentration from the working curve.
B.5 Calculation of analysis results
Same as Appendix A Atomic absorption spectrophotometry for total lead content in pencil varnish layer A.6. Additional notes:
This standard was proposed by the Ministry of Health.
This standard was drafted by Shanghai Municipal Health and Epidemic Prevention Station, Shanghai Medical University, and Shanghai Import and Export Commodity Inspection Bureau. The main drafters of this standard are Xu Suen, Zhu Ruiying, and Ma Kejing. This standard was reviewed and approved by the School Health Standards Subcommittee of the National Health Standards Technical Committee. This standard is interpreted by the Institute of Child and Adolescent Health of Beijing Medical University, the technical unit entrusted by the Ministry of Health. 643
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