GB/T 20975.11-2018 in English

GB/T 20975.11—2018 Standard Overview

National Standard of the People's Republic of China GB/T 20975.11—2018 "Chemical Analysis Methods for Aluminum and Aluminum Alloys Part 11: Determination of Lead Content" is an important specification for the determination of lead content in aluminum and aluminum alloys. This standard replaces the old version GB/T 20975.11—2008, and has made many improvements in the determination range, reagent requirements and analysis methods, especially introducing hydride generation-atomic fluorescence spectrometry (HAFL) as a supplementary means.

Background and significance of standard revision

With the expansion of the application field of aluminum and aluminum alloys, the requirements for the detection of trace elements in materials are becoming increasingly stringent. As an element with potential harm to human body and environment, its accurate determination is crucial for product quality control and environmental compliance. The revision of GB/T 20975.11 is mainly based on the following considerations:

• The scope of application of Method 1 (Flame Atomic Absorption Spectrometry) has been expanded from $0.005\%\sim1.50\%$ to $>0.005\%\sim12.0\%$
• The sample dissolving acid volume table and the high lead content sample processing steps have been added
• The more sensitive hydride generation-atomic fluorescence spectrometry has been introduced, which is suitable for the determination of ultra-low lead content

Comparison of the two main determination methods

Method 1: Flame Atomic Absorption Spectrometry (FAA)

FAA is a traditional and classic method for determining the content of metal elements. Its principle is to use the fact that the absorbance of lead at a specific wavelength ($217.0\mathrm{nm}$ or $283.3\mathrm{nm}$) is proportional to the concentration.

Method 2: Hydride Generation-Atomic Fluorescence Spectrometry (HAFL)

HAFL is a highly sensitive trace element analysis technology, especially suitable for the determination of ultra-low lead content. The principle is to use potassium borohydride as a reducing agent to convert lead ions into volatile hydrides, which are quantified by fluorescence intensity.

Implementation suggestions and precautions

Laboratory selection suggestions:

• For routine detection ($0.005\%\sim12.0\%$), flame atomic absorption spectrometry is preferred because of its simple operation and high efficiency
• For ultra-trace analysis ($0.0001\%\sim0.005\%$), hydride generation-atomic fluorescence spectrometry is recommended to obtain higher sensitivity and accuracy

Quality control points:

• Regularly calibrate the instrument to ensure that the characteristic concentration meets the requirements (Method 1: ≤$0.4\mu\mathrm{g/mL}$; Method 2: detection limit of $0.0001\%$)
• Use standard samples for verification to ensure the accuracy of the analysis results
• Strictly control the blank test value to avoid external contamination

Data recording and reporting:

• Record the sample information, methods used and measurement conditions in detail
• The report should include the measurement results, repeatability error and tolerance
• For abnormal phenomena, analyze the causes and record the treatment measures