Overview
ISO 3750:2006 specifies a flame atomic absorption spectrometric (AAS) method for the determination of magnesium content in zinc alloys. The method is applicable to the zinc products defined in ISO 301 and ISO 752 and is suitable for magnesium mass fractions between 0.002 % and 0.08 %. The procedure covers sample dissolution, preparation of calibration solutions, instrumental measurement at 285.21 nm, and calculation and reporting of results.
Key topics and technical requirements
- Analytical technique: Flame atomic absorption spectrometry (flame AAS) with an air/acetylene or nitrous-oxide/acetylene flame; recommended slightly reducing flame for better sensitivity.
- Wavelength: Magnesium line at 285.21 nm.
- Sample preparation:
- Typical test portion: 5 g weighed to 0.001 g.
- Dissolution in a freshly prepared hydrochloric/nitric acid mixture (specified proportion), evaporate to syrup, dilute and transfer to volumetric flasks.
- Use lanthanum (5 % solution) as a matrix modifier.
- All glassware cleaned with boiling aqua regia prior to use.
- Calibration:
- Series of calibration solutions covering magnesium mass fractions: 0.00, 0.01, 0.025, 0.035, 0.05, 0.06, 0.07, 0.08 %.
- For specific products (ZL6, ZP0610) include additional low-level calibration points 0.002 % and 0.005 %.
- Zinc and aluminium matrix solutions are added to calibration flasks to match matrix effects.
- Instrumentation:
- Atomic absorption spectrometer with premix burner; optical path length 5–10 cm.
- Alternate readings for calibration and test solutions to ensure stable instrument settings.
- Precision and performance:
- Precision data derived from interlaboratory trials are provided (repeatability and reproducibility limits vary with magnesium content).
- Reporting:
- Test report shall identify sample, method reference, individual and mean magnesium content (mass %), unusual occurrences, deviations, date, lab identity and responsible signature.
Applications and typical users
- Applications:
- Quality control and acceptance testing of zinc ingots and casting alloys.
- Certification and composition verification for zinc-based products.
- Metallurgical R&D, failure analysis and process control where low-level magnesium content affects properties.
- Who uses it:
- Accredited chemical laboratories and metallurgical testing facilities.
- Production QC teams in zinc foundries and alloy manufacturers.
- Instrument vendors and method validation teams.
Related standards
- ISO 301 (zinc alloy ingots intended for casting)
- ISO 752 (zinc ingots)
- ISO 20081 (sampling of zinc and zinc alloys)
- ISO 5725 series (accuracy, repeatability and reproducibility of measurement methods)
Keywords: ISO 3750, zinc alloys, magnesium determination, flame AAS, atomic absorption spectrometry, chemical analysis, metallurgical quality control, magnesium content.