Overview
ISO 13933:2014 specifies a validated analytical procedure for the determination of calcium (Ca) and magnesium (Mg) in iron, cast iron, steel and alloyed steel using inductively coupled plasma atomic emission spectrometry (ICP‑AES / ICP‑OES). The method covers sample dissolution (acid digestion and fuming), calibration, instrumental criteria and calculation of mass fractions. Applicable measurement ranges are Ca: 0.0005 % to 0.006 % and Mg: 0.0005 % to 0.20 % (mass fraction).
Key technical topics & requirements
- Principle: dissolution of a test portion in a mixture of hydrochloric, nitric and hydrofluoric acids with subsequent fuming using perchloric acid; final dilution, optional filtration and nebulization into an ICP spectrometer.
- Analytical wavelengths: suggested lines include Ca 393.66 nm and Mg 279.55 nm; choice of wavelength must be verified for sensitivity and interference on each instrument.
- Internal standard: recommended yttrium (Y) lines (e.g., Y 371.03 nm or Y 360.07 nm) to correct for instrumental drift and matrix effects; internal standard must be free of interferences in the sample.
- Instrument performance criteria:
- Bandwidth (resolution) < 0.030 nm for chosen wavelength.
- Short‑term precision (RSD) ≤ 1% at 100–1 000× LOD and ≤ 5% at 10–100× LOD.
- Calibration linearity: correlation coefficient > 0.999.
- Limits: Ca LOD 0.003 mg/L, LOQ 0.010 mg/L; Mg LOD 0.004 mg/L, LOQ 0.014 mg/L (as specified).
- Reagents & standards: use analytical‑grade acids, water per ISO 3696, certified Ca/Mg stock and working standards and a low‑contamination pure iron for blanks/checks.
- Apparatus: ICP spectrometer (simultaneous or sequential with internal standard capability), PTFE digestion beakers, 0.22 μm PTFE/polycarbonate filters, class A volumetric glassware.
- Safety note: perchloric acid fuming poses explosion/health risks; follow lab safety and ventilation requirements.
Practical applications
- Routine chemical composition control in steel and cast‑iron production.
- Quality assurance and acceptance testing for alloy specifications where low levels of Ca and Mg affect mechanical properties or downstream processing.
- Failure analysis and metallurgical investigations where trace Ca/Mg influence inclusion control, solidification or machinability.
- Regulatory compliance and third‑party material certification laboratories.
Who should use ISO 13933:2014
- Steelmakers, foundries and alloy producers
- Metallurgical and materials testing laboratories
- Quality control and R&D teams performing trace element analysis
- Certification bodies and conformity assessment labs requiring standardized ICP methods
Related standards
- ISO 14284 - Sampling and sample preparation for chemical analysis of steels and cast irons
- ISO 3696 - Water for analytical laboratory use
- ISO 385 / 648 / 1042 - Laboratory volumetric glassware specifications
Keywords: ISO 13933:2014, ICP‑AES, ICP‑OES, calcium determination, magnesium determination, steel analysis, iron analysis, acid digestion, LOD, LOQ, internal standard, yttrium.