ISO 10697-1:1992

Overview

ISO 10697-1:1992 specifies a standardized flame atomic absorption spectrometry (AAS) method for determining the acid‑soluble calcium content in steel. The part covers principle, reagents, apparatus, sampling, test procedure, calibration, analytical performance (precision, detection limits, characteristic concentration) and reporting. The method is applicable to calcium levels from 0.0005 % (m/m) to 0.003 % (m/m) and uses dissolution in hydrochloric and nitric acids followed by AAS measurement of the 422.7 nm Ca line in a dinitrogen‑monoxide/acetylene flame.

Key topics and technical requirements

• Scope & definition: Acid‑soluble calcium = calcium dissolved in the specified acids (HCl/HNO3).
• Sampling: Follow ISO 377.2 (sampling and preparation of steel samples).
• Reagents & solvents: Analytical‑grade reagents and very low‑calcium water (ISO 3696); potassium chloride/lanthanum nitrate buffer; pure iron diluent with <0.0001% Ca.
• Sample preparation: Dissolution of ~2 g test portion in HCl, addition of HNO3, filtration and dilution; blank test required.
• Instrumentation: AAS with a calcium hollow cathode lamp (422.7 nm), N2O–C2H2 flame, and appropriate background correction. Instrument performance checks include:
  • Limit of detection in matrix similar to final solution: better than 0.02 µg Ca/ml.
  • Characteristic concentration: better than 0.05 µg Ca/ml.
  • Graph linearity and precision checks (manufacturer settings and calibration verification).
• Calibration & calculation: Use multi‑point calibration (including zero member); procedures to account for non‑zero blank absorbance and derive Pcaz for zero correction. Final Ca content expressed as % (m/m) with a defined calculation formula.
• Precision: Inter‑laboratory trial results reported in the standard show repeatability (r) and reproducibility (R) values for representative concentrations (for example, at 0.0005% Ca r ≈ 0.00018% and R ≈ 0.00023%; values increase with concentration).

Applications and users

• Practical uses: Quality control and chemical analysis of steels and alloys where low-level acid‑soluble calcium must be quantified (e.g., melt practice monitoring, impurity control, metallurgical research).
• Who uses it: Metallurgical and materials testing laboratories, steel producers, third‑party inspection labs, R&D groups, and instrument vendors seeking compliant AAS methods and verification criteria.

Related standards

• ISO 10697-2 - Steel - Determination of total calcium content by flame AAS (companion part).
• Normative references in the document: ISO 377.2, ISO 385-1, ISO 648, ISO 1042, ISO 3696, ISO 5725 (precision evaluation).

Keywords: ISO 10697-1, calcium determination, flame atomic absorption spectrometry, AAS, acid‑soluble calcium, steel analysis, calibration, detection limit, precision.