ISO 4940:2025

Overview

ISO 4940:2025 specifies a flame atomic absorption spectrometric (FAAS) method for the determination of nickel content in steel and cast iron. The method covers nickel mass fractions from 0.002% to 0.5% and defines sample preparation, reagents, instrument performance criteria, calibration and reporting requirements. This second edition updates references, adds guidance on solution preparation and a bibliography, and replaces ISO 4940:1985.

Key Topics and Requirements

• Principle: Dissolve the test portion in appropriate acids, evaporate to fuming with perchloric acid, nebulize the final test solution into an air/acetylene flame, and measure atomic absorption of nickel at 232.0 nm or 352.5 nm (use 232.0 nm when sensitivity at 352.5 nm is insufficient).
• Scope: Applicable to nickel contents of 0.002% to 0.5% (mass fraction).
• Reagents and standards: Prescribes preparation of acid mixtures, a 1 g/L and 0.04 g/L nickel standard, and an iron base solution (40 g/L) to match matrix effects.
• Sample size: Test portion typically about 1.0 g; perform parallel blank tests using pure iron.
• Instrument performance criteria:
  • Limit of detection for nickel in a similar matrix: < 0.15 µg/mL.
  • Characteristic concentration: < 0.40 µg/mL.
  • Precision: specified standard-deviation limits for repeated absorbance measurements.
  • Calibration linearity: slope requirements across concentration ranges; bracketing or calibration curves are described.
• Safety: Handling and evaporation of perchloric acid must be in suitable fume cupboards; follow manufacturer instructions for flame operation and wear eye protection.
• Annexes: Annex A (precision data) and Annex B (procedures for instrumental criteria).

Applications and Who Uses It

ISO 4940:2025 is intended for:

• Metallurgical and chemical testing laboratories performing compositional analysis of steels and cast irons.
• Steel and foundry quality-control teams verifying nickel content for alloy specification, heat treatment behavior, corrosion resistance and material certification.
• Third‑party inspection and certification bodies that require standardized, traceable nickel determinations. Practical use includes routine batch testing, production monitoring, acceptance testing, and regulatory compliance where accurate nickel quantification is required.

Related Standards

• ISO 14284 - Sampling and preparation of samples for determination of chemical composition (referenced for sampling/sample prep)
• ISO 3696 - Water for analytical laboratory use
• ISO 648, ISO 1042 - Laboratory glassware specifications

Keywords: ISO 4940:2025, FAAS, nickel determination, steel testing, cast iron analysis, flame atomic absorption spectrometry, nickel content, analytical method, laboratory quality control.