ISO 4940:1985

Overview

ISO 4940:1985 specifies a validated flame atomic absorption spectrometric (AAS) method for the determination of nickel (Ni) in steel and cast iron. The standard covers sample dissolution, reagent recipes, apparatus and instrument settings, calibration, calculation and reporting. The method is applicable to nickel contents in the range 0.002 % to 0.5 % (m/m) and includes precision data from inter‑laboratory trials.

Keywords: ISO 4940, nickel determination, flame atomic absorption spectrometry, AAS, steel and cast iron, nickel content.

Key topics and technical requirements

• Scope and principle: Dissolve a test portion in acids, evaporate to fuming with perchloric acid, spray the solution into an air‑acetylene flame and measure Ni atomic absorption (primary line 352.5 nm; alternative 232.0 nm if sensitivity is insufficient).
• Reagents: Includes recipes such as hydrochloric acid–nitric acid–water mixture (3:1:2 by volume) and nitric–perchloric acid mixture (100 ml HNO3 + 800 ml HClO4 diluted to 1 L). Use reagents and water of very low Ni content.
• Standards and calibration: Stock Ni solution (1 g Ni/L) and working standard (40 mg Ni/L). Prepare a fresh calibration graph for each series; determine the “zero‑member” concentration by extrapolation before plotting.
• Instrument performance: Specifies detector/wavelength, flame (air‑acetylene, slightly lean), lamp current per manufacturer, bandwidth guidance (352.5 nm: 0.2–0.4 nm; 232.0 nm: 0.15–0.25 nm) and precision criteria for absorbance measurements.
• Detection and characteristic concentrations: Characteristic concentration targets and limits of detection are given for both wavelengths (e.g., limit of detection better than 0.30 µg Ni/mL at 352.5 nm and 0.15 µg Ni/mL at 232.0 nm).
• Safety and cleanliness: Warnings on perchloric acid vapours, acetylene hazards, UV protection and the need to remove perchloric residues from glassware and burner heads.

Practical applications

• Routine chemical analysis laboratories testing steel and cast iron for nickel content (quality control, material certification).
• Metallurgical labs verifying alloy composition for corrosion resistance, mechanical properties and conformity to specifications.
• Regulatory or procurement testing where quantified Ni content in ferrous materials is required.

Who should use this standard

• Analytical chemists and lab managers performing Ni assays by flame AAS.
• Quality assurance professionals in steelmaking, foundries and metal fabrication.
• Third‑party testing labs and organizations issuing material certificates.

Related standards

• ISO/R 377 - selection and preparation of samples for wrought steel (sampling guidance referenced).
• ISO 5725 - precision of test methods (used for inter‑laboratory precision evaluation cited in the standard).

This concise summary helps users quickly understand ISO 4940’s scope, method essentials and practical use cases for nickel determination in steel and cast iron using flame AAS.