ISO 4942:2016

Overview

ISO 4942:2016 specifies an N‑benzoylphenylhydroxylamine (N‑BPHA) spectrophotometric method for the determination of vanadium in steels and cast irons. The method is applicable to vanadium mass fractions from 0.005 % to 0.50 %. It provides a laboratory procedure for dissolving samples, chemically converting vanadium to a coloured complex, extracting that complex into an organic phase and measuring absorbance at about 535 nm.

Key topics and requirements

• Scope: Quantitative determination of vanadium in steels and cast irons within 0.005–0.50 % mass fraction.
• Analytical principle:
  • Acid dissolution of a calibrated test portion.
  • Addition of orthophosphoric acid to suppress iron interference.
  • Oxidation of vanadium to V(V) with potassium permanganate and controlled reduction of excess permanganate (sodium nitrite + urea).
  • Reaction with N‑BPHA in hydrochloric acid to form a coloured complex followed by extraction into trichloromethane (chloroform).
  • Spectrophotometric measurement at ~535 nm (1 cm cell).
• Reagents & safety: Uses common strong acids (HCl, HNO3, HClO4, H3PO4), KMnO4, sodium nitrite, urea, N‑BPHA in trichloromethane. Note safety warning for perchloric acid (explosive vapours with organics/nitrous fumes).
• Apparatus & glassware: Grade A volumetric glassware (ISO 648/ISO 1042), spectrophotometer with 1 cm cells, separating funnels.
• Test portion & calibration: Test portion sizes depend on expected vanadium content. Calibration solutions are prepared using a vanadium standard in an iron matrix, and a calibration curve (absorbance vs µg/ml V) is used to calculate results.
• Quality controls: Blank tests, parallel calibration, and procedures for sample decomposition and extraction to ensure reproducible colour development.

Applications

• Quality control and specification verification for alloy steels and cast irons where vanadium content affects mechanical properties (hardness, wear resistance).
• Incoming material inspection and batch certification in steel production and foundries.
• Metallurgical laboratory analysis, production process control, failure analysis and R&D where accurate vanadium quantification between 50 ppm and 5 000 ppm is required.
• Useful for laboratories performing routine chemical composition analysis using spectrophotometric vanadium determination.

Who should use this standard

• Metallurgical and material testing laboratories
• Steel and cast iron manufacturers and foundries
• Quality assurance and compliance teams in metallurgy
• Third‑party certification and inspection bodies

Related standards

• ISO 14284 - Steel and iron - Sampling and preparation of samples for chemical analysis
• ISO 3696 - Water for analytical laboratory use - Specification and test methods
• ISO 648, ISO 1042 - Laboratory glassware (pipettes, volumetric flasks)

Keywords: ISO 4942:2016, vanadium determination, N‑BPHA spectrophotometric method, steels, cast irons, spectrophotometer, calibration curve, metallurgical analysis.