Overview
ISO 4939:2016 specifies a dimethylglyoxime spectrophotometric method for the determination of nickel in steel. The method covers nickel mass fractions from 0.10 % to 2.0 % and defines sample preparation, colour development, spectrophotometric measurement and result expression. It is intended for analytical and quality-control laboratories performing nickel determination in steel using a spectrophotometer.
Key topics and technical requirements
- Principle: dissolution of a test portion in hydrochloric, nitric and perchloric acids followed by formation of a coloured nickel complex (nickel(III)) with dimethylglyoxime (DMG) in an ammoniacal medium containing iodine/potassium iodide; measurement at about 535 nm.
- Sample and reagents: typical test portion ~0.5 g; acid mixture (HCl/HNO3/water), perchloric acid, ammonium citrate, iodine/iodide solution, dimethylglyoxime solution and ammonia. Use grade‑2 water and analytical‑grade reagents.
- Procedure highlights:
- Dissolution and controlled evaporation to perchloric fumes, oxidation of chromium if present.
- Take aliquots (25 ml) of the prepared solution for colour development and for a compensating solution.
- Add ammonium citrate, iodine solution, then dimethylglyoxime to develop colour; use an ammonia-treated compensating solution to zero the spectrophotometer.
- Measure net absorbance at ~535 nm in an appropriate optical path cell (1 cm or 4 cm, or as specified for concentration range).
- Establish a calibration curve by plotting net absorbance vs. nickel concentration (µg/ml) using prepared nickel standard solutions.
- Interferences: cobalt, copper and manganese can interfere; the standard gives limits for aliquot selection to minimize their effect.
- Precision: repeatability (r) and reproducibility (R) limits are provided (e.g., r ranges from 0.010 % at 0.1 % Ni to 0.034 % at 2.0 % Ni; R ranges from 0.013 % to 0.053 %).
Applications and users
- Intended for metallurgical and chemical analysis laboratories, steel manufacturers, third‑party QC and inspection labs, and standards laboratories that need validated nickel quantification in steel.
- Useful in production quality control, material certification, alloy verification, failure analysis and compliance testing.
Related standards
- Normative references cited in ISO 4939: ISO 648, ISO 1042, ISO 3696, ISO 14284 (laboratory glassware, water for analysis, sampling).
- Use in conjunction with general precision guidance such as ISO 5725 for repeatability/reproducibility interpretation.
Keywords: ISO 4939, nickel determination in steel, dimethylglyoxime spectrophotometric method, spectrophotometric measurement 535 nm, calibration curve, interferences cobalt copper manganese, precision r R, analytical method for steel.
