Overview
ISO 10153:1997 defines a validated curcumin spectrophotometric method for the determination of boron in steel. The procedure covers sample dissolution, decomposition of boron compounds, complex formation with curcumin in a buffered acetic medium and spectrophotometric measurement at 543 nm. The method is applicable to boron levels from 0.0001 % to 0.0005 % (m/m) for low‑boron unalloyed steels and 0.0005 % to 0.012 % (m/m) for steels with higher boron content.
Key Topics
- Principle: Dissolve the sample in hydrochloric and nitric acids; decompose boron compounds by heating with orthophosphoric and sulfuric acids at about 290 °C; form an orange curcumin–boric acid complex in a buffered acetic medium and measure absorbance at ~543 nm.
- Reagents & standards: Use analytical‑grade, low‑boron reagents and ISO 3696 grade 2 water. Key reagents include curcumin solution (1.25 g/L in acetic acid), boric acid standard solutions, ammonium acetate/acetic acid buffer, and fluoride solution for compensation.
- Apparatus & materials: Avoid boron‑containing glassware; use polypropylene or quartz vessels rinsed with acetic acid. Spectrophotometer must be set for 543 nm with 2 cm cells. Use class A volumetric glassware per ISO 385‑1, ISO 648 or ISO 1042 where applicable.
- Sampling & sample mass: Follow ISO 14284 for sampling. Use chips <1 mm. Typical test portions: ~1.00 g for low boron levels and ~0.50 g for higher boron or steels with >30% combined Ni+Co.
- Quality control & calibration: Prepare calibration solutions from the boron standard and build a calibration curve plotting net absorbance vs. micrograms of boron. Use a blank (pure iron) and a fluoride‑treated compensation solution to correct interferences. Net absorbance is derived by subtracting blank and compensation contributions.
- Precision: Interlaboratory studies and statistical treatment were performed in accordance with ISO 5725 (parts 1–3) to establish repeatability and reproducibility limits.
Applications
- Routine quality control of boron in commercial and engineering steels
- Material verification during production or acceptance testing
- Laboratories requiring a documented spectrophotometric method for trace boron analysis
Related Standards
- ISO 14284 - Sampling and preparation for chemical analysis of steels and cast irons
- ISO 3696 - Water for laboratory use
- ISO 385‑1, ISO 648, ISO 1042 - Laboratory glassware specifications
- ISO 5725 (parts 1–3) - Accuracy (trueness, precision) of measurement methods
Keywords: boron determination, curcumin spectrophotometric method, ISO 10153:1997, steel analysis, spectrophotometry 543 nm, calibration, quality control, repeatability, reproducibility.
