Overview
ISO 6835:1981 specifies a titrimetric method for the rapid determination of total boron in commercial washing powders (surface‑active agents/detergents). The procedure eliminates phosphate interference by passing an aqueous sample extract through an anion‑exchange resin, converts boron to a boric‑acid–mannitol complex, and determines boron by titration with a standardized sodium hydroxide solution. The standard was prepared by ISO/TC 91 and approved by IUPAC.
Key topics and technical requirements
- Sample preparation
- Dissolve a defined test portion of the laboratory sample in water (35–40 °C) and remove coarse insolubles by filtration.
- Phosphate removal
- Use a strongly basic anion‑exchange resin (quaternary ammonium, Cl– form; 4% divinylbenzene reticulation; 150–300 µm particle size).
- Load filtrate (specified aliquot), pass at 1.0–1.5 ml/min, collect eluate and washings; regenerate the resin with diluted HCl (1 + 4) and water rinses.
- Complex formation and titration
- Adjust eluate pH to ~5.8, add D‑mannitol (to form the boric‑acid–mannitol complex), then titrate with standardized NaOH (c = 0.05 mol/L) to pH 5.80 ± 0.05.
- Standardize NaOH against a known boric acid solution before analysis.
- Control points
- pH control at key stages: pH 3.0 ± 0.1 before loading onto resin; pH 5.80 ± 0.05 for titration endpoint.
- Use calibrated volumetric glassware, burettes and a pH‑meter with glass and reference electrodes.
- Calculation and precision
- Boron (as B2O3) is calculated from the titration volume, NaOH concentration and sample mass.
- Inter‑laboratory precision data are provided (example SDs: repeatability ≈ 0.05–0.08; reproducibility ≈ 0.08–0.14 for typical B2O3 levels).
Applications and users
- Routine quality control and batch testing of commercial washing powders/detergents.
- Regulatory or environmental testing where total boron content is relevant (product labeling, discharge limits).
- Analytical and R&D laboratories in detergent manufacturers, contract testing labs, and standards bodies implementing or verifying boron determinations.
- Useful when sequestrants or complexing agents are present because the method removes phosphate interference.
Related standards
- ISO 607 - Surface active agents and detergents: sample division and storage
- ISO 648 - Laboratory glassware: one‑mark pipettes
- ISO 1042 - Laboratory glassware: one‑mark volumetric flasks
- ISO/R 385 - Burettes
Keywords: ISO 6835, boron content, washing powders, titrimetric method, boric acid‑mannitol complex, anion‑exchange resin, detergent analysis, surface active agents.
Open preview (PDF)Surface active agents — Washing powders — Determination of total boron content — Titrimetric method