Overview
ISO 10714:1992 specifies a phosphovanadomolybdate spectrophotometric method for the determination of phosphorus in steel and iron. The method covers phosphorus contents from 0.0010% to 1.0% (m/m) and describes sample preparation, reagent requirements, colour development, extraction and spectrophotometric measurement. It replaces ISO 2732:1984 and includes informative annexes on cooperative test results and precision.
Key topics and technical requirements
- Scope and limits: Applicable to P = 0.0010%–1.0% (m/m). Accuracy at the lower range depends on low levels of interfering elements.
- Interfering elements: Arsenic (As), hafnium (Hf), niobium (Nb), tantalum (Ta), titanium (Ti) and tungsten (W) can interfere. The standard specifies application ranges and test portion masses (Table 1/2) depending on these elements; interferences can be reduced by complexation and using smaller test portions.
- Sample preparation: Dissolution of test portion in oxidizing acid mixture followed by fuming (perchloric acid) and specific steps to oxidize/remove chromium where present.
- Complexation and conversion: Silicon and refractory elements are complexed with hydrofluoric acid and orthoboric acid; phosphorus is converted to the phosphovanadomolybdate complex using ammonium metavanadate and hexa-ammonium heptamolybdate.
- Extraction and measurement: The coloured complex is extracted into 4‑methyl‑2‑pentanone (isobutyl methyl ketone) with citric acid present and measured by spectrophotometry at ~355 nm using a 1 cm cell. Blank tests and daily-prepared reagents are required.
- Calibration and calculation: Calibration graph prepared from phosphorus standards; blank correction applied and phosphorus content calculated from measured absorbance and dilution factors.
- Precision: An international trial (20 laboratories in 12 countries) is reported. Precision assessment follows ISO 5725 (repeatability and reproducibility) and is provided in the standard.
Applications and users
- Who uses it: Metallurgical laboratories, steel mills, quality control and certification labs, chemical analysts and research labs involved in steel and iron analysis.
- Practical uses:
- Routine determination of phosphorus in wrought steels, cast irons and pure iron.
- Quality control during steel production where phosphorus specification compliance is required.
- Inter-laboratory comparisons and method validation using prescribed precision data.
- Why use ISO 10714: Provides a standardized, validated spectrophotometric procedure with guidance on handling interferences, calibration, and reporting-ensuring comparable, reproducible phosphorus results across laboratories.
Related standards
Keywords: ISO 10714, phosphorus determination, phosphovanadomolybdate, spectrophotometric method, steel and iron analysis, phosphorus content, interfering elements, calibration, ISO standards.
