Overview
ISO 16042:2007 provides clear, practical guidelines for the use of certified reference materials (CRMs) in the chemical analysis of iron ores. CRMs prepared and certified in accordance with ISO 11459 are used to verify the trueness of analytical results, to monitor ongoing laboratory reliability and to validate shipment sample analyses used in trade.
This standard is intended to be used alongside related standards for sampling, precision assessment and CRM certification to support robust quality assurance and proficiency testing in laboratories that analyse iron ores.
Key Topics
- Scope and purpose: Use CRMs to verify trueness, demonstrate ongoing laboratory capability and assess proficiency. The use of CRMs for titrant standardization or equipment calibration is explicitly excluded.
- Ore type matching: Select CRMs with mineralogical type and elemental mass-fraction ranges similar to test samples. Producers are encouraged to ensure traded blends are represented by appropriate CRMs.
- Mass-fraction difference: The standard provides a formula to calculate allowable absolute differences between CRM and sample for analyte mass fractions (example provided in Annex A). For example, a sample analyte at 0.235 % gives a CRM range of approximately 0.187 % to 0.283 % (±0.048 %). For total iron (% Fe) it is recommended the CRM not differ by more than ±0.5 % Fe from the sample.
- Test portion extraction: CRMs are typically supplied in 100 g lots with recommended test portions of 0.38 g to 1.00 g. Test portions must be taken by appropriate sample-division (rotary or riffle splitter) with random selection and minimum increments to reduce bias.
- Two-bottle strategy: Perform at least two replicate analyses, preferably from separate bottles, to detect alterations or bottle-specific effects.
- Handling and storage: Rules to avoid contamination or alteration include avoiding magnetic or electrostatically charged tools, not storing CRMs in drying ovens, and following manufacturers' storage instructions.
- Control charts and acceptance: Construct Shewhart control charts per ISO 8258 to identify outliers, trends and runs. The standard provides statistical criteria to judge whether analytical deviations from CRM certified values are significant and prescribes follow-up actions if differences persist.
Applications
- Verification of shipment sample analyses that determine commercial value of cargoes.
- Routine laboratory quality assurance and ongoing monitoring of analytical trueness and precision.
- Inclusion as unknowns in proficiency testing programs to assess laboratory competence.
Related Standards
- ISO 11459 (CRM preparation and certification for iron ores)
- ISO 3082 (sampling and sample preparation procedures)
- ISO 8258 (Shewhart control charts)
- ISO Guide 33 / Guide 35 / Guide 30 (reference material terminology, uses and certification principles)
Using ISO 16042:2007 helps laboratories demonstrate traceable, reproducible analytical performance for iron ore chemistries and supports fair, consistent trade practices through validated CRM use.
