Overview
ISO 12744:2006 - "Copper, lead, zinc and nickel concentrates - Experimental methods for checking the precision of sampling" - defines experimental procedures to verify the precision of primary sampling, sample processing, chemical analysis, physical testing and moisture determination for copper, lead, zinc and nickel concentrates. Precision is expressed in terms of standard deviations and the standard is intended to be used in conjunction with ISO 12743 (sampling procedures).
Key topics
- Scope and purpose
- Provides methods to quantify precision of the full sampling-to-analysis chain for metal concentrates.
- Expresses precision as standard deviations for primary sampling, sample processing and analysis.
- Interleaved sampling
- Pairs of interleaved samples (A and B) are formed by diverting alternate primary increments.
- Recommended collection from more than 20 lots of the same concentrate type for reliable results.
- Sample processing methods
- Method 1: Each interleaved sample is split to produce four laboratory subsamples; all analysed in duplicate - allows separate estimation of primary sampling, processing and analytical precision.
- Method 2: Produces three laboratory subsamples with duplicate analyses - provides separate but less precise variance estimates.
- Method 3: Produces two laboratory subsamples analysed in duplicate - yields combined precision for sampling + processing and separate analytical precision.
- Statistical evaluation
- Uses duplicate means, ranges and derived variances (notation R, s1, s2, s3).
- Applies the π/4 factor to relate range to variance for pairs.
- Uses F-tests (95% confidence) to determine if variance components are significantly different and can be partitioned.
- Computes total variance and converts to standard deviations for comparison with target precision.
- Operational guidance
- Analyses should be run in random order by the same analyst on the same day using the same equipment.
- Frequency: repeat checks regularly and after equipment or procedure changes; embed checks in routine sampling due to workload.
Applications
- Quality control and assurance in mining and mineral processing for copper, lead, zinc and nickel concentrates.
- Assay and metallurgical laboratories verifying analytical and sampling performance.
- Contract sampling and trading disputes where quantified sampling uncertainty is required.
- Regulatory bodies and auditors assessing adherence to ISO sampling practice.
Who should use it
- Metallurgical engineers, laboratory managers, mine QA/QC personnel, assay labs, consultants and procurement/contract teams involved in concentrate sampling and valuation.
Related standards
- ISO 12743 - Sampling procedures for determination of metal and moisture content (normative reference).
- Users should consult additional relevant analytical ISO standards for specific chemical or physical test methods.
Keywords: ISO 12744:2006, sampling precision, copper concentrates, lead zinc nickel concentrates, interleaved samples, sample processing, sampling standard deviations, F-test.
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