Overview
ISO 8466-1:2021 - Water quality - Calibration and evaluation of analytical methods - Part 1: Linear calibration function provides the general framework for establishing and using linear calibration in physicochemical and chemical methods for water analysis. The standard defines how to determine the linear working range, select calibration strategies, calculate analytical results and verify calibration validity so that individual water‑quality method standards can reference a consistent approach.
Key topics and technical requirements
- Determination of the linear working range: guidance on preliminary choice and estimation of the linear range (visual x/y plots, point‑to‑point slope analysis) so the selected range is appropriate for linear regression.
- Calibration strategies: multiple approaches including one‑point and two‑point calibration, external and internal standard calibration, calibration of the total procedure, and standard addition. Each strategy covers establishing the calibration function and calculating results.
- Recovery and internal standard handling: procedures for determining recovery rates of analytes or internal standards and incorporating them into result calculations.
- Calculation of calibration functions: methods for computing linear calibration functions and practical considerations for measurement results.
- Validation and control: strategies for testing calibration validity such as control solutions/samples and testing the slope of the calibration line.
- Informative and normative annexes: statistical guidance (Mandel goodness‑of‑fit, standard deviation and confidence intervals), examples of linearity testing, empirical curvature tests, and weighted regression (weighting 1/x).
Practical applications and users
ISO 8466-1:2021 is intended for routine analytical practice in water‑quality laboratories and for standards authors. Typical users include:
- Environmental and drinking‑water testing laboratories establishing routine calibrations
- Method developers writing or validating analytical procedures
- Accreditation bodies and quality managers defining calibration policies
- Instrument manufacturers and service organizations documenting calibration requirements
- Regulators and environmental agencies requiring standardized result calculation and traceability
Practical benefits:
- Harmonizes how linear calibration is implemented and reported across water‑quality methods
- Supports robust quantification by defining working ranges and when different calibration strategies are appropriate
- Facilitates consistent handling of recovery, internal standards and result computation
Related standards
- ISO 8466 series (other parts cover additional calibration topics)
- ISO 11352 (alternative approaches for estimating measurement uncertainty referenced in the introduction)
Keywords: ISO 8466-1:2021, water quality, linear calibration function, calibration strategies, linearity testing, analytical methods, calibration range, standard addition, external/internal standard.
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