ISO 11352:2025 PDF

Water quality — Estimation of measurement uncertainty based on validation and quality control data

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Title (English):

ISO 11352:2025

Water quality — Estimation of measurement uncertainty based on validation and quality control data

Document status:: Active
Format:: Electronic (PDF)
Number of pages:: 38
Publication date:: September 1, 2025
Edition:: ISO IS 11352 edition 2 version 1
ICS:: 13.060.45

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Description (English):

This document specifies approaches for the estimation of measurement uncertainty of chemical and physicochemical methods in single laboratories based on validation data and quality control data obtained within the field of water analysis. However, this approach can also be used in many other areas of chemical analysis. NOTE 1 The principles of the estimation of uncertainty specified in this document are consistent with the principles described in ISO/IEC Guide 98-3. In this document, the quantification of measurement uncertainty relies on performance characteristics of a measurement procedure obtained from validation and the results of internal and external quality control. NOTE 2 The approaches specified in this document are mainly based on Nordtest TR 537[ REF Reference_ref_4 \r \h 3 08D0C9EA79F9BACE118C8200AA004BA90B0200000008000000100000005200650066006500720065006E00630065005F007200650066005F0034000000 ], but also QUAM[ REF Reference_ref_5 \r \h 4 08D0C9EA79F9BACE118C8200AA004BA90B0200000008000000100000005200650066006500720065006E00630065005F007200650066005F0035000000 ], and Eurolab TR 1/2007[ REF Reference_ref_3 \r \h 2 08D0C9EA79F9BACE118C8200AA004BA90B0200000008000000100000005200650066006500720065006E00630065005F007200650066005F0033000000 ]. NOTE 3 This document only addresses the evaluation of measurement uncertainty for results obtained from quantitative measurement procedures. The uncertainties associated with results obtained from qualitative procedures are not considered.

Technical details

Technical committee: ISO/TC 147/SC 2 - Physical, chemical and biochemical methods
SKU: ISO 11352:2025

Abstract

Overview

ISO 11352:2025 - Water quality - Estimation of measurement uncertainty based on validation and quality control data - provides a practical, top‑down framework for estimating measurement uncertainty for quantitative chemical and physicochemical methods used in water analysis. Designed for single laboratories, it uses validation results and routine internal/external quality control data to quantify both random and systematic components of uncertainty. The approach is consistent with ISO/IEC Guide 98‑3 and is largely based on Nordtest TR 537 (with input from QUAM and Eurolab TR 1/2007).

Key topics and requirements

Scope and applicability: Applies primarily to quantitative measurement procedures in water analysis; approach can be adopted in other chemical analysis areas. Qualitative procedures are excluded.
Top‑down methodology: Emphasizes using existing validation and routine quality control data rather than a full bottom‑up component analysis.
Data sources for uncertainty estimation:
- Validation studies (for initial estimates)
- Internal quality control (control charts, pooled standard deviations)
- External quality assessment / interlaboratory comparisons
- Reference materials and recovery experiments for bias assessment
Precision and bias assessment:
- Evaluation of within‑laboratory reproducibility (intermediate precision)
- Procedures for estimating bias from certified reference materials and participation in proficiency tests
- Updated requirement for reproducibility data (noted change from a minimum of 8 to 20 replicates for components except first estimations)
Uncertainty calculation:
- Combining within‑laboratory reproducibility and bias into a combined standard uncertainty
- Deriving an expanded uncertainty using an appropriate coverage factor
- Guidance on initial estimation and reporting of uncertainties
Supporting material:
- Annexes covering range division for constant absolute vs relative uncertainties, pooled standard deviation estimation, and worked examples

Practical applications and users

ISO 11352:2025 is essential for:

Environmental and water-testing laboratories needing robust, defensible uncertainty statements for chemical and physicochemical analytes
Quality assurance managers and laboratory directors preparing reports for regulatory compliance or accreditation (e.g., ISO/IEC 17025)
Analysts and method developers who require routine, data‑driven uncertainty estimation without advanced metrology expertise
Regulators and third‑party auditors evaluating method performance claims and measurement traceability

Benefits include clearer reporting of result reliability, improved method validation workflows, and alignment with international metrology guidance.

Related standards

ISO/IEC Guide 98‑3 (GUM principles)
Nordtest TR 537 (basis for the top‑down approach)
QUAM and Eurolab TR 1/2007 (supporting guidance)
ISO/IEC Guide 99 (VIM) and ISO Guide 30 (reference materials)

Keywords: ISO 11352:2025, measurement uncertainty, water quality, validation data, quality control data, within‑laboratory reproducibility, bias estimation, combined standard uncertainty, expanded uncertainty.

Related standards

Mentioned in the description and other ISO standards

Abstract

Overview

Key topics and requirements

Scope and applicability: Applies primarily to quantitative measurement procedures in water analysis; approach can be adopted in other chemical analysis areas. Qualitative procedures are excluded.
Top‑down methodology: Emphasizes using existing validation and routine quality control data rather than a full bottom‑up component analysis.
Data sources for uncertainty estimation:
- Validation studies (for initial estimates)
- Internal quality control (control charts, pooled standard deviations)
- External quality assessment / interlaboratory comparisons
- Reference materials and recovery experiments for bias assessment
Precision and bias assessment:
- Evaluation of within‑laboratory reproducibility (intermediate precision)
- Procedures for estimating bias from certified reference materials and participation in proficiency tests
- Updated requirement for reproducibility data (noted change from a minimum of 8 to 20 replicates for components except first estimations)
Uncertainty calculation:
- Combining within‑laboratory reproducibility and bias into a combined standard uncertainty
- Deriving an expanded uncertainty using an appropriate coverage factor
- Guidance on initial estimation and reporting of uncertainties
Supporting material:
- Annexes covering range division for constant absolute vs relative uncertainties, pooled standard deviation estimation, and worked examples

Practical applications and users

ISO 11352:2025 is essential for:

Environmental and water-testing laboratories needing robust, defensible uncertainty statements for chemical and physicochemical analytes
Quality assurance managers and laboratory directors preparing reports for regulatory compliance or accreditation (e.g., ISO/IEC 17025)
Analysts and method developers who require routine, data‑driven uncertainty estimation without advanced metrology expertise
Regulators and third‑party auditors evaluating method performance claims and measurement traceability

Benefits include clearer reporting of result reliability, improved method validation workflows, and alignment with international metrology guidance.

Related standards

ISO/IEC Guide 98‑3 (GUM principles)
Nordtest TR 537 (basis for the top‑down approach)
QUAM and Eurolab TR 1/2007 (supporting guidance)
ISO/IEC Guide 99 (VIM) and ISO Guide 30 (reference materials)

ISO 11352:2025 PDF

Technical details

Abstract

Overview

Key topics and requirements

Practical applications and users

Related standards

Related standards

Abstract

Overview

Key topics and requirements

Practical applications and users

Related standards

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