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Standards Development
The purpose of this document is to describe test plans and the different operating methodologies of these test plans to define and verify the acceptable length of stability of a substance in a sample under specified conditions of preservation (temperature, matrix, light, addition of a stabilizer, where appropriate, type of preservation, etc.) before starting analytical protocols.
It is necessary to have an analytical method with performances that have already been characterized (repeatability, intermediate precision, trueness, accuracy and uncertainty) in order to perform the stability study and implement its test plans.
This proposal answers the request of the ISO/TC147/SC6 experts (ISO/TC147/SC6/N_614, recommendation Sydney 7) for harmonization of practices in assessment of the stability of substances or physico-chemical parameters.
Harmonized and reliable data on stability are essential for the expression of recommendations both in a normative framework and in a regulatory framework. A common methodological framework will enable laboratories to produce reliable data for sharing, pooling and, if possible, banking. These data will feed the recommendations for sample preservation given both in ISO 5667 3, ISO 5667-15 and ISO/TC147/SC2 analytical standards.
The document is applicable to all kind of physico-chemical parameters: organic micropollutants, inorganic and organometallic micropollutants, nutrients and macropollutants, and to all kind of matrices in the aqueous environment: drinking water (DW), surface water (SW), groundwater (GW), urban and industrial wastewater (WW) and solids related to aqueous matrices: suspended solids (SS), sediments, sludge.
It covers sampling operations, transportation and storage before starting analysis. The objective is to carry out tests allowing to study the variations of the value of a given parameter between an initial time (for example spiking of the sample) and a final time, by working on representative samples of the scope of the measurement method. The conclusions of this study make it possible to determine the maximum allowable time before analysis (MATBA), under the conditions of the study.
The stability study is based on 6 steps:
• Define the need (parameters, matrices, concentration levels, storage conditions, storage duration, Maximum Accepted Deviation criterion for the stability study (MADs))
• Definition of the experimental design (type of study, number of tests, time steps)
• Performing tests
• Data validation
• Evaluation of results (based on MADs)
• Expression of stability as a MATBA associated with the conditions and criteria of the study.
The study of the stability shall cover different stages of the analytical process according to the organization of the measurement chain. Examples of organization of sampling and measurement steps linking are given.
Goal 3: Good Health and Well-Being for People
Goal 6: Clean Water and Sanitation
Goal 11: Sustainable Cities and Communities
Goal 13: Climate Action
Goal 14: Life Below Water
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