Organics, Stability and Uncertainty - A tale of three working groups

This presentation will aim to summarise the recent work carried out across three distinct working groups covering the organics subcommittee as well as the ad hoc groups responsible for production of guidance documents on both sample stability and uncertainty of measurement estimations for regulatory drinking water analysis.

The work of the organics subcommittee has been at the core of SCA since its inception in 1972 and it's fair to say that the technological advances made in this area in particular have been significant. Until recently the work of the committee had declined but this has seen a resurgence since 2014 with new chairs and members bringing much needed energy back to the group. Recent bluebooks to be published include NDMA in drinking waters by GC-MS and Phenoxy Acid Herbicides in raw and potable waters by liquid chromatography. The current ongoing work on taste and odour compounds and screening methods for both GC-MS and LC-MS will be discussed, together with a look at the future work plan of the group.

The publication of the DWI information letter on sample stability in 2005 on sample stability addressed an issue on a subject where many labs didn't have a great deal of robust data. Subsequent to this many laboratories have invested a lot of resource and effort into producing robust sample stability data independent of each other. In addition, the key reference used by the industry (ISO 5667-3), whilst being an international standard, does contain data of varying robustness. The ad hoc committee on sample stability set up in 2015 was organised to address many of these issues with the aim to share information on sample stability data from across the industry. After careful planning, data from 13 laboratories has been collated and assessed for drinking, surface and ground water matrices across both inorganic and organics parameters. The story of the collection and progress with the publication of the bluebook as a definitive UK reference guide will be discussed.

The recent working group to develop a robust consistent way to estimate uncertainty of measurement (UoM) for regulatory drinking water purposes was set up in response to directive changes that will see traditional precision and bias targets removed and replaced with an overall UoM target for all chemical parameters. This will become mandatory for all DWTS accredited laboratories by the end of 2019. Laboratories already estimate UoM due to the requirements of ISO 17025 but often these have been developed individually and have been shown to potentially produce significantly different outputs. This working group was set up to develop a more consistent approach which continues to follow international standards and provides the regulators with a process that can be compared across laboratories. The presentation will summarise the work of the group and the latest position of the project. The presentation will conclude with a summary of the work of the groups and consider the future ability of the SCA to provide resource to publish guidance in key topics.