Deviating Samples - EcoResponse

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Guidance From Laboratory Committee of the European Co-operation for Accreditation

Following guidance from The Laboratory Committee of the European Co-operation for Accreditation (EA LC) to member accreditation bodies including the United Kingdom Accreditation Service (UKAS), focus on the handling of potentially deviating samples has been strengthened.

UKAS Issued Guidance & Policy Statement

UKAS have issued their own guidance and ‘Technical Policy Statement 63: UKAS Policy on Deviating Samples’ to assist laboratories. Compliance will be assessed during UKAS visits to all accredited laboratories.

What is a Deviating Sample?

Deviating samples (or non-conforming) are defined as those which may have been compromised in some way during sampling, transportation, storage or analysis, and which may cause the integrity of the data to be questioned.
Examples of deviating samples include:
  • Date (and time) not provided for soils (and waters)
  • Sample taken in wrong container
  • Inappropriate headspace present (e.g. Volatiles)
  • Preservation not undertaken
  • Holding time exceeded on receipt
  • Holding time exceeded in laboratory
  • Deviation from method
  • Quality control check failure and sample cannot be repeated
  • Sampling dates must be provided for every sample to enable assessment against holding times for each test. The time of sampling is also required for waters for tests with very short holding times.

Deviating Sample Holding Time

A holding time is the maximum time a parameter is stable from sampling to commencement of analysis, provided sampling criteria has been met. Holding times are determined from referenced methods or in-house stability trials. Holding time information also includes details of sample containers, special instructions and any preservation requirements.

Use of Correct Sampling Containers

The use of correct sampling containers is critical for preserving the integrity of the samples. Advice is available for the correct containers to use and specific instructions for use for all analyses. Where chemical preservation (fixing) is required, pre-dosed sample containers can be provided.
Holding time information also includes details of any specific preservation required. This may be chemical preservation (fixing) or temperature control. This generally applies to waters where chemical fixing is often required. In practical terms, to prevent samples deviating, it is important that:
  • Correct sample containers are used for each test
  • Any special sampling instructions are followed, e.g. fill container to eliminate headspace
  • Sample preservation is carried out where required
  • Sampling dates (and times for waters) are provided
  • Analysis is scheduled within the specified holding times for each test

Should a self-sample kit be requested it is the customers responsibility to ensure samples are taken with the above guidelines in mind. Within all reports where a self sample was taken, deviating sample information will be included. Where a deviating sample is analysed, the test report shall clearly state the reason and that the validity of the test result may have been compromised.

Some of the changes may have an impact on your working practices and we look forward to working together to ensure we meet these requirements.
Please do not hesitate to contact us for further information or any advice required by calling 0800 0305051.

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