New specification for contaminated land data

EAGLE (Environmental Analysis Group for Laboratory Excellence) was formed in June 1996 in conjunction with the National Measurement Directorate of the DTI to enable the department to have access to peer groups of commercial analytical laboratories in different market sectors.

The organisations currently participating in EAGLE are: Analytical & Environmental Services; AlControl Laboratories; Chemex International; Bodycote Altech; Harwell Scientifics; East of Scotland Water; ALcontrol Geochem; SAL; Severn Trent Laboratories; EAL; Robertson Laboratories; and Thames Water - WQC.

When analysing soil samples for the range of parameters commonly found in contaminated land, it is generally agreed that the results obtained are dependent upon the methods of analysis used. Currently, methods are not specified in the UK, and therefore considerable variation in results can occur between laboratories, even though they may be using accredited methods.

The above laboratories all participate in proficiency testing schemes, and this group, plus many other laboratories and scientists, have voiced their concern regarding the apparent lack of improvement in the spread of data for soils analysis being reported by the many laboratories involved within the schemes. It was decided, amongst the EAGLE members, that they would compare their data with each other in an attempt to discover the causes of this spread.

It quickly became apparent that small variations in methodology caused significant differences in the data, and once the EAGLE laboratories had agreed on a common method for a particular parameter, a marked reduction in the spread of results was achieved.

Over 70 laboratories participating in the Contest scheme take part in the testing, which covers the analysis of such materials as zinc, arsenic, polyaromatic hydrocarbons; and complex cyanide.

Conclusions
Comparison of the EAGLE data sets with those of the other laboratories participating in the Contest scheme, clearly demonstrates the increased spread of data due to variations in the methods used by different laboratories. It is therefore apparent that the use of controlled methodologies assists in ensuring comparability of results.

Method specification
The EAGLE group has now commenced an initiative to improve the quality of contaminated land analysis by means of an agreed specification.

The principle objective is create a specification which is acceptable to the EA and to the industry. This specification must allow large numbers of samples is to be analysed fairly quickly, to achieve detection limits which comply with current guidelines, to be robust, and able to be implemented by the majority of laboratories - in other words, to be fit for purpose. Whilst the methods will not be as prescriptive as those of BSI or British Gas, all the critical details which are known to cause significant variations will be specified.

The specification will include:

  • A list of methods covered
  • Specification of each method and its critical details
  • Specification for a method validation protocol
  • Method performance targets
  • Proficiency scheme participation (Contest)
  • Proficiency scheme performance targets
  • Provision for reviewing and revising methods and performance targets

The Environment Agency has recently published its policy on qualification requirements for chemical testing, which can be found on its website.

A full version of this edited article was first published in VAM bulletin, issue number 21, 1999.



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