Accreditation of radiochemical analyses, from NAMAS to ISO 17025:2005 and beyond

Transcription

1 Accreditation of radiochemical analyses, from NAMAS to ISO 17025:2005 and beyond George Ham Centre for Radiation, Chemicals and Environmental Hazards Health Protection Agency The Analysts Dilemma: Maintaining standards in radiochemistry under future regulation 30 th June 2011

2 Outline My background Accreditation, benefits and difficulties Radiochemistry, benefits and difficulties Method validation Method verification Dangers of the prescriptive approach Different Accreditation Schemes Conclusion

3 My background Nearly 40 years of low level radiochemical analyses of environmental materials About 20 years experience of formal quality assurance. Recent experience of gaining accreditation for two analytical methods (2010) This talk is my personal views on the future

4 Benefits of Accreditation Accreditation gives confidence to customers regulators and others, that as far as possible reported results are correct and traceable to National and International standards It requires all methods to be validated before use and continual verification that they are fit for purpose It may be an essential requirement for some work

5 Accreditation; the Laboratory s dilemma We all have financial constraints The benefits of accreditation to a laboratory must outweigh the effort and financial costs involved Accreditation could impose such high costs it is uneconomic to gain it Fewer laboratories gaining accreditation will lower overall confidence in measurements rather than increasing it

6 Radiochemistry:- particular advantages. Internal tracers lower the sources of uncertainty Radiation counting can be very specific, minimising interferences The random nature of radioactivity means radiochemists have lifetime experience with uncertainties Radiochemistry has a proud history of quality assurance. I have been involved in intercomparison exercise since the first year I joined NRPB ( 40 years)

7 Radiochemistry:- particular difficulties Lengthy analyses and not suitable for automation. Environmental samples include a large number of matrices Few Certified Reference Materials available, particularly in solid matrices Total laboratory throughput for individual analyses are often low Low activities impose long counting times

8 Method validation This is essential but there are difficulties:- The paucity of CRM s The length (and therefore cost) of some methods limits the number of validations that can be performed Spiked matrices and some CRM s are a poor substitute for the real sample There needs to be a risk / benefit assessment Great care needs to be taken to design a validation scheme that is both fit for purpose and cost effective

9 Method verification in practice. CRM s are just too rare to be used for routine validation Maximum use should be made of both internal QC samples and intercomparison exercises. Laboratories that process a large number of matrices can not hope to verify all of them. Again much thought and care is needed to design a cost effective and fit for purpose scheme

10 The prescriptive approach. I hope I have illustrated some of the particular problems This means accreditation schemes should not be too prescriptive It is impractical to apply a verification and validation scheme for an analyses taking hours or minutes in a laboratory processing hundreds of samples a month to an analysis requiring several man days effort over several weeks in a laboratory processing a few tens of samples a year

11 Different Schemes. Different accreditation and regulation schemes can require different schemes of validation and verification etc Surely if an analysis has been accredited to ISO it must be considered as acceptable However specific schemes may need to assess specific things like sampling and required accuracy Increased overheads could lower the number of laboratories performing some work which has implications for overall quality and the future of radiochemistry expertise

12 Conclusions The assurance of accreditation to recognised standards is invaluable I have two concerns for the future: Overly prescriptive requirements, particularly for validation and verification could cause more harm than good Overlapping accreditation schemes could overburden laboratories

13 And finally Lets not forget radiochemists have a proud tradition of quality measurement This is supported by the large number of laboratories who participate in intercomparison and proficiency testing schemes like NPL, Procorad and MAPEP