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An Introduction to Quality Assurance in Analytical Science Dr Irene Mueller-Harvey Mr Richard Baker Mr Brian Woodget.

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Presentation on theme: "An Introduction to Quality Assurance in Analytical Science Dr Irene Mueller-Harvey Mr Richard Baker Mr Brian Woodget."— Presentation transcript:

1 An Introduction to Quality Assurance in Analytical Science Dr Irene Mueller-Harvey Mr Richard Baker Mr Brian Woodget

2 Part 4 - Regulation and Accreditation Contents: Accreditation (slide 3,4) ISO 17025 (slides 5-7) Inter-laboratory proficiency testing (slides 8-11) Evaluating analytical quality (slides 12-13) The presentation contains some animation which will be activated automatically (no more than a 2 second delay), by mouse click or by use of the page down key on your keyboard.

3 Accreditation Accreditation is defined as: Formal recognition that a testing laboratory is competent to carry out specific tests Accreditation Certificate

4 Accreditation – which standard? A number of universally recognised Accreditation systems ISO 9000 applicable mostly to manufacturing & services - emphasis on records and customer service Good laboratory (GLP) and good manufacturing practice (GMP) recognised for pharmaceutical and clinical measurements - emphasis on records, procedures, reproducibility ISO 17025 used by analytical laboratories for work outside the health sector - emphasis on valid data, traceability, comparisons and data recognition in a court of law

5 ISO 17025 Accreditation Guarantee to customers: work to agreed standards Laboratory: independent & stringent assessment Agreed & specified methods used All measurements traceable to national & international standards Main features of accreditation

6 ISO 17025 Accreditation How do you become accredited? 1Install a quality system in the laboratory that complies with the ISO 17025 requirements; 2Decide on the schedule of tests that are to be accredited 3Apply to the United Kingdom Accreditation Service (UKAS); 4Have a Pre-assessment visit from the UKAS assessors; 5Have a formal Assessment visit from UKAS; 6Clear any non-compliances they find; 7Become Accredited for the chosen schedule of tests

7 ISO 17025 Accreditation How do you remain accredited? pay an annual subscription perform satisfactorily in inter-laboratory proficiency tests undergo and pass regular horizontal and vertical audits Mostly concerned with the overall quality management system Will trace sample paths from initial acceptance to final report

8 Inter-laboratory Proficiency Tests food labelling, water quality, animal feeds, pesticide residues. Many laboratory tests are used for international or national standard and regulations, for example: The authorised laboratories must show that their results are comparable with others doing the same tests.

9 Show labs how well they compare with others; Help them to reduce the overall variability in testing; Proficiency Schemes (1) Give the regulatory authorities and consumers confidence that their quality criteria are meaningful Participation in proficiency testing schemes offer the following benefits:

10 all participating labs receive identical samples; a true value is assigned for the result of a test (for example it may be the mean of all participants results); participants do not know the true result before they do the test. Proficiency testing (2) Organisers of such schemes must ensure that:

11 Proficiency testing (3) rank the laboratorys performance by calculating its z-score; identify the laboratories that can produce acceptable results for the test; show divergent laboratories how they need to improve their performance of the test. From the results submitted by the participating laboratories, the organisers can:

12 Calculation of z scores A laboratorys z-score is calculated from: [(x - X)/SD] x = the lab result X = the true or accepted result SD = target value for the standard deviation The best performing laboratories have z values close to zero. The acceptable range is +2 to -2 The graph above shows the z scores obtained by 120 laboratories who participated in a particular proficiency testing scheme

13 Variation of CV with analyte level +10 Concentration 0 -10 -20 -30 -40 -50 -60 +20 +30 +40 +50 +60 · · · · · · · · · · 10 -1 10 -3 10 -6 10 -9 10%0.1%1 ppm1 ppb We can expect a CV to be: approx. 5% at a 1g/l level and approx. 15% at a 0.001g/l level Coefficient of variation (CV) or relative standard deviation (RSD) [ % ]

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