Presentation on theme: "An Introduction to Quality Assurance in Analytical Science"— Presentation transcript:
1 An Introduction to Quality Assurance in Analytical Science Dr Irene Mueller-HarveyMr Richard BakerMr Brian Woodget
2 Part 4 - Regulation and Accreditation Contents:Accreditation (slide 3,4)ISO (slides 5-7)Inter-laboratory proficiency testing (slides 8-11)Evaluating analytical quality (slides 12-13)The presentation contains some animation which will be activatedautomatically (no more than a 2 second delay), by mouse click or by useof the ‘page down’ key on your keyboard.
3 Accreditation Accreditation is defined as: Formal recognition that CertificateAccreditation is defined as:Formal recognition thata testing laboratory is competent to carry out specific tests
4 Accreditation – which standard? A number of universally recognised Accreditation systemsISO 9000applicable mostly to manufacturing & services - emphasis onrecords and customer serviceGood laboratory (GLP) and good manufacturing practice (GMP)recognised for pharmaceutical and clinical measurements -emphasis on records, procedures, reproducibilityISO 17025used by analytical laboratories for work outside the healthsector - emphasis on valid data, traceability, comparisonsand data recognition in a court of law
5 ISO 17025 Accreditation Main features of accreditation Guarantee to customers:work to agreed standardsLaboratory:independent & stringent assessmentAgreed & specified methods usedAll measurements traceable tonational & international standards
6 ISO 17025 Accreditation How do you become accredited? 1 Install a quality system in the laboratory thatcomplies with the ISO requirements;2 Decide on the schedule of tests that are to beaccredited3 Apply to the United Kingdom AccreditationService (UKAS);4 Have a ‘Pre-assessment’ visit from the UKAS assessors;5 Have a formal Assessment visit from UKAS;6 Clear any non-compliances they find;7 Become Accredited for the chosen schedule oftests
7 ISO 17025 Accreditation How do you remain accredited? pay an annual subscriptionperform satisfactorily in inter-laboratory proficiency testsundergo and pass regular horizontal and vertical auditsMostly concerned withthe overall qualitymanagementsystemWill trace sample paths frominitial acceptance to finalreport
8 Inter-laboratory Proficiency Tests Many laboratory tests are used for international or national standard and regulations, for example:food labelling,water quality,animal feeds,pesticide residues.The authorised laboratories must show that their results are comparable with others doing the same tests.
9 Participation in proficiency testing schemes offer the Proficiency Schemes (1)Participation in proficiency testing schemes offer thefollowing benefits:Show labs how well they compare with others;Help them to reduce the overall variability in testing;Give the regulatory authorities and consumers confidence that their quality criteria are meaningful
10 Organisers of such schemes must Proficiency testing (2)Organisers of such schemes mustensure that: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.
11 Proficiency testing (3) From the results submitted by the participating laboratories,the organisers can:rank the laboratory’s 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.
12 Calculation of ‘z’ scores A laboratory’s z-score is calculated from: -10-8-6-4-22468101Laboratory identity numberz-scoreA laboratory’s z-scoreis calculated from:[(x - X)/SD]x = the lab resultX = the true oraccepted resultSD = target value forthe standard deviationThe graph above shows the ‘z’ scoresobtained by 120 laboratories whoparticipated in a particular proficiencytesting schemeThe best performing laboratories have ‘z’ values close tozero. The acceptable range is +2 to -2
13 Variation of CV with analyte level We can expect a CV to be:approx. 5% at a 1g/l level andapprox. 15% at a 0.001g/l level+60+50+40+30Coefficient ofvariation (CV)or relative standarddeviation (RSD)[ % ]+20+10-10-20-30-40-50-6010%0.1%1 ppm1 ppb10-110-310-610-9Concentration