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 (slides 5-7)
Inter-laboratory proficiency testing (slides 8-11)
Evaluating analytical quality (slides 12-13)
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3. Accreditation Accreditation is defined as: Formal recognition that
Certificate
Accreditation is defined as:
Formal recognition that
a testing laboratory is competent to carry out specific tests

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

6. ISO 17025 Accreditation How do you become accredited?
1 Install a quality system in the laboratory that
complies with the ISO requirements;
2 Decide on the schedule of tests that are to be
accredited
3 Apply to the United Kingdom Accreditation
Service (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 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
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 the
following 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 must
ensure 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 -2 2 4 6 8 10 1
Laboratory identity number
z-score
A laboratory’s 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 graph above shows the ‘z’ scores
obtained by 120 laboratories who
participated in a particular proficiency
testing scheme
The best performing laboratories have ‘z’ values close to
zero. 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 and
approx. 15% at a 0.001g/l level
+60
+50
+40
+30
Coefficient of
variation (CV)
or relative standard
deviation (RSD)
[ % ]
+20
+10
-10
-20
-30
-40
-50
-60
10%
0.1%
1 ppm
1 ppb
10-1
10-3
10-6
10-9
Concentration