Quality Control2[1]

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Quality Control in TestingLaboratories

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Quality Control Samples

In every test series should be used acontrol sample

The control sample MUST beindependent from the calibrationsolution!

Examples: Prepared from other chemical Another lot of solution


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Quality control samples maybe:

Standard solutions Ready prepared reference

materials In-house reference materials Certified reference materials

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Use of standards as quality control sample: Only the calibration standard and the stability of

the analytical system is controlled Use of CRM as quality control sample:

The calibration standard and the stability of theanalytical system is controlled

The sample preparation is controlled as well


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Requirements for quality controlsamples:

Long time stability Available in big amounts Concentration of the analyt equal to the

analytical problem Matrix equal to the analytical problem

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Control Charts

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Control Charts

Statistical calculation for the x-chart Pre-period is made by 12 or 20 measurements of

a quality control sample from different workingdays

The average is calculated The standard deviation (s) is calculated 2 s (95% confidence interval) warning limits 3 s (99% confidence interval) control limits


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Control Charts

Use of the X-chart in the daily routine: Every day at minimum the same control sample is

measured If the control sample is measured more than one

time a day All measurements can be used or Always the same has to be used!!

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Control Charts

Out-of-control-situations: One point out of 3 s Two of three points out of 2 s Seven points continuously increasing Seven points continuously decreasing Seven points continuously above the average Seven points continuously below the average Ten of eleven points below / above the average


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Control Charts

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Control Charts


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Control Charts

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Control Charts


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Control Charts

Target Value Chart Range Chart

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R- Chart

Preparation of the Range Chart In every sequence one natural sample is

analysed twice The deviation of the results in % will be put

into the range chart If often the samples give negative results it is

possible to use the quality control sample


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R- Chart

Preparation of theRange Chart

The mean of the rangesis calculated

The upper control limitis

3,267 times the meanof the range forduplicates

2,574 times the meanof the range fortriplicates

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R- Chart

Out of control criteria

One point above the control limit 7 points in a row above the central line 7 points in a row steadily increasing or

decreasing


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Target Value Chart

For the target value chart the targetvalue is used instead of the average ascentral line.

The limits are defined by the laboratory. There should be some objective evidence

for the limits: proficiency test results Limits from normative documents or laws experience

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Target Value Chart

The only out- of control criteria is out of the limits


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Target Value Chart

The target value chart may be used forthe statistical evaluation of the analysis ofcertified reference materials.

In that case it is sufficient if the result ofthe reference material is within the givenlimits of the reference material producer.

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Blank Chart

Where blanks have an significant influenceon the test result, blanks should be

Analyzed daily Documented in a blank chart

For this purpose a X-chart can be used!


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Recovery Chart

If the recovery is analysed on routinebasis, the results can be documented in aRecovery Chart

For this purpose also a X-chart can beused!

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Control Charts

How to react upon out-of-controlsituations??

Stop the analyses

Start root cause analyses Only go on with producing results after

corrective action and when the system is incontrol again

Complete documentation as nonconformingwork may be necessary!!!


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Reference Materials

Periodical use of Certified ReferenceMaterials CRM is necessary.

Use of in-house RM is possible. The used in-house RM should be traceable

to CRM or proficiency tests (PT)

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Reference Materials

The analytes and the matrix analyzed inthe laboratory should be covered by the

CRM available in the laboratory. The available CRM / RM shall be listed


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Reference Materials

The policy of the use of CRM / RM mustbe described in a procedure.

Who is allowed to use RM? Who is responsible? Under which conditions the CRM have to be

stored? How have the CRM to be handled?

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Reference Materials

This policy is very important forlaboratories that use CRM for calibration

of measuring equipment! For them the written procedure must be

very precise (e.g. mechanical testing)


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Reference Materials

In-house RM may be:

Self-made materials Old PT-samples Spiked samples

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Reference Materials

In-house Reference Materials In-house RM should have the following

characteristics: Defined and known values homogeneous Long-time stability Available in a big quantity Matrix should cover the analytical problem


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Reference Materials

COMAR Database for certified reference

materials www.comar.bam.de

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Proficiency Tests

The Proficiency Tests should cover thefield of accreditation in a specified time

period with respect to: Matrix Parameters


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Proficiency Tests

The participation in Proficiency Testsshould mirror the main-fields of the workof the laboratory.

Special regulations of the accreditationbody and governmental requirementsshall be taken in account.

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Proficiency Tests

The laboratory must have apolicy for the participation inproficiency tests.

The participation has to beplanned.

The results of the Proficiencytests have to be listed.


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Proficiency Test Provider

FAPAS several languages, every kind of food,

water, GMO, microbiology, chemistry www.fapas.com

EPTIS Database for PTs

www.eptis.bam.de

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Quality Control2[1]

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