QUALITY SYSTEMS, QUALITY CONTROL GUIDELINES AND STANDARDS, METHOD VALIDATION, AND ONGOING ANALYTICAL QUALITY CONTROL - High-Throughput Analysis for Food Safety - page 86

3.5 ONGOING ANALYTICAL QUALITY CONTROL

3.5.1 Internal Quality Control

IQC procedures are used to check the performance of the methodology in use.
Wherever possible, each batch of samples analyzed should include some form of IQC
monitoring to give feedback on both the method and analyst performance. Obviously,
there needs to be a balance between the risk associated with things going wrong with
the analysis and the level of the IQC included with each set of samples. The key to an
effective IQC regime is the availability of QC samples that can be taken through the
whole analytical process. Where available, the quality control material should be
included with each batch of samples and the results assessed against the determined
acceptable range of the material. This range should be established by the analysis of at
least 20 samples. Data collected from the QC samples should, where possible, be
graphed to identify any shifts or trends in the results. Where QC samples have failed,
the decision-making process of acceptance or rejection of the samples associated with
the QC sample should be clearly documented, particularly if the decision is made to
accept their results and not reanalyze the samples. Table 3.3 lists the minimum
frequencies of recovery checks that are required for screening method performance
verification.

3.5.2 Proficiency Testing

Participation in independently organized PTs provides laboratories with an assess-
ment of their own analytical performance and how this compares with others. For
many laboratories, participation in relevant PTs is a mandatory requirement of their
accreditation service and their customer(s).
Pro

ciency test providers have to organize each test in accordance with the
international pro ciency tests standard, ISO/IEC 17043. This standard ensures

that the homogeneity and stability of the test materials are satisfactory so that
participating laboratories know that they will be receiving representative samples

Table 3.3. Minimum Requirements for Method Performance Verification in Routine Use

Method Performance Indicators Other Analytes

Number of
analytes

At least 10 analytes per detection
system covering all critical points
in the method

All analytes that are included in the
validated scope of the method

Frequency Every batch of samples At least every 12 months, but

preferably every 6 months

Level Screening detection limit Screening detection limit

Criterion All method performance indicator

analytes should be detected

All validated analytes should be
detected

Source : Ref. [16].