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standards should include the entire range of QC samples, typical specimens,
and atypical specimens.
When calibrating mass spectrometers, consult the instrument's online Help
system for instructions.
Quality control
Routinely run three QC samples that represent subnormal, normal, and
above-normal levels of a compound. If sample trays are the same or very
similar, vary the location of the QC samples in the trays.
Ensure that QC sample results fall within an acceptable range, and evaluate
precision from day to day and run to run. Data collected when QC samples are
out of range might not be valid. Do not report these data until you are certain
that the instrument performs satisfactorily.
You can use TargetLynx software to set quality parameters that incorporate a
range of confirmatory checks to identify samples outside of user-specified or
regulatory thresholds. See the TargetLynx Online help topic "QC Monitor
properties." Data should also be manually inspected prior to the reporting of
any results.
When analyzing samples from a complex matrix such as soil, tissue,
serum/plasma, whole blood, and other sources, note that the matrix
components can adversely affect LC/MS results, enhancing or suppressing
ionization. To minimize these matrix effects, Waters recommends you adopt
the following measures:
•
Prior to the instrumental analysis, use appropriate sample
pretreatment such as protein precipitation, liquid/liquid extraction
(LLE), or solid phase extraction (SPE) to remove matrix interferences.
•
Whenever possible, verify method accuracy and precision using
matrix-matched calibrators and QC samples.
•
Use one or more internal standard compounds, preferably isotopically
labeled analytes.
•
To ensure data integrity, Waters recommends you run QC samples
before and after test samples within a single analysis. Additionally, you
can periodically run known samples as unknowns to verify assay results
for a single analysis.
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July 7, 2014, 715003736IVD Rev. C
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