Waters Xevo TQ MS, Operator And Maintenance Manual, Page: 8 / 184

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Calibrating
To calibrate LC systems, follow acceptable calibration methods using at least
five standards to generate a standard curve. The concentration range for
standards must cover the entire range of quality-control samples, typical
specimens, and atypical specimens.
When calibrating mass spectrometers, consult the calibration section of the
operator’s guide for the instrument you are calibrating. In cases where an
overview and maintenance guide, not operator’s guide, accompanies the
instrument, consult the instrument’s online Help system for calibration
instructions.
Quality control
Routinely run three QC samples that represent subnormal, normal, and
above-normal levels of a compound. 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.
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.