Waters Xevo TQD Operator's, Overview And Maintenance Manual page 10

• 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.
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