What are common quality control materials used in quantitative LC-MS/MS drug testing?

• A. Commercially prepared quality control materials with known concentrations of target analytes and isotopically labeled internal standards.
• B. Fresh urine samples from staff
• C. Distilled water
• D. Glass beads

Answer: (A)

In quantitative LC-MS/MS drug testing, quality control relies on materials that have known, assigned concentrations of the target drugs and include isotopically labeled internal standards. These QC materials are usually commercially prepared and matrix-matched (often in a urine-like matrix) so they mimic real samples. The known concentrations let you verify the accuracy of the calibration curve and the precision of the run, while the isotopically labeled internal standards co-elute with the analytes and correct for variability in extraction, ionization, and instrument response. Using these well-characterized QC materials at multiple concentration levels helps you detect drift, poor recovery, or matrix effects, ensuring the assay remains reliable over time.

Fresh urine from staff lacks defined concentrations and traceability and raises safety concerns, so it isn’t appropriate for QC. Distilled water has no analytes or matrix and won’t reveal assay performance. Glass beads don’t represent a biological sample or impact LC-MS/MS measurements.