Isotopically labeled internal standards are used in LC-MS to mitigate matrix effects because:

Isotopically labeled internal standards are used in LC-MS to mitigate matrix effects because:

• A. They behave chemically like the analyte but are distinguishable by mass, compensating for matrix effects and losses during sample prep, enabling accurate quantitation.
• B. They replace the analyte completely.
• C. They always have the same retention time and co-elute exactly.
• D. They are used solely to calibrate the detector.

Answer: (A)