Internal standard (IS)
A compound chemically near-identical to the analyte, often a deuterated isotopologue (d3-morphine, d5-EDDP, d5-alprazolam, pyrene-d10), spiked into every sample at a known concentration before extraction. Quantitation is reported as analyte peak area divided by IS peak area, which corrects for losses during clean-up, injection-volume variation and matrix-effect ion suppression at the source.
Explained in these topics
- Sample Preparation, Purification and Instrument Calibration
- Spectrometric Detection: UV-Vis, FTIR and Mass Spectrometry
- SWGDRUG Identification Tiers and the UV / TLC / GC-MS / LC-MS/MS Workflow
- Reference Standards, Certified Reference Materials and the Quantification Baseline
- Ethanol Analysis by GC-Headspace and the Blood-Alcohol Baseline