interference

**Interference** in analytical metrology is **any signal or effect that causes the measurement result to differ from the true value of the analyte** — encompassing spectral overlaps, chemical reactions, physical effects, and memory effects that bias or corrupt the analytical signal. **Interference Types** - **Spectral**: Overlapping emission lines, mass-to-charge ratios, or absorption bands — different elements produce similar signals. - **Chemical**: Matrix components react with the analyte or change its chemical form — altering the analytical response. - **Physical**: Differences in viscosity, surface tension, or transport properties between sample and standards. - **Isobaric (ICP-MS)**: Different elements have isotopes at the same nominal mass — e.g., ⁴⁰Ar⁴⁰Ar⁺ interferes with ⁸⁰Se⁺. **Why It Matters** - **False Positives**: Spectral interferences can cause apparent contamination that doesn't exist — costly false alarms. - **Correction**: Mathematical correction, collision/reaction cell (ICP-MS), high-resolution instruments, or alternative isotopes. - **Validation**: Method validation must evaluate interferences for all expected sample types. **Interference** is **signal contamination** — any effect that corrupts the measurement signal and causes the result to deviate from the true analyte value.