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.