Why Surface Condition Matters in NIR Testing
NIR measurements depend on how near-infrared light interacts with the sample surface or near-surface region. If contamination is present, the analyser may measure the contaminant as well as, or instead of, the target material.
Organic residues, oils, moisture, powders, cleaning agents, and process films can create their own absorption features. These may interfere with identification, classification, or quantitative models. Even thin layers can matter if the target measurement is surface-sensitive or if the contaminant has strong NIR absorption bands.
The effect depends on the contaminant type, thickness, coverage, and the application. For reliable NIR results, the sample should be presented consistently and should represent the material used to build the calibration model. Cleaning, mixing, subsampling, repeated scans, or rejecting visibly contaminated material may be appropriate depending on the test method.
Improving Confidence in NIR Readings
For more detail on the method, review PAS’s overview of Near Infrared Spectroscopy technology. To compare suitable instruments, explore PAS’s NIR analysers through Portable Analytical Solutions, or contact our team to discuss sample presentation, contamination risks, and measurement requirements.