LimsPulse
Spectroscopy

Near-infrared (NIR) spectrometer

Measures how a sample absorbs near-infrared light (about 780–2500 nm) through glass or plastic, in seconds and without sample preparation. Used with chemometric libraries for raw-material identity testing, blend monitoring and moisture.

  • Pharmaceutical
  • Agriculture & grain
  • Food & beverage
  • Petrochemical
  • Polymers
  • Animal feed
Photo of a Near-infrared (NIR) spectrometer
Photo: Allancik, CC BY-SA 4.0 (cropped), via Wikimedia Commons
TROUBLESHOOTING

Common problems, causes and fixes

Known good material fails library identity
Likely causes
  • • New supplier, grade or particle size not represented in the library
  • • Different packaging film or measurement through a fold
  • • Moisture uptake by the material
  • • Instrument drift since the library was built
What to do
  • • Re-measure on a clean, flat part of the bag or in a vial
  • • Check the performance test and calibration
  • • Investigate and, if justified, add new representative lots to the library under change control
Two different materials both pass as each other
Likely causes
  • • Library uses a simple correlation that cannot separate similar materials
  • • Threshold set too wide
What to do
  • • Use a more selective algorithm (e.g. PCA/Mahalanobis or SIMCA) for that pair
  • • Re-validate specificity with challenge samples
Noisy spectrum
Likely causes
  • • Lamp near end of life
  • • Dirty window or probe
  • • Too few scans or poor contact with the sample
What to do
  • • Check energy and replace the lamp
  • • Clean the window
  • • Increase scans and press the probe firmly
Performance test fails wavelength check
Likely causes
  • • Internal standard contaminated or damaged
  • • Laser or interferometer fault (FT-NIR)
  • • Temperature change
What to do
  • • Clean or replace the standard
  • • Call service
  • • Let the instrument stabilise and repeat
Quantitative predictions biased
Likely causes
  • • Model built on a different instrument or old lamp
  • • Samples outside the calibration range
  • • Changed sample presentation
What to do
  • • Check outlier statistics; do not report outliers
  • • Transfer or update the model
  • • Standardise the presentation method
In LimsPulse · Calibration Management

Keep every NIR in control: usage logs, calibration and maintenance schedules, and automatic blocking of overdue instruments.

See how