Identify an Unknown Sample with ATR

Ensure the ATR accessory with diamond crystal is properly inserted into the FTIR spectrometer sample compartment and that the crystal is clean. Verify the accessory is recognized in the Omni software dashboard and confirm the analysis type is set to search mode.

Access the search setup menu to view and confirm library selections. Review or customize the spectral libraries to be used for comparison, optionally creating new libraries from pure reference materials if needed.

Click the background measurement button to scan the clean ATR crystal. The software will acquire and display the background spectrum, which is used to eliminate instrumental and environmental signals from subsequent sample measurements.

For liquid samples, place a single drop on the crystal using a pipette. For solid samples like the plastic piece demonstrated, raise the pressure arm, position the sample, and rotate the knob until it clicks to apply pressure.

Click the sample measurement button to scan the unknown sample. The software rapidly compares the acquired sample spectrum against all selected library spectra and generates a ranked list of best matches with numerical match values.

Review the match results panel showing the top 5 library matches and their values (closer to 100 indicates better matches). Compare the overlaid spectra visually in the spectral pane and use the stack view to examine peak alignment and confirm the sample identity.

If the sample spectrum contains totally absorbing peaks that extend off-scale, access the search setup to exclude those regions from analysis using the region selection tools. Rerun the search to generate improved results without the problematic spectral noise.