Cary 630 FTIR Spectrometer Performance fail

Question

Hello, we own this equipment in the company, and we encountered this problem, who can help, we cant find the cause, or the solution.

Akram Zaki · Accepted Answer

Hi itnick, 
 which accessory / sample module are you using? Depending on the accy (ATR, Transmission, etc.), the value is low (or very low) for S-N. Do you have a KBr engine (blue-ish window) and is it foggy/contaminated with scratches/fingerprints/moisture/droplets, etc? In that case the window, or the detector might need replacement as the result is quite low for SN. 
 Regarding the laser frequency: uncheck the "Check value only" checkbox and retry the Laser Freq test with polystyrene. Now, when the "calculated laser temp. intercept" (RHS bottom of the screenshot you sent) has a new value, click the "Set" button on the right to accept the new value. This recalibrated the laser freq. If you now perform the test again, it should pass.

Akram Zaki · Answer

It can fail the last peak (around 3000 cm-1) because contact with the ATR anvil is not sufficient. The IR through the diamond only has a limited range (I believe it's <25 um), therefore the sample needs to be in direct contact with the diamond. You can do this by adding several "ATR spacers" on top of the polystyrene film, or just simply get a plastic bag / piece of paper / elastic band and place this on top of the polystyrene film and below the anvil. This will increase the signal significantly. Watch the live signal (right before starting the calibration) and make sure the big peak at ~1000 cm-1 has a minimum Abs of approx. 0.9, but often you can get to 1.0-1.2. This means the actual problem (peaks at ~3000 cm-1) have enough signal to get through the laser calibration. 
 Good luck!