(FTIR) A Part of the Mirror Is a Little White.

Reason
  It seems to be the result of the heat of the infrared light source for an extended time.

 

Solution

Conduct the performance check according to the power spectrum or the validation program.
If this specification is satisfied, there is no problem for the measurement and you can continue to use it.
If not satisfied, execute the [Auto Adjust] on [Instrument] button once, then perform the performance check again.

 

 

The mirror in the interferometer may become opaque after being used for a long time. This is caused by the heat of the light source. Usually, however, this doesn't cause a problem in a measurement of μm order in the infrared wavelength region.
The FTIR spectrophotometer has several mirrors inside. Never wipe the mirror surface with cloth or cleaner even if these mirrors are contaminated with dust. It may damage the mirror surface and lower the intensity of the infrared signal (the influence is especially large in the short wavelength region), resulting in an adverse effect to the measurement.

 NOTE:
If vapors of any organic halide, such as difluoromethane (CH₂F₂), dichloromethane (CH₂Cl₂), chloroform (CHCl₃), or carbon tetrachloride (CCl₄) enter the interferometer, they are decomposed by the heat of the light source to highly caustic hydrogen halides such as Hydrofluoric acid (HF), Hydrochloric acid (HCl), etc. Mirrors, other optical elements, screws and another parts in the interferometer might be damaged. Please prevent the entry of organic halide vapors into the interferometer by installing a local ventilation system at the FTIR sample compartment, or purging the interferometer with dried air or N2 gas, when you run samples that include volatile organic halide compounds.