Instrumentation

FT-IR

Attenuated Total Reflectance (ATR) sample accessory

Each IR spectrometer is equipped with an ATR sample accessory. These accessories are useful for high throughput labs, like teaching labs, because they can be used with both liquid and solid samples, and samples can be prepared and removed quickly.

The ATR accessory looks like a small platform with an even smaller circular polished crystal at its center. Briefly, you place your sample on top of this small crystal. The spectrometer feeds IR radiation into the crystal from below. Some of the radiation is reflected by the sample back into the crystal and is detected by the spectrometer and converted into an IR spectrum.

Warnings. The ATR accessory, particularly the crystal, is expensive and requires tender, loving care to protect it. Our crystals are made from either diamond (carbon) or germanium (two steps down from carbon in the Periodic Table). They are carefully manufactured and polished to pass IR radiation with as little distortion as possible, but they will be damaged and become useless if you fail to protect them.

  • Do not touch the crystal with your fingers, pipets, or spatulas, if you can avoid it.
  • Do not put corrosive compounds on the ATR (mainly strong acids).
  • Do not put certain organic solvents (acetone, other ketones, chlorinated compounds) on the ATR as they will dissolve adhesives used in the ATR.
  • Never wipe the ATR with a Kimwipe as this will scratch the crystal.
  • If the ATR is equipped with a Pressure Tower (used for solid samples), always keep the Tower rotated to its maximum elevation, tilted back and locked, when not in use. Never leave the Tower in contact with the crystal for an extended period as this can etch, and even crack, the crystal.
  • Always move the Tower carefully keeping one hand on the Tower at all times. Never allow the Tower to drop forward – the tip can crack the crystal.

Quick Guide to measuring and printing an FT-IR spectrum

Detailed instructions for using the IR spectrometer, including applying your sample to the ATR and cleaning the ATR afterwards, can be found in this PDF file.