ATR Prism Selection Criteria

September 9, 2020



Attenuated total reflectance (ATR) method measures the infrared spectrum of the sample surface depth of 1 to 2 µm when sample and ATR prism are in close contact. Depending on the refractive index of prism and sample, the depth of light penetration into the sample, the measured spectra may differ. In addition, the measurement wavenumber range and durability vary depending on the prism material. The features of each prisms are shown below.

FT/IR-4600 FTIR spectrometer (left) and ATR PRO ONE ATR accessory (right)

Features of each prism

Prism RI (n1) Penetration Depth dp*1
RI of Sample (n2)*2
for Total Reflection
Measurement Limit
in Low Wavenumber*3
ZnSe 2.4 Approx. 2.0 μm 1.7 or less ~500 cm-1
Diamond 2.4 Approx. 2.0 μm 1.7 or less ~350 cm-1 *4
Ge 4.0 Approx. 0.7 μm 2.8 or less ~550 cm-1
Prism Feature of
Suitable Sample Non-Suitable Sample Notes
ZnSe Good
General organic
Hard powder, acidalkaline,
high RI
In case of hard
powder or hubbly
sample, diamond is
Diamond Intensity,
Hard powder, General
organic substance
High RI sample Poor S/N ratio in the
region around 2000
cm-1, due to internal
Ge Analysis for
high RI sample
Sample including carbon Hard powder, acidalkaline Weak absorption
due to small depth of

*3 Case of measurement using ATR PRO ONE and standard FTIR.
*4 If the measurement is needed in the wavenumber range below 350 cm-1, please contact local JASCO distributor.


Example: Diamond is suitable (Sample: Toluene)

Spectra measured with diamond and ZnSe ATR have higher peak intensities than measured with Ge ATR.
Measurements with diamond ATR can be extended down to the low wavenumber side.

Example: Ge is suitable (Sample: Carbon-containing rubber)

Spectra measured with Ge ATR has a flat baseline for a sample with a high refractive index and can be measured without distortion.


280AT0003-E, ATR, prism, diamond, Ge, ZnSe, refractive index


About the Author

Dr. Carlos Morillo received his Post Doc at Advanced Industrial Science & Technology in Fukuoka and was a Research Scientist at Kyushu University in Japan where he lived for several years. Carlos received his Doctor of Engineering from Kyushu University and his Masters and BS from Simon Bolivar University in Caracas Venezuela. He is an Applications Scientist at JASCO.

About the Author

Spectroscopy Group