ATR Prism Selection Criteria

June 10, 2019

Introduction

ATR method is used to analyze the sample surface within 1~2 μm in depth. The measurement is collected when the ATR prism is in contact with the sample. In ATR method, the penetration depth of light into the sample for total reflection depends on the RI of prism and sample, incidence angle and wavelength. In addition, measurement range and durability depend on the material of the prism. Features of each prism are shown as follows.

Prism RI (n1) Penetration Depth dp*1
(1000cm-1)
RI of Sample (n2)*2
for Total Reflection
Measurement Limit
in Low Wavenumber*3
Range
ZnSe 2.4 ~ 2.0 μm <= 1.7 ~550 cm-1
Diamond 2.4 ~ 2.0 μm <= 1.7 ~400 cm-1 *4
Ge 4.0 ~ 2.0 μm <= 2.8 ~650 cm-1
Prism Feature of
Prism
Suitable Sample Non-Suitable Sample Notes
ZnSe Good
throughput
General organic
substance
Hard powder, acidalkaline,
high RI
sample
In case of hard
powder or hubbly
sample, diamond is
recommended
Diamond Intensity,
durability,
measurement
Hard powder, General
organic substance
High RI sample Poor S/N ratio in the
region around 2000
cm-1, due to internal
absorption
Ge Analysis for
high RI sample
Sample including carbon Hard powder, acidalkaline Weak absorption
due to small depth of
penetration

*3 Case of measurement using ATR PRO 450-S, standard FTIR.
*4 If the measurement is needed in the wavenumber range below 400 cm-1, please contact local JASCO distributor.

Experimental

Figure 1. Suitable measurement example using ZnSe and Ge prism.
Sample: ethanol

Keywords

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

References

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