Coworkers in another lab have Perkin Elmer Spectrum GX model with ATR attachment and seems to be working fine, it's an older spectrometer, but quite sensitive.

I also hed privilege of seeing in action Nicolet iS10 FT-IR Spectrometer from Thermo-Scientific and was mighty impressed with the specifications as well as with performance.

The sensitivity in the 10 to 20 micrometer range corresponds to wavenumbers 1000 to 500 per cm. However, the sensitivity in this rage depends strongly on the type of crystal/prism you are using in your ATR unit. The spectral range and the cut-off at low wave number depends on the material: zinc selenide (ZnSe) approx. 550 per cm; diamond 350; KRS-5 (thallium iodide/thallium bromide 300. Very often ZnSe is used in ATR units, but this does probably not fall into your range of interest. Diamond might be ideal, but it is expensive, whereas KRS-5 is relatively soft.

To what do you relate sensitivity ?

(A) To surface concentration (G) in terms of microgram per square cm (cm2) ?

(B) Or to thickness d ?

(A) e.g. for proteins ATR-FTIR using Si or Ge trapezoidal interrnal reflection elements (IRE) in a setup with 12 reflections is able to detect surface concentrations down to G = 0.01 microgram/cm2, which is below a monolayer of most proteins.

(B) e.g. for thin polymer films ATR-FTIR is able to detect e.g. PNIPAAM brush films onto Si IRE with thicknesses below d = 10 nm

If you like you may have a look e.g. in our recent article:

M. Müller, B. Torger, E. Bittrich, E. Kaul, L. Ionov, P. Uhlmann, M. Stamm

In-situ ATR-FTIR for characterization of thin biorelated polymer films

Thin Solid Films 2014, 556, 1-8.

DOI:10.1016/j.tsf.2013.12.025

Best regards,

Martin Müller

To my answer of before:

Those surface concentrations and thicknesses related to the amide band region, which corresponds to around 6 micrometer.

Since depth of penetration increases with wavelength, at your wavelengths of 10-20 micrometers sensitivity of ATR-FTIR is even higher.

Best regards,

Martin Müller

Dear followers,

I didn't expect so many good answers. First of all thank you.

I think I should specify my question. I'm developing a novel ATR crystal (three reflections at the sensing surface) on silicon basis. Therefore I'm looking for commerical setups to compare my measurements and sensitivities. I have a very short light path, therefore I do not get in to trouble (

In this problem you have two parameters, properties of ATR crystal and the quality of FTIR spectrometer. I believe commercially there is very large amount of FTIR equipment with ATR option. If you want to go to the limit than one should try best FTIR with multipass ATR. One of the most sensitive instruments would be vacuum version of Bruker Vertex 70 (max resolution 0.4 cm-1) or Vertex 80 (max resolution 0.06 cm-1) spectrometers. As far as I know they also have multipass ATR crystals as well

My goal is to compare my ATR crystal somehow to others. It has 3 reflections at the active side and is made out of silicon. I think there are two parameters which define the quality (signal-to-noise-ratio) the number of reflections at the active surface and the length of the lightpath inside of the ATR crystal (absorbtion). Therefore it could be interesting to have different silicon based multireflection elements (MRE) and to compare them to my ATR crystal.

@Justinas: Therefore I'm interested in the properties of the ATR crystal.

Sensitivity is severly limited by the S/N ratio, which, in turn, is dependent on D-star parameter of the detector. The latter might be really different depending on the objective the spectrometer was orderd for: e.g. a "fast" detector (for step- or rapid-scan) will be noisier than the comparable "slow" one; an MCT is much superior to DTGS, etc.

Thus, detectors are an additional variable in your "equation" - do not forget it .... and Good luck

I completely agree with Andrei. The first step is to select a good MCT detector in order to obtain the highest S/N ratio.

I think you both are pretty right to look for a good detector in the first place. If you have the "problem" to compare your self made ATR crystall to already to exisiting systems, it could be trikcky to get some data, which actually have any meaning or are comparable. Therefore I'm still looking for different manufactoreres of ATR-FTIR equipment. I want to make a list of ATR-equipment, which uses multi-reflection silicon elements, becuase at the moment I have absolutly no clue how many manufactoreres are out there. Then I'm able to choose the one which has the highest parameter overlap D-star, etc. ...) with my setup.

I used several instrument from different manufacturers. However, if I recall well, the ATR in all or most instruments was made by Pike Tech. They must be the major, or at least one of the mayor ATR makers.