Attenuated Total Reflectance FTIR (ATR-FTIR)

Attenuated Total Reflectance FTIR

Attenuated-total-reflectance (ATR) is a sampling mode which enhances the Fourier Transformed Infrared Spectroscopy (FTIR) signal obtained from sample surfaces, increasing sensitivity and allowing efficient measurements with minimal sample preparation. Like standard FTIR measurements, ATR-FTIR is used for chemical qualification of a sample from raw optical spectra and is often used to determine organic composition.

Strengths
  • Provides fingerprint identification of functional groups and compounds
  • Extensive reference libraries and standardized quality testing procedures are available to aid data interpretation
  • Capable of analyzing solid, liquid or powder samples
Limitations
  • Most inorganic materials do not exhibit FTIR spectrum
    (carbonates, nitrates, silicates, sulfates DO exhibit FTIR spectra)
  • Samples must not be too transmissive (some glasses) or too reflective (some metals)

Technical Specifications:
Example Outputs Instruments Used Sample Requirements

Learn More:
How ATR-FTIR Works Related Techniques

Example Outputs

Example ATR-FTIR spectrum overlay of sample and library reference signal to validate match for polycarbonate resin material

Sample reference ATR-FTIR spectrum comparing 2 variations of a synthesized thermoplastic polyurethane (S-TPU) generated for use in 3D printed biomedical devices.

From MDPI Open Access Publication: https://doi.org/10.3390/ma12060887
Instruments Used for ATR-FTIR
Thermo Scientific Nicolet 6700 IR Spectrometer

Thermo Scientific Nicolet 6700 IR Spectrometer

2 ATR Accessories Available:

  1. Nicolet Smart Golden Gate Diamond ATR
    • Depth Resolution: 2.03 um at 1000cm-1
    • Low-wavenumber Cutoff: 650 cm-1
    • Refractive Index: 2.4
  2. Harrick VariGATR (Germanium Crystal) ATR
    • Depth Resolution: 0.67 um at 1000cm-1
    • Low-wavenumber Cutoff: 650 cm-1
    • Refractive Index: 4.0

Click to Download Brochure

Sample Requirements
  • Organic solid, liquid, powder, or aqueous samples work best
  • Thin film minimum thickness: 100 nm
How ATR-FTIR Works

For ATR-FTIR, a specialized accessory is incorporated into an FTIR system. This accessory includes an internal crystal which promotes multiple internal reflections of the incident IR beam. The crystal is oriented to be in direct contact with the sample surface, allowing it to absorb photons of characteristic energies, based on its chemical composition. When incoming beams lose photons through absorption in the sample, the reflected light wave will have an attenuated intensity. A spectrometer parses the extent of this attenuation over the entirety of the sampled Infrared (IR) domain. Peaks and unique conformations of the resulting ATR spectrum are then interpreted to yield chemical information about the functional groups and elements present in the sample.

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