Attenuated total reflection (ATR) is a sampling technique used alongside traditional
infrared spectroscopy, which ultimately qualifies samples to be observed directly in an
either solid or liquid state, without additional preparation. FTIR stands for ‘Fourier-
transform infrared’ spectroscopy: a technique that can be used to procure an infrared
spectrum of either the emission or absorption of a liquid, solid, or gas sample.
An FTIR spectrometer synchronously collects the data of high-spectral-resolution over
an extensive range. This is advantageous over the traditional dispersive spectrometer
which only measures the spectral intensity over a much smaller range of wavelengths at
any one time. The term ‘Fourier-transform infrared spectroscopy’ is based upon the
Fourier transform process, which is required to convert the raw data into spectra.
Primary uses of ATF-FTIR
This technique can be used to analyze biological samples in a cheaper, more
economical manner. The significant cost of substrates is a well-known obstacle when it
comes to the introduction of bio-spectroscopy into routine laboratory/clinical practice. As
a versatile and cheaper substrate, readily available aluminium foil has been shown in
experiments to repeatedly compete with low emissivity, gold-coated, and glass slides
used for cytological and histological specimen analysis by ATR-FTIR.
The featureless/low background signal given off by aluminium foil facilitates the
production of traditional infrared or Raman spectra, without any interference with the
substrate itself, and without sacrificing relevant fingerprint biochemical data of the
specimen – even for incredibly thin samples (i.e. approximately 2 μm).
The aluminium foil has been previously found to behave either just as efficiently as (or
even better than) the low emissivity or gold-coated slides. Albeit transmission FTIR is
not possible on aluminium foil, past studies demonstrate that this foil is a potentially
inexpensive, versatile, and readily available substrate that could one day be suitable for
ATR-FTIR analysis of a variety of biological samples.
To conclude, the characteristics of aluminium foil demonstrated in previous ATR-FTIR
studies could soon promote a progression towards more accessible substrates, some of
which can be readily applied in either clinical or research milieus.