3. Attenuated total reflectance (ATR)
spectroscopy is a versatile and powerful
technique for infrared spectroscopy which
enables samples to be examined directly in
the solid or liquid state with out further
preparation
I
4. Internal reflection spectroscopy passes infrared
radiation through an infrared transmitting crystal
of high refractive index greater than the sample,
allowing radiation to reflect in the crystal one or
more times
Provided the refractive index of the prism, is
greater than that of the sample medium, and if
the angle ø is greater than the critical angle, the
infrared light beam will suffers the total internal
reflectance
Attenuated total reflection accessory measures
the totally reflected infrared beam when the
beam comes and contact with a sample
5. In this way, an evanescent wave penetrates
into the sample in contact with crystal,
producing a spectrum of sample
EVANESCENT WAVES :
The infrared radiation interacts with the
sample through a series of standing waves,
called as evanescent waves.
An evanescent wave is a penetrating
electromagnetic field whose intensity quickly
decays as it moves a way from its source
6.
7. When collecting ATR data, samples are run as
%reflectance or log (1/R).
% reflectance equivalent to absorbance
8. CRYSTAL COMPOSITION:
Crystals are typically made of
Germanium (Ge)
Zinc sulfide (Zs)
Silicon
Diamond
AMTIR: germanium, arsenic, selenium
(GeAsSe)
Zinc selenide (znse) or mixed thbr and thl
9. There are a number of crystal materials
available for ATR. Zinc Selenide (ZnSe) and
Germanium are most commonly used
ZnSe scratches quite easily and so care must
be taken when cleaning the crystal. It is
recommended that lint free tissue is used.
10. ANALYSING LIQUIDS:
After the crystal has been cleaned and an
infrared background has been collected, the
liquid is simply poured on to the crystal. The
whole crystal must be covered if performing
a qualitative or quantitative analysis.
11. ATR is an ideal technique for analysing
liquids.
Sample preparation is minimal.
Cleanup is easy and fast.
ATR can be used to analyse non-aqueous
solutions such as oils, lubricants, paints,
glues, solvents, inks, dyes, gels and pastes.
12. ANALYSING SOLIDS:
It is an excellent technique for measuring the
composition of solids.
Some examples of solids are films, fabrics,
paper, hard polymer sheets, glass, rubber.
ATR is an ideal technique for measuring dark
coloured which often absorb too much
energy to be measured by IR transmission.
13. Powder analysis:
Powders are easier to run by ATR than by IR
transmission, because little or no preparation
is required.
This category includes pure samples and
mixtures that are available in powdered
form.
Some examples of pure samples and mixtures
pharmaceuticals and pigments.
14. Biological industries
Pharmaceutical industries
Medicinal industries
Chemical industries includes measurement of
drugs during manufactured by fermentation of
methods, following the kinetics of metabolism of
dietary constituents, investigation of detergents
and cosmetics, or identification of contaminants
in waste water, etc.
Using ATR combined with spectral summation the
infrared spectra of solutes, Very dilute aqueous
solutions can be measured.
16. ATR is an easy to use, fast and versatile
technique for IR sampling.
Solids , pastes, gels, powders, liquid can be
analysed with little or no preparation.
17. Organic spectroscopy by william kemp
http://www.slideserve.com/glenda/attenuat
ed-total-reflection-spectroscopy
http://www.utsc.utoronto.ca/~traceslab/AT
R_FTIR.pdf
https://en.wikipedia.org/wiki/Attenuated_t
otal_reflectance
