Transmission using IR Sampling Cards. These
accessories are very often used to conduct transmission
analyses. A microporous sampling substrate that is
chemically inert or resistant and usually non-hydroscopic
is utilized. The microporous sample substrate permits
rapid solvent evaporation when the sample is applied
as a solution. The two most popular types of cards
are polytetrafluoroethylene cards which provide an
absorption free background from 4000-1400 cm-1 and
polyethylene substrates which provide an absorption free
background for the entire spectrum except in the region
of 3000-2800 cm-1. Using these two cards in combination
allows full transmission scanning of the spectral range
from 4000-400 cm-1. Because they are disposable, use of
the IR cards typically shortens analysis time, eliminates
cross contamination concerns, and reduces solvent
clean up waste. IR cards allow the analysis of a wide
range of samples, including but not limited to inorganic
and organic liquids of low volatility, solids that can be
solubilized in volatile solvents, insoluble solids, semisolids,
pastes, lubricants, paints, etc.
Compressed Pellets. Another widely used technique for the