Page 195 - Chalcogenide Glasses for Infrared Optics

Glass Pr ocesses for Other Applications 171

FTIR sample area

Plano/convex
Amtir lens

Extruded Amtir rod
Beam Beam
out in

C1 fiber

C1 IR fiber or ATR fill
extruded Amtir rod O-ring

FIGURE 7.13 AMI fi ber or extruded rod used with FTIR for ATR analysis.

sensor lenses are facing one another in the sampling area. They are
focused on the ends of a C1 fiber or the ends of an extruded C1 rod.
In use, the rods have 45° bevels on each end. The fiber is unclad, or
cladding is removed in the lower loop area and hangs down into a
small chamber containing first the fluid, followed by the fluid with
sample. The arrangement is ideal for this operation. The fiber is very
inexpensive such that it may be used only once and then discarded.
The extruded rod would be a little more expensive. The rod may
be used straight as shown in the cell in the bottom illustration.
Another way would be with mild heat to bend the rod in the same
configuration as the fiber. In that case, the rod would probably be
used more than once. It would cost a few dollars, perhaps $10, while
the fiber may cost $1 to $2. The method produced good results.
However, the companies that would supply to the users were all
instrument companies. Their ATR plates could cost $1000 or more.
There was no advantage to the supplier to furnish such an inexpen-
sive replacement. We were unable to develop a market for our units.
First use of chalcogenide glass fibers made possible what is
referred to as remote spectroscopy. That is, the fiber allows the removal
of reactants away from the FTIR, out of the small sampling areas pro-
vided in each instrument. Further, complicated optics are not required
to move the energy from the instrument to the reaction under study.
The instrument energy is easily focused into the fiber to the reactor,