LIQUID CELLS comprise two IR transmission windows separated
by a lead spacer which is amalgamated to the windows with
mercury. This construction creates a seal which is perfect
for infrared spectroscopy as it is virtually impervious
to solvents and does not contain anything that could create
spurious absorbances. In most cases sealed cells are sold
with a metal front plate containing 2 Luer fittings for
filling and a back plate for mounting, such as ICL's SL-3
and SL-4 sealed cells. In the case of ICL sealed cells,
there is also an amalgam seal to the front plate of the
cell which we lap optically flat to enhance the quality
of seal. These cells are also available simply as sandwich
cells which comprise just 2 windows (one drilled) and a
mercury amalgamated spacer. The SL-2 sandwich cell contains
2 windows, 1 mercury amalgamated spacer and 1 lead gasket
which is amalgamated to a front plate containing Luer fittings.
Sandwich cells can be used to replace the optics in complete
sealed cells such as the SL-3 and SL-4 or with demountable
cell bodies such as ICL's Precision Demountable Cell (0006-497)
or SL-2 (0006-4153).
CELLS are available in a variety of precise pathlengths
ranging from 0.015mm to 10mm. The pathlengths can be calibrated
to 4 decimal places and matched from cell to cell for consistent
results. The availability of precise pathlengths makes sealed
cells the tool of choice for quantitative analysis of liquids.
Sealed cells can also be reconditioned at modest cost, which
makes them relatively inexpensive. ICL provides a cell reconditioning
THE MERCURY to lead amalgams used to seal these cells
have ideal characteristics for infrared spectroscopy, the
seal will break if too much pressure is applied to it. Since
the volumes and pathlengths of these cells are small, the
simple act of injecting the sample into the cell with a
luer syringe can create enough pressure to rupture the seal,
particularly for cells with pathlengths of less than .05mm.
For flow cell applications where pressure is contemplated,
try one of our high pressure flow cells. ICL's high pressure
sealed liquid flow cells are rated for constant and pulsed
pressures up to 1000 psi.
PROPER METHOD for filling a sealed liquid cell is
to create a low pressure area in the cavity of the cell
using an empty luer syringe while using a second luer
syringe to fill the cell. See Fig. 1. After the empty
luer syringe is attached to the cell, the plunger is drawn
back, thereby creating a low pressure area which will
cause the sample to flow into the cell from the other
luer syringe without the need to depress the plunger of
the sample syringe. To remove the sample, use an empty
syringe and simply pull the plunger out slowly or use
a cell cleaning accessory to create a partial vacuum.
See Fig. 2. It is preferable to both fill and empty the
cell from the lower Luer fitting. ICL's SL-3 and SL-4
cells are designed with this filling technique in mind.
The placement of one of the luer fittings on top of the
cell leaves more space between the 2 syringes making it
easy to pull a partial vacuum with one syringe while filling
the cell with the other syringe. See Fig. 1. The design
also discourages filling the cell from the top which frequently
results in the sample being spilled on the cell windows
while it also facilitates simply turning the cell upside
down and dumping the cell contents out of the top port
without spilling the sample contents on the window.