Sample Cell Assembly
To obtain an IR spectrum of your sample, you will need to first assemble the sample holder shown above using your sample. Pay close attention to the position of orings and NaCl windows and be careful ....the apparatus is fragile.
Sample Holder: Parts
Collect the parts for the sample cell.
These materials can be found in boxes near the two IR spectrophotometers. Usually, the cell plates, orings and retaining nuts are all loosely assembled. The NaCl windows are hygroscopic and must be stored in a desiccator to keep them dry.
Remove
the desiccator lid by carefully sliding
it off to the side.
Do not place the lid face down on the lab counter. The grease that coats the lid to make an airtight seal will become contaminated (and it would be a mess to clean up!!)
Remove
the petri dish that contains the NaCl
windows.
The NaCl windows are found in the desiccator in a petri dish protected by cotton. These windows are VERY FRAGILE and must be handled with care. THEY WILL BREAK IF DROPPED and CANNOT BE REPAIRED. WORK OVER A TABLE!!
Close the desiccator. Leaving it open over a long period of time will damage the desiccant and the remaining salt windows
Always
wear rubber gloves or finger guards
when handling
the NaCl windows.
The NaCl windows are fragile and sensitive to moisture. Use gloves or finger guards to protect them as you assemble the sample cell. Also, work over a table. That way if you do drop the windows (please don't by the way), they will fall only a short distance and may not break.
First,
position
a rubber oring on the cell plate.
The rubber orings are used to cushion the salt windows when they are squeezed together by the cell's retaining nuts. Without these orings, the windows will break
Carefully
place
one of the NaCl windows on top of the oring.
Remember to use gloves and work over the table.
Place
2-3 drops
of the sample on the NaCl window
Be absolutely sure that the sample is dry. I mean DRY!!! If there is moisture in the sample you are checking it will be absorbed by the NaCl window. This will make the window cloudy and dramatically affect the spectrum you hope to obtain.
Carefully
place
the second NaCl window on top of the sample
The sample will now spread out to form a thin layer between the two salt windows. No pushing is necessary, gravity will be fine
Position
the
remaining rubber oring over the second NaCl window.
The orings must be in place. Without them the uneven stress produced as you tighten the retaining nuts will surely crack the windows. DON'T FORGET THE ORINGS!!!
Place
the second
cell plate on top and install retaining screws.
Don't begin to tighten the retaining screws until all of them are in position. Uneven tightening will produce uneven pressure on the salt plates thus breaking them
.
Gently
tighten
the retaining screws.