How to Handle and Clean Optical Cells

For any spectroscopic experiments, properly cleaned cells are essential. After you’ve used the cells, it’s required to clean them so they’re ready for the next application. (This guideline covers both standard quartz cuvettes and air-free cells.)

PPE stands for personal protective equipment. Lab coat, safety glasses or goggles, and nitrile gloves are all required. Handling concentrated hydrochloric acid requires the use of a fume hood.

Hazards

Shattering an optical cell can result in wounds, so be careful. Using flammable solvents like methanol and acetone might result in a laboratory fire. To avoid inhaling these solvents, use them in the hood. Hydrochloric acid in concentrated form can cause burns and irritate the airways. Wear gloves and only open the bottle in a fume hood that is fully functional.

Optical Cells Cleaning

Empty the cell first, then dispose of the contents in the proper container.

If the cell just has clean solvent (no sample)

Rinse it 2–3 times with the same solvent, then 3 times with acetone and 3 times with methanol after emptying the cell. When doing so, make sure the cell is entirely filled with solvent. Allow it to dry naturally; air-free cells must be tightly clamped for this.

For the cells that contained samples (i.e., something other than solvent)

Rinse the cell 2-3 times with the solvent you used to produce your sample (the solvent should appear clear when you’re through – some more concentrated solutions may require more rinses). If you spill any sample on the exterior of the cell, wash it.

Fill the cell (including the long neck) with a diluted HCl solution after rinsing it once with water. You have two choices here:

• a) dilute 3 drops of concentrated HCl in 20 mL DI water;
• b) use a previously prepared 0.05 M HCl solution (if you use optical cells frequently, produce this solution ahead of time and store it in a wash bottle).

Allow at least 15 minutes for the cell to rest.

The diluted HCl solution should be dumped down the drain, and the cell should be rinsed five times with DI water, which should also be poured down the drain.

Rinse the cell three times with acetone, then three times with methanol. After that, clamp it and let it dry naturally.

General Instructions

If you used a Kontes valve, clean it with solvents (first the same solvent, then acetone, and finally methanol).

Wipe the outside with lens paper and isopropanol after the cells are clean. Never use kimwipes or dry lens paper.
To produce a 0.05 M HCl solution, combine 3 mL concentrated HCl with 500 mL DI water in a 500 mL final volume.

Important guidelines for cleaning

• Extreme temperature fluctuations should be avoided
• Ultrasonic waves should be avoided. The cuvettes may be broken by high energy density and/or undesirable frequencies. Cuvettes consisting of a variety of materials (glass, metal, etc.) are particularly vulnerable. Cavitation eats away at polished surfaces and renders them useless.
• The cleaning solution should not be left in the cuvette at such a high temperature that it evaporates. The increased concentration and high pH value may cause damage to the glass’s surface.

Suggestions when handling cuvettes

• Our precision cuvettes are constructed of glass or quartz glass and contain all of the benefits and drawbacks of these materials. We recommend cleaning, drying, and storing the cuvettes in cases as soon as the measuring process is completed.
• Do not store the cuvettes open in corrosive environments, and do not expose the polished windows to liquids for long periods of time. This might cause deposits or stains to develop on the polished surfaces, leaving the cuvettes useless.
• Cuvettes should never come into touch with anything composed of hard materials, such as glass or metal, to prevent scratching the precision-polished windows.
• Inserting cuvettes into a metal cuvette holder requires caution.
• When filling cuvettes with liquids with a pipette, never let the pipette touch the polished window.
• Cuvettes should never be carried or held with metal tweezers or pliers.
• Although an empty cuvette may be cooled to a few degrees Kelvin without shattering it. The identical cuvette may rupture when filled with water and chilled to only a few degrees below the freezing point owing to water expansion.

Cuvettes with stoppers require special instructions

If the internal pressure of liquid-filled cuvettes with stoppers rises, they may break. The expansion of the liquid in the cuvette owing to a rise in temperature is the most typical cause of such an increase in pressure. This might be as a result of:

• the external source of heat, such as thermal conduction via the cuvette holder
• there is a chemical reaction
• radiation is absorbed in the liquid solution

Taking the following precautions to help prevent stopper cuvette breakage:

• Fill the cuvette just to the point where the light beam may travel through the liquid without being obstructed. If the temperature rises, the liquid will expand into the remaining air volume.
• If the cuvette is filled to the rim, loosen the stopper to allow any surplus liquid to escape.
• If you push the stopper into place, the cuvette will certainly be damaged.
• Stoppers with a capillary hole should be used.