A cuvette is a kind of laboratory glassware, usually a small square tube, sealed at one end, made of plastic, glass, or optical grade quartz and designed to hold samples for spectroscopic experiments. A good cuvette might hold three milliliters of liquid. Cuvettes may be completely open to the atmosphere or have caps (glass or Teflon ®) to seal them shut. Some cuvettes have a glass barrier that extends 2/3 of the way inside, so that measurements can be taken with 2 solutions separated, and again when they are mixed.
Cuvettes to be used in circular dichroism experiments should never be mechanically stressed, as the stress will induce polarization of the glass and affect the measurements made.
Cheap cuvettes are round and look a lot like test tubes. Disposable plastic cuvettes are often used in fast spectroscopic assays, where time is more important than three digit spectral accuracy.
While some cuvettes will be clear only on opposite sides, so that they pass a single beam of light through that pair of sides (often the unclear sides have ridges or are rough to allow for ease of handling), cuvettes to be used in fluorescence spectroscopy are clear on all 4 sides.
