The decision about which type of cuvette to choose will depend on the instrument used, on the nature of the application and on the properties of the sample. It is generally important that cuvettes be as transparent as possible for the wavelengths to be measured so not to limit the available linear range of the photometer.
The selection of the equipment necessitates requirements on the cuvette, since it must be compatible with the device. This pertains mainly to the outer dimensions of the cuvette, as it needs to fit into the cuvette shaft, but the height of the measurement windows is also crucial. These must align perfectly with the light path that travels through the instrument. This consideration is particularly relevant for cuvettes that are designed to measure small volumes and that therefore feature very small measurement windows. Common heights of light paths are 8.5 mm and 15 mm.
The next important aspect concerns the measuring wavelengths that are involved in the application at hand. Standard cuvettes made from PMMA, polystyrene or normal glass are only transparent in the visible range. If wavelengths in the UV-range, below approximately 300 nm, are employed, cuvettes made from quartz glass, or a special type of plastic, which provide sufficient transparency in this range, must be used (figure 2).