Many biological measurements, the samples are so valuable and a few milliliters of the volume are difficult to target. The required volume can be decreased by making two or four sides of the cuvette inside walls thicker. In a typical research laboratory, the spectrophotometer has a standard chamber size in which a cuvette is accommodated to allow a specific light wavelength to pass through the sample solution. This distance between the cuvette parallel optical windows is accurately manufactured and pre-known, which is known as the cuvette path length.
Cuvettes have a light transmission of a limited wavelength range, have refractive index dielectric mismatch (different refractive index of air and solutions), and can have damages such as scratches which can be very small and unnoticed. All of these factors might affect the outcome experiment measurement.
Quartz material has the highest transmission and temperature resistance most importantly is transparent in both the visible light and UV range and is an appropriate choice when measuring samples in the UV-light spectrum.
Glass and plastic materials are normally transparent to visible light ( 380-700 nm ) but absorb in the UV ( 190 – 340 nm ) wavelength ranges. Therefore, glass and plastic cuvettes are ideal for colorimetric protein assays or measurement of the bacterial culture density, which cannot be used for concentration and purity measurements of samples in the UV ranges. Plastic cuvettes are low-cost and disposable.
Types Of Cuvette
Cuvette depends on the instrument to be used, on the experiment’s nature, and the sample itself. It is important that the cuvettes and cells have an as high transmission as possible for certain measured wavelengths, so we don’t usually limit the material to just the linear range of the photometer. Quartz cuvettes have the highest transmission among all materials.
The requirements of the equipment necessitate the cuvette to be compatible with the instrument. The external size of the cuvette, because it must fit into the cuvette holder, is of major importance, and also take note of the height of the measuring chamber.
Another factor to consider is the light beam position (Z dimension): the light source must be able to pass through the optical window of the cuvettes. This is particularly important to sub-micro volume cuvettes that have very small apertures. The clear windows for light beams could be very small (i.e. 2 mm x 5 mm). If not properly chosen the Z dimension (light height), the micro cuvettes might well not be compatible and cannot be used. Common Z dimensions are 8.5 mm, 15 mm, and 20 mm.
Cuvette Chemical Resistance
The material from which the cuvette is produced is relatively less important when the sample is an aqueous solution. Plastic or glass or quartz cuvettes will all work and you can even choose the most affordable NRC glued cuvettes.
If organic solvents, on the other hand, are involved, glass and quartz cuvettes are the preferred choices because these are more robust compared to plastic alternatives. And the NRC will not work with organic solvents, instead, you should go with CRF or HTR versions.
If only a few samples are available, the reuse of the sample for the following measurements may be considered. In this case, it is recommended to use disposable Plastic Cuvettes The risk of contamination will be minimized if the plastic cuvettes are individually packaged, and have an appropriate purity quality.
Alternatively, sub micro quartz cuvette may be selected which were designed to use with extremely micro cuvette volumes.
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