The solution must be put in a specified format into the light path of a photometer for photometric examinations of liquid samples. The typical choice for this application is cuvettes, which are sample containers with optical windows.
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The solution must be put in a specified format into the light path of a photometer for photometric examinations of liquid samples. The typical choice for this application is cuvettes, which are sample containers with optical windows. The spacing between the optical windows is precisely specified, allowing the sample’s route length inside the cuvette to be determined. Even if only those cuvettes utilized for absorbance measurements in the domain of UV-Vis spectroscopy are examined, the selection of different types of cuvettes is extensive. The square cuvette is the most common, having exterior dimensions of 12.5 x 12.5 mm. Sample quantities ranging from microliters (ultra-micro cuvettes) to milliliters (macro cuvettes) are accommodated in this format.
A cuvette’s typical path length is 10 mm, however there are also cuvettes that give a shorter light path across the sample. Furthermore, cuvettes differ in terms of material, height, and the size of the measuring window.
Types of Quartz Cuvettes and Cells
Cuvettes with standard outside dimensions of 12.5 x 12.5 mm but varied minimum sample volume requirements.
The kind of cuvette to choose will be determined by the instrument being used, the nature of the application, and the sample characteristics. It’s vital for cuvettes to be as transparent as feasible for the wavelengths being measured so that the photometer’s linear range isn’t limited.
Because the cuvette must be compatible with the device, the selection of equipment requires requirements on the cuvette. This mostly refers to the cuvette’s exterior dimensions, as it must fit into the cuvette shaft, although the height of the measuring windows is also important. These must be exactly aligned with the path of light that passes through the instrument. This is especially true for cuvettes that are meant to measure tiny quantities and, as a result, have extremely narrow measurement windows. The most common light path heights are 8.5 mm and 15 mm.
The measurement wavelengths that are involved in the application at hand are the next crucial factor to consider. PMMA, polystyrene, and ordinary glass cuvettes are exclusively transparent in the visible range. Cuvettes constructed of quartz glass or a specific type of plastic that give sufficient transparency in this range must be utilized if wavelengths in the UV region, below about 300 nm, are used.
Differences in absorbance spectra of cuvettes constructed of various materials measured between 220 nm and 400 nm
For those methods that rely on reactions that occur at a given temperature and quantify absorbance over time, heating and efficient temperature control of a sample during the measurement process is critical. In this instance, it is critical that the contact area between the cuvette wall and the temperature-controlled cuvette shaft be as broad as feasible, in addition to the material’s suitable degree of resistance. Certain cuvettes, such as macro-cuvettes, have an advantage in temperature-controlled applications because of these factors.
The nature, amount, and concentration of the material at hand are all factors that will impact the cuvette selection. The material from which the cuvette is constructed is largely insignificant if the sample is based on an aqueous solution. Glass cuvettes, on the other hand, are recommended when organic solvents are involved since they have a stronger resistance than plastic cuvettes.
If just a little amount of sample is available, it may be worth considering repurposing it for further measurements. Single-use plastic cuvettes are advised in this situation. Individually packed plastic cuvettes with the proper purity grade will reduce the possibility of contamination. Cuvettes, which were designed to hold extremely tiny quantities, can also be used.
Because each instrument has a detection limit, the concentration of a sample will also impact the cuvette selection. Double-stranded DNA may be successfully measured up to a maximum concentration of 100 g/ml using a photometer with a linear measurement range of up to 2 A and a path length of 10 mm. Higher concentration solutions must be diluted, or dilution can be mimicked by using a cuvette with a shorter route length. A route length of 1 mm, according to the Lambert-Beer equation, allows for measurements of dsDNA concentrations as high as 1,000 g/mL.
If the nature of the application does not dictate otherwise, the material of the cuvette is another option to consider. Glass cuvettes, in general, provide higher transparency and measurement precision, and they may be reused several times. Plastic cuvettes, on the other hand, are easy and safe to handle. Because plastic cuvettes are only used once and don’t need to be cleaned, potential damage and loss aren’t a concern.