How should the cuvettes be cleaned?

This is a frequently asked question with no fixed answer. In fact, it is difficult to find specific published methods. Why are there no established methods?

The reason lies in the variety of samples to be analyzed. Due to the wide variety of analysis samples, a wide variety of corresponding cleaning processes are required. However, as it is unrealistic to describe all methods, it does not help to solve the problem. Therefore, some of the common cleaning methods are described below. These methods can be divided into a few groups. One group uses water as a solvent and the other uses organic solvents.

1) Using water as solvent – After cleaning with purified water, clean with ethanol and store in a dry place. However, for heavier soiling, soak the cells in a commercially available cleaning solution made specifically for cleaning cells (30 to 50°C for about 10 minutes). Then clean the cell with water and soak it in a dilute solution of nitric acid and a small amount of hydrogen peroxide (for about 30 minutes). Finally, wash the cell with distilled water and store the cells dry.

2) Use of organic solvents – After cleaning with the organic solvent used, with ethanol or acetic acid, using the same method as for the aqueous solution described above.

3) In case of persistent dirt, the cell can be lightly rubbed with a cotton swab. Avoid using alkaline cleaning solutions, which can dissolve the glass, or ultrasonic cleaners, which can damage the cell.

What is meant by cuvette or solvent limit?

Measurement wavelength ranges for cuvettes made of different materials

1 cm cuvette material must show no absorption at the measured wavelength. Two materials commonly used for cells are glass and quartz. Polystyrene (PS) and polymethyl methacrylate (PMMA) are mainly used for disposable cells. This indicates which wavelengths the different cell types can be used for. As a result, the measurable wavelength range varies

depending on the cell material. The figure shows the transmission spectra obtained for different cell types using air as the measurement object. It is observed that there is no absorption by the cells in the measurement wavelength ranges indicated in the table.

In addition to the measurement wavelength, there is also the issue of chemical resistance. In addition to being used in strongly alkaline solutions, glass and quartz have very good chemical resistance. However, with resin cells, chemical resistance varies by material, so care must be taken when selecting the cell used for the measurement. Another point to note is that there are slight differences in the optical path lengths of individual disposable cells, which are usually discarded after use. This can lead to errors in the quantitative values.

As glass is opaque in the ultraviolet range, glass cuvettes offer a measurement range of approximately 320 nm to 2500 nm, which is narrower than quartz cuvettes. However, at only several hundred dollars each, they are a convenient and cheaper option than quartz cells when short wavelength measurements below about 320 nm are not required. These cells are usually marked with G.

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