Hello,

I would recommend a glass cuvette because they have better solvent compatibility (at least in the case of organic solvents) and a greater temperature range to work with. In addition most commonly used plastics are sensitive to UV-Light there for I would check first wether your cuvette is inteded for uv-measurements.

If your cuvettes are reusable for this kind spectroscopy depends very much on the actual material of the cuvette and the experimental conditions. Which solvent/s are you using, which wavelenght are you using and whats the temperature during the experiment? The yellowish color points to aging of the cuvette. If the UV-Light is the problem, do a blank meausrement of a cuvette without solvent in your nomal measurment atmosphere. If there is a change over time, the cuvette is not usable for this kind of measurment. If you have a stable measurement add the solvent, than then includ step by step the other parameters till you have your experimental set up. Make those measurments over times greater than your usual measurment time. If there are changes during on of the experiments you find the troubling parameter, which you need to change or change the kind of cuvette used.

I hope this is some kind fo help for you.

Generally plastic cuvettes strongly absorb UV, which is why they cannot be used in spectroscopy in the UV range. Readings with UV light are generally done with quartz cuvettes, which show little UV absorbance. They are expensive, however, and certainly not disposable. I take it the UV is to break down remaining substances, not just sterilization? You could try a dilute (1:10) bleach solution. I don't know if it will degrade the polystyrene(?) cuvettes, but you can probably get several runs out of each cuvette.

there is no information on the kind of solvent you used for the dexametasone dissolution. if you use water the plastic UV cells can be used several times without any special UV treatment just washing with acids and distilled water is enough. of course zero the spectrophotometer with the blank containing cell before each measurments

Mark Brandt, 1999 – 2010

http://www.rose-hulman.edu/~brandt/Fluorescence/Absorbance_Spectroscopy.pdf

Cuvettes

Most samples studied using visible and ultraviolet spectroscopy are liquid. The sample must therefore be placed in a transparent container to allow measurement. These containers are called cuvettes.

Cuvettes are generally made from transparent plastic, glass, or quartz. Different cuvettes have different optical properties. Plastic cuvettes are increasingly popular because they do not shatter when dropped, and because their low price makes them disposable. However, plastic cuvettes tend to have considerable absorbance in the ultraviolet. Performing measurements in the far ultraviolet (below ~250 nm) requires relatively expensive (and relatively fragile) quartz cuvettes. The graph below shows absorbance spectra for cuvettes of different composition, where each cuvette only contained water. It is apparent that the plastic cuvettes become opaque in the ultraviolet, and that only the quartz cuvette is useful below about 260 nm.

Fig

Glass cuvettes are also opaque in the ultraviolet; unlike plastic cuvettes, glass cuvettes are effectively identical in physical appearance to quartz cuvettes. An important control experiment therefore involves measuring the absorbance properties of the cuvette to ensure that these properties are appropriate for the experiment. One issue with most spectrophotometers is that the acquisition software allows “zeroing” of the instrument with a sample present. Note, however, that the optical density of the sample is still present: an optical density measurement of zero may result fomr a sample with a high optical density if the instrument is zeroed to the opaque sample. While generating an instrument baseline using air as a sample will alleviate this issue, it must be remembered that air absorbs light at wavelengths shorter than about 210 nm.

A second potential problem with cuvettes is that not all cuvettes have the same pathlength in all orientations. In the spectrophotometer layout below, note that the cuvette has a 1 cm pathlength as drawn. However, if the cuvette were inserted into the instrument in a different orientation, the pathlength would be considerably shorter (about 0.3 cm). Since absorbance depends on pathlength (the “” in A = εcℓ), the absorbance will also be smaller than expected for a sample of a given concentration.

Fig

In addition to interference by the cuvette, solution components may absorb. Molecules containing disulfide bonds generally absorb at ~250 – 270 nm, which means that molecules such as oxidized !-mercaptoethanol or dithiothreitol will interfere with some measurements of proteins. In addition, nearly all molecules absorb light below 210 nm. Oxygen absorbance increases rapidly below 200 nm, and nitrogen absorbance is significant below 190 nm. Experiments requiring measurements below 200 nm are generally performed in an instrument purged with nitrogen; measurements below 185 nm generally require instruments in which the sample compartment and optical path are located in a vacuum chamber.

http://www.brandtech.com/cuvettegraph.pdf

BRAND UV-Cuvettes

Comparison with Quartz and other Plastic Cuvettes

BRAND UV-Cuvettes are the disposable alternative to quartz cuvettes for applications that require UV-transparency. Unlike Polystyrene (PS) and Polymethyl methacrylate (PMMA or "acrylic") cuvettes, BRAND UV-Cuvettes are transparent down to 220 nm, so they are suited to molecular biology applications, such as A260/280 purity determinations and other analyses in the UV wavelength range.

Besides their UV-transparency, this proprietary plastic is also more resistant to chemical attack than PS or PMMA, and so may bring disposability to applications in which disposable cuvettes were not previously an option because of limited compatibility.

Benefits of disposability

Disposable cuvettes have many advantages over quartz. Since quartz cuvettes are so expensive, typically costing hundreds of dollars, UV-Cuvettes costing much less than a dollar each are economical.

They eliminate the risk of sample carryover, so they can enhance the reliability of analytical results. They eliminate time-wasting washing of cuvettes; taking 5 minutes to wash and dry a cuvette costs more than the price of a UV-Cuvette, even when the work is done at $10 an hour by a student. Furthermore, the one-time use eliminates the risk of scratching or breaking expensive quartz cuvettes. Finally, in molecular biology applications, the availability of individually wrapped UV-Cuvettes, free of DNA, DNase and RNase, provides superior protection for your samples that is not available with reusable quartz cuvettes.

When should you use quartz cuvettes?

No plastic is as clear as quartz, as indicated in the transmission curves, below. In certain applications–such as an extremely dilute sample where the utmost in sensitivity is essential–quartz may be the only option, and you'll have to sacrifice the advantages of UV-Cuvettes. With typical samples, however, including DNA and RNA, just use the UV-Cuvette as your "blank" or standard, and the spectrophotometer will adjust for the difference in absorbance between quartz and our UV-plastic. With our free sample packs, you can give the BRAND UV-Cuvettes a try at no cost, and confirm for yourself.

Does anyone know if there are glass disposable square or rectangular four-sided cuvettes? Have looked at several manufacturers without any luck...

Thanks!

Are the cuvettes you use are made of polycarbonate (Lexan)? Cuvettes made of polycarbonates are clear and fairly resistance to UV light. I think they should be better than others.