The lab I started working in has a spectrophotometer with cuvettes. The cuvettes need to be inspected and cleaned regularly. The senior people in the lab are in disagreement as to the correct procedure for cleaning them. Some recommend soap and a bristle brush with running water, others just suggest leaving them to soak in an ethanol solution.

The question is twofold;

a) Is there any risk that the brush will scratch the glass?

b) Is there any advantage to the soap method? If not, I am wasting an hour of my boss' time and money.

  • $\begingroup$ I would think the thing to do is to consult the manufacturer of the cuvettes... $\endgroup$ – Zhe Sep 26 '17 at 14:33
  • $\begingroup$ Not sure what kind of cuvettes you are using, nor what types of solutions you are using. I'd agree with andselisk. No abrasives also meaning no brush which can hold grit. If you're using the square UV/Vis cuvettes with a thin quartz window then I'd certainly stay away from a brush. My thought if the cuvettes are really cruddy, then I'd soak them in a acidic chromate cleaning solution. $\endgroup$ – MaxW Sep 26 '17 at 15:01

I always managed to wash out the remaining solution with the corresponding solvent a couple of times, subsequently rinsing with acetone/isopropyl alcohol and leave it dry on air for a few minutes. The method of spectrophotometry requires that you are using homogeneous solution anyway, so there shouldn't be any precipitation/deposition, otherwise you cannot interpret the data with Beer-Lambert law.

Also, don't soak cells in KOH-bath or similar alkaline media. And I'm always strongly against abrasives, especially when it comes to cleaning optics. Even quartz cuvettes can be occasionally damaged with the brush pick. Disposable PS-cells can be easily scratched. Plus, there is a little risk of hydraulic pressure knocking out the cuvette's bottom (like it happens with test tubes when cleaned too vigorously). Leave mechanical cleaning for the professors of mechanics *.

*From a story published in The Oxford Book of Scientific Anecdotes:

Victor Moritz Goldschmidt, a distinguished geochemist, was reputed to have carried a capsule of potassium cyanide when he was planning his escape from Nazi Germany. When a friend in the engineering department of the university expressed interest, Goldschmidt was supposed to have replied that cyanide was for professors of chemistry; his friend, a professor of mechanics, would have to carry a rope.

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