glass cuvette cleaning

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glass cuvette cleaning

Post by adihutama » Tue Mar 06, 2012 8:24 am

Dear all,

I know my subsequent question is not really connected with biology, but i guess you people work with it a lot, so you might know.

Our factory is having a new device called bench top turbiditymeter. This instrument use glass cuvette to contain sample. the manual said that the cuvette should periodically washed using acid.
Problem is: which acid is the best for the purpose?
I have browsed around myself and found that some people use acetic acid, sulfuric acid, or nitric acid, of course diluted. They say that you can use alcohol but you shall never use base.

But as i investigate further, and specify my search into glass cuvette. More more and more suggestion direct me to alcohol or even base to be used as cleaning agent.

actually when i check on the producers website, they had specific cuvette cleaning solution, and it only stated alcohol as it main composition.

Which one do you guys think i should go with? Alcohol or acid? If its acid? Which acid should I use?

Are these cleaning agents safe for the cuvette?

Thank you so much for reading and answering

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Post by JackBean » Tue Mar 06, 2012 12:35 pm

I guess that depends on what are you measuring.

Cis or trans? That's what matters.

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Re: glass cuvette cleaning

Post by jonmoulton » Tue Mar 06, 2012 4:50 pm

First a clean glassware story: while an undergrad, I spent a summer working in a state occupational safety lab. My duties included cleaning the glassware used in air quality monitoring gear. These air quality monitors were beltpacks worn by a worker to determine airborne chemical exposure while working and the equipment included a glass impinger, basically a bubbler with a glass frit at the bottom of a tube immersed in liquid and contained in an outer glass tube. Air was drawn through the impinger by a battery-powered pump and airborne chemicals could be caught in the liquid. The liquid was sent back to the lab to be analyzed (GM/MS, ion chromatography, etc.).

These impingers had to be extremely clean, with no organic chemicals on the glass surfaces which might contaminate a sample; a false positive could lead to inappropriately citing a company for illegal chemical exposures. I washed the glassware by suiting up in rubber boots, gloves, face shield and rubber apron and soaking the glass in a mixture of concentrated sulfuric and chromic acids in a fume hood, followed by extensive washing.

** end of the clean glassware story **

You will not need to go to this extent to clean the turbidity meter. You are not measuring chemical compositions, but instead making a physical measurement of particle sizes. Minor chemical contamination is unlikely to perturb the measurement (but see below).

For an occasional thorough cleaning, I'd guess a wash in dilute sulfuric acid (remember to add the acid to the dilution water, not the other way around) followed by extensive repeated rinsing in distilled deionized water would be more than needed to clean the cuvette. The rinsing is critical -- get all the water off the cuvette between rinses and I'd do at least five rinses. Using smaller volumes of rinse water and repeating the rinse is more effective than using larger rinse volumes fewer times. Between most measurements, rinsing with high-proof alcohol followed by several rinses with clean water will likely suffice to keep the data reproducible.

Jack's question is important in determining your protocol: what are you measuring? I answered as though you plan to measure bacterial turbidities, for which some trace contamination on the glassware is unlikely to skew the measurement. If you are measuring chemical aggregates which might be flocculated or disrupted by chemicals in the pipet, more rigorous cleaning might be appropriate to avoid skewing the turbidity data.

You can always try making a standard solution and measuring it several times both before and after cleaning the pipet. That might reveal whether an uncleaned pipet causes a measurable systematic shift in the data.

Good luck with the new instrument!

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