How do you mix solutions in cuvettes - (Apr/18/2007 )

Dear All,

I have to add solutions to cuvettes to perform salicylate determinations and immediately spec at T0 and then again at twenty mins.
My question is what is the best way to mix the solution in these cuvettes?
I have tried pipetting up and down and flicking.

I also tried to add a coloured solution instead of the sample (eosin) and it mixes immediately I add the NADH. Is this good enough? or is more mixing required?

Thank you

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Use parafilm, take small square and pull tight over top of cuvette hold with thumb and invert to mix...

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similar to beccaf22, i place parafilm on top without stretching, place my thumb completely and firmly over the top and index finger on bottom and mix by repeated inversion.

you can also purchase a mixing "plunger" to which you put your enzyme or substrate and, with the cuvette in the spectrophotometer, insert and push down and pull up a few times to mix.

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Thanks for the answers, I did think of some sort of covering, and need to do it without introducing bubbles.
The plunger sounds like a good idea and I'd like to look into that. My problem is that I have 613 of these determinations to do and my spec takes 6 samples at a time, so I wanted to automate it as much as possible.

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ur gonna have to shake it slowly to avoid air bubbles, but well it will take time... so just be patient

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I have done a kinetic assay in cuvettes and have had exactly the same problem as you. What I do is to use the Gilson pipette (P200) that I add my final aliqout with (substrate for reaction). If you add and mix carefully you cause no bubbles. On the odd occasion that you introduce a bubble into the cuvette, use a plastic disposable spatula to "pop" the bubble. This method has worked for me..... but timing is all important. My time point 0 is fairly flexible in that we add enough co-factors for the specific enzyme assay to be linear for 2-3 minutes.

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