Dr. Ottorino-Luca Pantani <ottorino-luca.pantani <at> unifi.it> writes:
>
> In a lab experiment I have to mix three solutions to get different
> concentrations of various molecules in a cuvette
>
> I've used R to calculate the necessary µliters for each of the level of
> the experiment and I must confess that it is more useful and easier to
> achieve the results than using spreadsheets.
>
> But there's a problem.
>
> Imagine that for a particular cuvette (I have 112 different cuvettes !!)
> you have to mix the following volumes of solution A, B, and C respectively.
>
> c(1803.02, 193.51, 3.47)
>
> Each solution is to be taken with 3 different pipettes (5000, 250 and 10
> µL Volume max) and each of those delivers volumes in steps of 50 µL, 5
> µL or 1µL, respectively
> Since the above values would eventually become
>
> c(1800, 195, 3)
>
> it is then necessary to recalculate all the final concentrations
> of A, B and C, because the volumes are changed.
A first guess would be
a = c(1803.02, 193.51, 3.47)
round(a / 5)*5
which gives
1805 195 5
This is not exactly what you want, but it shows that the problem is a bit
ill-defined. In the example you gave, why do you want 1800, and not 1805, which
is possible with the pipettes? I assume that you laboratory experience is
working in the background, telling you to stop pipetmanning when you are close
to the result in some "percentage" feeling.
Dieter
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