[RASMB] density meter accuracy/precision

[Jo Butler]

Dear Steve,

If all you want is a solvent density, then you really only need (at 
most) 3 decimal places and the DMA5000 is over the top, since you are 
most unlikely to know the partial specific volume to this precision 
(since the product v-bar*rho will only have the precision of the least 
precise term).
However, if you think that you might ever want to get into the business 
of measuring density increments, and hence being able to calculate 
meaningful apparent partial specific volumes, then all the precision you 
can get in density is wanted, as one is looking at density differences 
between solution and solvent where the solute concentration is likely to 
be only mg/ml (i.e. 10–3), so a precision of 10–6 is by no means too high.

Good luck,

Jo

Stephen Eyles wrote:
> Hi AUCers.
>
> We are contemplating purchasing a densitometer to more accurately 
> determine densities of our buffer solutions for AUC.
> What precision/accuracy is really necessary? I know the de facto 
> standard instrument seems to be the Anton Paar DMA5000 but is this 
> overkill? Aside the significant extra expense, is there a real benefit 
> to 6-decimal place measurement of density or could we do a reasonable 
> job with a hand-held instrument? Weighing known volumes on a balance 
> clearly isn't cutting the mustard!
>
> Thanks for any advice and helpful tips.
>
> Steve
>
> ------------------------------------------------
> Dr Stephen J. Eyles
> University of Massachusetts - Amherst
> Amherst, MA 01003, USA
> eyles at polysci.umass.edu
> Tel: (413) 577-1528
> Fax: (413) 545-0082
> ------------------------------------------------
>
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-- 
Dr P.J.G. Butler,
MRC Laboratory of Molecular Biology,
Hills Road, Cambridge, CB2 0QH, UK.
Tel. +44 (0)1223 402296