[RASMB] Reproducibility in densitometry measurement

[HGSR (Holger Martin Strauss)]

Hi John,

We try to go as high as possible in concentration, since the vbar is in the density difference between solution and solvent, so we try to make this as large as possible. We have gotten "reasonable" (not to say accurate) values down to 0.5 mg/mL with the DMA5000, but it is really pain. Also, the concentration error becomes more significant at small solute/solvent density differences.

I should add, that our results were still getting better after months of regular/obsessive (well...) use of the instrument. Getting the knack of it wasn't easy nor quick.

Best of luck, Holger

From: John Sumida [mailto:jpsumida at gmail.com]
Sent: 30 September 2014 18:06
To: HGSR (Holger Martin Strauss); rasmb at list.rasmb.org
Subject: RE: [RASMB] Reproducibility in densitometry measurement

Dear Holger,

Thank you for your detailed comments.  Our experience with degassing the sample is consistent with yours: does not appear to make much of a difference.  We have not tried removing the syringe during measurement - Anton Paar rep recommended that we leave it in the plug during the sample measurement.  We will try removing the syringe and see if that helps.

What concentration range to you normally use for your measurments?

Thank you for taking the time to consider my question.

Best regards,
John Sumida.


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