[RASMB] s20w calculation

[John Sumida]

Dear RASMB

 

Wondering about the s020w calculation in SEDNTERP 

 

For one of our polymer micelles with which we've been working, a SEDANAL
analysis returns an s20w value (not corrected for concentration) of 17.3.

 

If I use equation 19 in cited in the SEDNTERP documentation, from the s20w
value=17.3, I calculate s* = 16.4s. 

Phsyical parameters used: 

1.     experiment temp=20oC, 

2.     vbar=0.8312 (measured by densitometry at 20oC)

3.     density of solution 1.00506 gms/cm3 (measured)

4.     viscosity 0.010281 (measured)

5.     Assuming viscosity of water to be 0.01002, and the density to be
0.998234

 

However if I use the Experiment page in the SEDNTERP and enter value of s*
calculated above, then s20w returned is 27.8 which is much higher than the
value returned from SEDANAL.  In fact in order to get SEDNTERP to return a
value of 17.3s, I have to decrease S* to be 2.91s.

 

In SEDFIT, if I input 16.4s, calculated from Equation 19 in the SEDNTERP
documentation, and input the same physical parameter listed above, I get
17.4s in agreement with the SEDANAL result.

 

I think in both SEDNTERP and SEDFIT, the same equation is used to correct s*
to s20w, so I'm not clear what I'm missing.

 

Any suggestions and comments are welcome and thank you, in advance, for
taking the time to consider my question.

 

Best regards,

 

John Sumida

 <http://depts.washington.edu/cidb4bio/index.shtml> Analytical Biopharmacy
Core Facility

University of Washington

 <http://www.moles.washington.edu/> Molecular Engineering & Sciences
Institute, G22

3946 West Stevens Way NE

Seattle WA 98195-1653

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://list.rasmb.org/pipermail/rasmb-rasmb.org/attachments/20130808/9635d56c/attachment.htm>