[RASMB] XLI absorbance problem

[Igor Perevyazko]

Dear Andrew, dear Boris

Thank you very much for your suggestions!
Well, the interference optics works fine on the same cell and as can be
seen by eye the magnetic dot on the stripped ring seems to be ok. At the
moment I have only tried the same cell and monochromator on the working XLI
Regarding the Borris's points:
I have performed the intensity scan with an empty cell in the hole and the
radial position is in the normal range (left on 5.8 and right on 7.15), so
the radial calibration seems to be ok. The thing is that as you can see on
graph 2, I have also checked the intensity of  reference (benzene) and the
sample sector filled with dye solution (Pyrene) and it has practically the
same intensity level as if I scan an empty cell.  As I see it, if there was
a delay problem the intensity of a cell filled with a solution must be
close to 0 then, if I understand your concern correctly. I have also
attached the radial intensity scan for a cell (no windows).

Best regards
Igor

On Fri, Feb 20, 2015 at 6:31 PM, Borries Demeler <
demeler at biochem.uthscsa.edu> wrote:

> Dear Igor,
> I agree with Andrew, this looks like a timing problem, obviously when
> you intensity scan an empty hole it doesn't have this problem (no septum,
> cell components in the light path) so the timing being a little bit off
> still lets it hit the hole, just not a 2.5 degree channel. Can you still
> perform an intensity scan when you put an empty cell in the hole? I am
> not sure what the radial position was. If the radial calibration is off
> you may not be at the position you think you are, so radially scan an empty
> cell or the counterbalance and make sure the edges are at reasonable
> positions.
>
> -b.
>
> On Fri, Feb 20, 2015 at 04:20:53PM +0300, Igor Perevyazko wrote:
> > Dear RASMB members,
> >
> >
> >
> > We are having a problem with absorbance optics on XLI centrifuge(XLI_1 on
> > the images attached). Hopefully you can suggest something that will
> > help. The problem is that optical density of any samples (which
> definitely
> > absorb, including for example BSA (c = 4mg/mL) or pyrene dye (c = 10然 ))
> > recorded by the AUC is within the zero  level. Nevertheless, at much
> higher
> > concentrations (approximately 10 -20 times higher) the optical density
> > reaches some level of absorbance (~0.1-0.2 OD). The same solutions
> checked
> > by normal UV-Vis spectrophotometer and on another XLI centrifuge (XLI_2),
> > have adequate values of the absorbance level. We have as well checked our
> > monochromator   on  XLI_2 and it was working ok. Recorded lamp
> intensities
> > (air to air) at 230 nm and 530 nm are at the normal level. If we perform
> > the absorbance scan of a sample (for example Pyrene dye at c = 10然)  in
> > the intensity mode, we received the same level of intensities for both
> > reference and sample chamber! The corresponding comparison of the
> > intensities is shown on the image attached. Any of your suggestions about
> > the possible problem and/or the solution will be highly appreciated.
> >
> >
> > Best regards
> >
> > Igor Perevyazko
> >
> >
> > PhD Igor Perevyazko
> > Physics Department, Polymer Physics
> > St.Petersburg State University
> > Ul. Ulyanovskaya 1, Petrodvorets
> > St.Petersburg, Russia, 198504
> > Tel.: (812)4284382
> > Fax.: (812)4287240
>
>
>
> > _______________________________________________
> > RASMB mailing list
> > RASMB at list.rasmb.org
> > http://list.rasmb.org/listinfo.cgi/rasmb-rasmb.org
>
>
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