[RASMB] XLI absorbance problem

[Andrew Leech]

Hi Igor,

It doesn't look like you are scanning the cell at all, but an empty
hole. I think this can happen if you have the delay times really
badly out. Are the interference optics working ok on the same cell?
Have you tried scanning the counterbalance in the highest number hole?
Has the magnetic dot on the striped ring under the rotor been damaged?
(Have you tried the same cell/rotor combination on the working XLI?)
Some things to try anyway!

All the best,

Andrew

On 20/02/2015 13:20, 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 = 10µM )) 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 = 10µM)  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
>
>
>
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>

-- 
Dr Andrew Leech                   *  Laboratory Head
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