[RASMB] XLI absorbance problem

[Igor Perevyazko]

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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