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Greetings RASMB:<br><br>
The scattering increases as the fourth power of the inverse
wavelength. Years ago Aviv's spectrophotometer had a function that
would fit the baselines before and after an absorbance peak to subtract
the scattering portion. <br><br>
However, I cringe at the idea of making analytical measurements of
particles via absorbance. Absorbance of a photo can happen only
once. Scattering can happen more than once, sending a photon back into
the detector's view. The detectors of different instruments view
different collection angles of the sample, so the amount of scattered
light is going to vary depending on the instrument design.
Reflections of scattered light off the surroundings can send photons back
onto the detector. In one custom instrument Aviv mounted the detector on
a rail, and apertures were mounted on both the sample's exit and
detector's entrance, to control the light collection angle. And of
course the size of the particle affects the amount of light
scattering.<br><br>
Measure scattering with absorbance with both eyes and mind open, because
the instrument is not being used as intended.<br><br>
Glen<br><br>
<br>
At 09:44 AM 3/5/2010, Steve Harding wrote:<br>
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<font size=2>Dear Sabine<br>
Simple turbidity measurements (making sure you are <u>away</u> from
absorption maxima) using a good quality spectrophotometer <u>may
</u>suffice for the sort of information you are after - particle
concentration, although stricvtly speaking it is not a hydrodynamic
method.. This is is the usual method for measuring concentrations
(particles per ml) of very large assemblies such as spores and I think it
works for smaller assemblies that are not too dilute..<br>
Victor Bloomfield's group did quite a bit on the turbidity of phages in
the late 70's and gave the relevant formulae (you may need the
approx mol. wt value) - if you look up Bahls and Bloomfield (and
not Victor's QLS papers) that should give you a lead!<br>
All best<br>
Steve Harding<br>
</font> <br>
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http://www.nottingham.ac.uk/ncmh</a><br>
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<font size=2>> Dear all,<br>
><br>
> we are trying to obtain the concentration of bacteriophages in
a<br>
> solution, concentration meaning the number of particles per ml.
The<br>
> solution is supposed to be monodisperse and the MW is (roughly)
known<br>
> but could be determined exactly. Is the any idea of how to do
this<br>
> with a hydrodynamic method (staining is difficult to compare
between<br>
> phage mutants and counting infected cells is tedious). I`ve got
the<br>
> "feeling" that one could use the number-averaged MW, but
maybe this is<br>
> totally wrong.<br>
><br>
> Thank you for any hints, literature is also welcome.<br>
><br>
> Cheers,<br>
><br>
> Sabine<br>
><br>
><br>
><br>
><br>
> Sabine Kaltofen<br>
> PhD student<br>
><br>
> Universität Potsdam<br>
> Department of Physical Biochemistry<br>
> Institute of Biochemistry and Biology<br>
> Karl-Liebknecht-Str. 24-25, Haus 25, Raum B/0.05<br>
> D-14476 Potsdam-Golm<br>
> Telefon: +49-(331)-977-5245<br>
> Email: kaltofen@uni-potsdam.de<br>
><br>
><br>
</font><br>
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<br>
Glen Ramsay, Ph.D.<br>
Chief Scientist<br>
Aviv Biomedical, Inc.<br>
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(732) 370-1300, Ext. 25<br>
(732) 370-1303, FAX<br>
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