[RASMB] Nanoparticle absorbance question

John Philo jphilo at mailway.com
Wed Jun 13 12:28:23 PDT 2012


Debby,
 
Not sure any of these explain negative readings, but here are some things to
consider:
 
(1) Did you remember to rotate the lever on the monochromator to filter out
the stray light below 400 nm? Either way, 
you may want to take a scan in intensity mode to see whether you really have
enough light going through to make a reasonable measurement. The lamp
outputs very little light in the visible compared to the UV.
 
(2) Could the wavelength calibration be way off in the visible region?
 
(3) Is it possible your particles sediment so fast they had simply already
pelleted by the time you could take a measurement?
 
 
John

  _____  

From: rasmb-bounces at rasmb.bbri.org [mailto:rasmb-bounces at rasmb.bbri.org] On
Behalf Of Deborah Pheasant
Sent: Wednesday, June 13, 2012 12:10 PM
To: rasmb at server1.bbri.org
Subject: [RASMB] Nanoparticle absorbance question



Hi all,

We had a suspension of nanoparticles (metal oxides) in culture medium with
FBS proteins and it measured 0.5 AU at 530 nm in a UV/VIS spec.  When we put
it into SV centerpieces, it read that it had an A530 of about -0.1 or -0.2.
We are perplexed as to why this should be.  Have you had similar experiences
or do you have an idea about what might be going on?

Thanks very much,

Debby Pheasant

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