Hi,

We have experienced similar problems and did some analysis. Here are the results:

Test of several Imidazole solutions for absorbance at 280 nm. The solutions have been prepared from the powders purchased from different suppliers.


Here is the data:

Wavelength

2 M Stock solution
(unbuffered in MQ water)

250 mM solution
 in MQ water

VWR/PROLABO

260 nm

1.249

0.141

VWR/PROLABO

280 nm

1.628

0.192

VWR/PROLABO

320 nm

1.259

0.139




VWR/MERK

260 nm

0.060

0.010

VWR/MERK

280 nm

0.049

0.002

VWR/MERK

320 nm

0.028

0.002




Opened Sigma

260 nm

1.386

0.158

Opened Sigma

280 nm

1.545

0.178

Opened Sigma

320 nm

0.931

0.104




Unopened Sigma

260 nm

2.277

0.276

Unopened Sigma

280 nm

2.734

0.327

Unopened Sigma

320 nm

1.258

0.147



Hope it would help to other people as well ,

Kostya

-- 
Konstantin (Kostya) Kogan
Postdoc fellow
Adrian Goldman's Lab
Division of Biochemistry and Biotechnology
Department of Biosciences
Faculty of Biological and Enviromental Sciences
University of Helsinki
Viikinkaari 5D, Room 3036b
POB 56, 00014
Helsinki, Finland
Mobile: +358-(0)45-8994342
Office: +358-(0)9-191-58907


On 22/08/2013 4:03 AM, John Newitt wrote:
[log in to unmask]" type="cite">
Yes, I think that's the one we use now. I believe it is the current branding of the Fluka imidazole that we always ordered. Definitely lower UV absorbance. We also prefer Roche high purity DTT for the same reason.

John

Sent from my iPad

On Aug 21, 2013, at 11:04 AM, Jan <[log in to unmask]> wrote:

Hi Bernhard,
this one works for us:
Sigma BioUltra imidazole, >99.5% by GC, 56749

Cheers,
Jan
--
Jan Abendroth
Emerald BioStructures
Seattle / Bainbridge Island WA, USA
home: Jan.Abendroth_at_gmail.com
work: JAbendroth_at_embios.com

On Aug 21, 2013, at 7:33 AM, Bernhard Rupp <[log in to unmask]> wrote:

Hi Fellows,
 
could someone please point me towards the source of a known high purity imidazole
with low absorbance at 280 nm? I am facing the problem of detecting a low absorption protein
in high imidazole background after IMAC gradient elution. In the UV spectra of the
2 imidazoles I checked there is some contaminant that absorbs at 280…  
 
Thx, BR
 
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Bernhard Rupp
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Innsbruck Medical University
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A 6020 Innsbruck – Austria
+43 (676) 571-0536
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