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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: Liverspots on November 22, 2012, 08:59:45 AM

Title: Literature values for extinction coefficients?
Post by: Liverspots on November 22, 2012, 08:59:45 AM
I've been struggling to understand extinction coefficients, ε, for a thermal lens calorimetry experiment I am working on.

I've used my lab data to calculate ε using the formula ε = (ΔBeam Intensity/Initial Beam Intensity)/(E*b*c*2.303). That seems to be fine. But I want to a % error comparison with the values I am producing and I'm having trouble locating a good source (specifically online, but print will work in a few more days).

To be specific I need to located ε for:
Indophenol in methanol
Trypan blue in methanol
Bromophenol blue in acetone
Bromophenol blue in water
Bromophenol blue in methanol

Thank you for any advice you are able to share.
Title: Re: Literature values for extinction coefficients?
Post by: Arkcon on November 24, 2012, 01:07:03 PM
You could try Googling for your terms. Several years ago, there was a webpage, made by someone, that had the excitation and emission max (fluorescence) for a number of biological stains and similar dyes.  But I don't know of comprehensive, well-maintained lists.  This webpage was just someone with some knowledge and some free time on their hands to code it all in a web page.  There may be better things available, but there may also be no interest in hosting such data.
Title: Re: Literature values for extinction coefficients?
Post by: MOTOBALL on November 25, 2012, 11:51:49 AM
                                                λmax           log ε

Indophenol (MeOH)                     262            4.19
                                                 314            3.97
                                                 503            3.93

Bromophenol Blue (water)           440            3.48
                                                 600            4.82

Ref. CRC Handbook of Chemistry & Physics, 59th Ed. 1978-9. (only those solvents)

I'm working on Trypan Blue.

Title: Re: Literature values for extinction coefficients?
Post by: Liverspots on November 25, 2012, 01:41:05 PM
Thank you for what you've been able to find. Does the extinction coefficient of a solution vary by what solvent is used? I suspect it does but I am not 100% sure.
Title: Re: Literature values for extinction coefficients?
Post by: Babcock_Hall on November 25, 2012, 05:08:55 PM
Sometimes only the λmax shifts with a change in solvent, but I believe that there are cases where both ε and λmax shift.  You might look up bathochromic or hypsochromic shifts.
Title: Re: Literature values for extinction coefficients?
Post by: Arkcon on January 18, 2013, 09:56:52 PM
Digging through some old bookmarks, I found one of the pages I mentioned.  Click on the Dyes tab and see if you can find the sort of information you might need.  http://stainsfile.info/StainsFile/jindex.html
Title: Re: Literature values for extinction coefficients?
Post by: Time_sama on July 09, 2020, 01:42:07 PM
Quote from: MOTOBALL on November 25, 2012, 11:51:49 AM
                                                λmax           log ε

Indophenol (MeOH)                     262            4.19
                                                 314            3.97
                                                 503            3.93

Bromophenol Blue (water)           440            3.48
                                                 600            4.82

Ref. CRC Handbook of Chemistry & Physics, 59th Ed. 1978-9. (only those solvents)

I'm working on Trypan Blue.

Hi, sorry for the very late answer, but I needed this data in the research and it seemed strange for me. Couldn'd find these in CRC (my bad), so I checked it myself.
For BPB the ε in water at 438 nm is 24429 ±1100, at 591 nm is 86317 ±5983
The range of concentrations from 10-5 to 10-6 at pH 2 and 11 respectively
It seems for me that at CRC the ε for BPB is given for MeOH, as I received
For BPB the ε in MeOH at 424 nm is 3501±1133, at 596 nm is 95959 ±2257
all ε are L mol-1 cm-1
The plots are in the attachment
Kind regards