April 13, 2021, 03:42:31 AM
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Topic: Molar absorptivity  (Read 162 times)

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Offline Titration_Man

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Molar absorptivity
« on: March 26, 2021, 05:37:03 PM »
I'm looking to confirm if whether or not this conversion is correct. I found this conversion from E1% to ε from this site here https://www.chemeurope.com/en/encyclopedia/Molar_absorptivity.html and it's the only reference I've been able to find. It states the ε units are L mol-1cm-1, while E1% L g-1cm-1. It would make sense then if you know your E1% and molar mass of your analyte, to simply multiply by X g/mol (x being the mass) to convert from E1% to ε. However, the conversion provided by the link above has ε =(E1%* molecular weight)/10. What's the point of dividing by 10?

For instance, I have the E1%,1 cm, light-absorption maximum, value for retinol listed as 1832 (325 nm) which I found in the Specification and Criteria for Biochemical Compounds: Third Edition, Page 78 - which I got for free here: https://www.nap.edu/read/21491/chapter/4#78 Retinol's MW is 286.45 g/mol. Therefore ε = (1832 L g-1cm-1 * 286.45 g mol-1) = 524,776.4 L mol-1cm-1. Again, why divide the equation by 10 as listed above?

Offline Borek

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Re: Molar absorptivity
« Reply #1 on: March 27, 2021, 05:20:45 AM »
Without even trying to dig into units/numbers you have listed, 10 suggests combination of 1000 (like mL in L) and 100 (like in %). Perhaps this is a combined conversion factor?
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Offline mjc123

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Re: Molar absorptivity
« Reply #2 on: March 27, 2021, 12:16:17 PM »
Because a 1% solution is 10 g/L.

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