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### Topic: Trying to convert from Abs/min to M/min  (Read 24109 times)

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#### grignardgirl

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##### Trying to convert from Abs/min to M/min
« on: October 17, 2007, 12:22:18 AM »
Hey everyone!  So I'm trying to convert from Absorbance per minute to Molarity per minute.  I know that I am supposed to use A=ebc but I'm not sure how the dimensional analysis works with this.

I'm given: .429 Abs/min and e = 2500 1/M x cm

This is from a Lineburke-weaver plot.  .429 is the Vmax and the Km is .016 M.  Thank you in advance!!

#### ARGOS++

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##### Re: Trying to convert from Abs/min to M/min
« Reply #1 on: October 17, 2007, 12:27:05 PM »

Dear GrignardGirl,

Who is “Lineburke”?, - never heard of him/it, and it seems nobody (Google, Yahoo!, MSN, Alta Vista, etc.) else too!

Abs/min indicates a “Single Wavelength measurement” (SWM) for a Reaction, what seems to be not very wisely!

But let’s do the little “brain acrobatics” anyway:
Abs/min” or more correct ΔAbs/Δt,  like dAbs/dt is a “Reaction Rate”, and if you use the “Special Beer-Lambert Law” (for only a SWM it’s enough) you have to write:
ΔAbs/Δt    ==>   ΔAλ/Δt = Δ(ελ * c * d)/Δt

On the other side and from the definition of ελ
If you set for your case for Aλ = 2500 AU into the “Special Beer-Lambert Law”:
Aλ = ελ * c * d you will result in:

2500 AU = 2500 L mole-1 cm-1  *  c * d

Or with simple words:  ελ is “only” the theoretical Absorbance (value) for a Solution with Concentration = 1.00 Mole/L measured in a 1.00cm Cuvette with the given ελ.

And the final calculation:
2500 AU/min = 1.00 mole/min  ===>  0.429AU/min = mole/min.
(I’m still searching for its real sense.)

Could this be of help to you?

Good Luck!
ARGOS++

P.S.: What should in this case “Vmax” and “Km” tell us?
.