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### Topic: spectroscopy absorbances  (Read 215 times)

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#### Jotach

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##### spectroscopy absorbances
« on: December 16, 2020, 04:52:11 AM »
Hi!

Last we tried to find the concentration of Mn in an alloy based on spectroscopy.

Now we found the absorbance relative to the blank from the standard solution (0.24) and the absorbance relative to the blank from the unknown solution (0.26).

We also made a calibration curve based on the standard solution (A(c) = -0,04 + 2350*c )

Now we're wondering how we have to calculate the concentration of the unknown solution, should we use 0.24 or 0.26 or should we use the difference between the two absorbances to make an new relation between A and c?

thanks!

#### chenbeier

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##### Re: spectroscopy absorbances
« Reply #1 on: December 16, 2020, 06:28:45 AM »
How do you made the calibration curve?
What is the concentration of your standard?
According the values of absorbance, the concentration of unknown sample is a little higher as your standard.
If the formula is correct calculate with 0,26 for sample. 0,24 should give your standard concentration.

#### Jotach

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##### Re: spectroscopy absorbances
« Reply #2 on: December 16, 2020, 07:19:35 AM »
The calibration curve is based on different solutions of the standard (4.0E-3 M)

#### Corribus

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##### Re: spectroscopy absorbances
« Reply #3 on: December 16, 2020, 09:31:28 AM »
Why does your blank have lower absorbance than your first few standards?
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman