Chem 287_Chapter 19

Chem 287_Chapter 19 - Lectures: Classical Methods of...

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Lectures: Classical Methods of Chemical Analysis 1 Spectrophotometry Chapter 19 To be covered: 1) Instrumentation Problems: 3,4,9,11 1) Instrumentation 2) Multi-component Quantification 3) Luminescence Spectrophotometry Spectrophotometry is the study of energy transitions. C C A L where E j E i where: C = Collisions A = Absorption L = Luminescence or emission Absorbance and Emission of EM radiation are quantitative.
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Lectures: Classical Methods of Chemical Analysis 2 Beer-Lambert Law Real measurements have finite thickness: dx P the light traveling through the sample will be - dP /P = c dx Po P 0 b P Po b 0 Evaluating the integral ln ( Po / P) = cb log ( Po / P) = ( / 2.303) cb A = log ( Po / P) = abc or = log T = bc a = molar absorption coeff. = extinction coeff. Errors in Spectroscopy Common error source in spectroscopy is due to stray light and detector noise. The log ratio relationship of the absorbance is non-linear with stray light and noise. Log((I 0 +N+I stray ) /(I +N+I stray ))~ abc Straylight (fraction I o ) Cheap =.1 Lab = 0.005 ce Ideal Research =0.0001 Absorbanc C 10% Stray light
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Lectures: Classical Methods of Chemical Analysis 3
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This note was uploaded on 07/15/2011 for the course CHEM 287 taught by Professor Burns during the Fall '08 term at McGill.

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Chem 287_Chapter 19 - Lectures: Classical Methods of...

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