getting rid of rayleigh
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Getting rid of Rayleigh
Åsmund Rinnan
IntroductionFluorescence
Lightsource
Sample
Detector
Excitessample
Emittedfrom sample
IntroductionFluorescence
IntroductionPARAFAC
ijk
F
fkfjfifijk ecbax
1
X is the EEMa are the scoresb are the emissionspectrac are the excitationspectraE is the residuals
Can be seen as an expansion of PCA from two-way data to multi-way data
ij
F
fjfifij eptx
1
=
A
B
C
IntroductionPARAFAC & Fluorescence
IntroductionPARAFAC & Fluorescence
Catechol
Hydroquinone
Introduction”Faking” fluorescence
IntroductionLight scatter
IntroductionLight scatter – The trouble maker
Excita
tion
Emission
2n
d o
rder
Rayle
igh
1st
ord
er
Rayle
igh
Ram
an
IntroductionLight scatter
IntroductionBi-linearity
IntroductionWhy is this a problem?
X
X
ExampleFluorescence & PARAFAC
Getting rid of Rayleigh
•Subtraction of standard
•Cut off and insert missing/ zeros
•Weights•Modeling of Rayleigh
Subtracting a standard
Missing values
Missingvalues
Zeros
Signal/ Data area
Thygesen, Rinnan, Barsberg & Møller
Example
• 18 wood samples• 4 different levels of p-benzoquinone adsorbed in
the fiber cell walls• 30 emission wavelengths x 35 excitation
wavelengths
Thygesen, Rinnan, Barsberg & Møller
WOW!
None Weighted
Non-Negativity Zeros
So, now Rayleigh is finished, right?
• The data presented so far is a bit simple Sugar data
Excitation
Emission 1st o
rder
Ray
leig
h
Weighting - MILES
Emission loadings Excitation loadings
Band of missing values
Using a band of missing valuesHard weights
Emission loadings Excitation loadings
Using a band of missing valuesMILES weights
Emission loadings Excitation loadings
Another method?Why, why, why?
• The Rayleigh scatter width has to be estimated quite accurately
• The band width of missing data should also be correct
• What about an automatic method of removing the Rayleigh scatter, that was not so prone to the estimation of the width of the Rayleigh scatter?
• Modeling the Rayleigh is the answer!
Modeling Rayleigh
• A Gauss-Lorentz curve fitting method
Modeling Rayleigh
Rinnan, Booksh & Bro
Modeling Rayleigh
With constraints even better
Emission loadings Excitation loadings
Rinnan, Booksh & Bro
• Thanks to: Rasmus Bro, Karl Booksh, Lisbeth G Thygesen, Søren Barsberg, Jens K S Møller and Charlotte Andersen
• Thank you for your attention
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