software for interactive curve resolution using simplisma
DESCRIPTION
Software for Interactive Curve Resolution using SIMPLISMA. Andrey Bogomolov , Michel Hachey, and Antony Williams. SIMPLISMA is…. SIMPL e-to-Use Intuitive I nteractive Operator is involved in the process S elf-modeling No prior information is required M ixture A nalysis. Willem Windig. - PowerPoint PPT PresentationTRANSCRIPT
Spectroscopy • Chromatography • PhysChem • Naming • Drawing and Databasing • Enterprise Solutions
Software for Interactive Curve Resolution
using SIMPLISMA
Andrey Bogomolov, Michel Hachey, and Antony Williams
Spectroscopy • Chromatography • PhysChem • Naming • Drawing and Databasing • Enterprise Solutions
SIMPLISMA is…
SIMPLe-to-Use• Intuitive
Interactive• Operator is involved in the process
Self-modeling• No prior information is required
Mixture Analysis
Spectroscopy • Chromatography • PhysChem • Naming • Drawing and Databasing • Enterprise Solutions
Willem Windig
SIMPLISMA Reference:
[1] W. Windig and J. Guilment, Anal. Chem. 65 (1991), 1425.
Spectroscopy • Chromatography • PhysChem • Naming • Drawing and Databasing • Enterprise Solutions
SIMPLISMA is a Multivariate Curve Resolution Algorithm
Extract pure component spectra from a series of spectroscopic observations of a mixture while the component concentrations vary
Obtain component concentration profiles for processes evolving in time
Detect the number of mixture components
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General Curve Resolution Problem
assumptions
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Curve Resolution and PCA
rRaw Data
Reproduced Data
Errors
+
c n C-Profiles
Spe
ctraCR
rRaw Data
Reproduced Data
Errors
+
c n Loadings
Sco
resPCA
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Practical Applications
Qualitative characterization of unknown mixtures
Interactive process monitoring Studying chemical reactions’ kinetics
and mechanisms Obtaining equilibrium constants Resolving co-eluting signals in
hyphenated chromatography (HPLC/DAD)
Quantitative analysis (calibration is required)
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Self-Modeling Curve Resolution Algorithms
Evolving Factor Analysis (EFA) Window/Subwindow Factor Analysis
(WFA/SFA) Iterative Target Transformation Factor
Analysis (ITTFA) Rank Annihilation Factor Analysis
(RAFA) Direct Exponential Curve Resolution
Algorithm (DECRA) by W. Windig and more…
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Self-Modeling Basic Steps (Factor-Based Methods)
Deducing the number of components (PCA)
Obtaining initial curve estimates
Iterative improvement using system-specific constraints
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SIMPLISMA is a Purity-Based Approach
A pure variable represents the component concentration profile
Find a pure variable for each component
Solve for the component spectra by means of regression
How to find pure variables?
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Purity Function
Purity Function
Mean
Standard Deviation
c
ijijcj d
1
21
j c iji
c
d11
j
jjp 1
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Purity-Corrected Standard Deviation
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Overestimated Purity Problem
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Overestimated Purity Problem
Purity tends to the infinity when the mean approaches zero
Offset serves to compensate for this effect
Offset is usually defined as % of the mean
j
jjp
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Deducing the Number of Components
Shape of Residuals Shape of the Resolved Curves Shape of Purity and Purity-Corrected
Standard Deviation Spectra TSI vs LSQ plot Cumulative %Variance IND Function
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SIMPLISMA Result
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SIMPLISMA with 2nd Derivative
The algorithm assumes that each component has pure variable
Often, in real-world mixtures this requirement is not met
Inverted 2nd derivative may help!
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Live Data Example
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Advantages of SIMPLISMA
Interactive: unlike black-box algorithms, lets a human interfere
Intuitive: spectrum-like curves are easily interpreted by spectroscopists
Fast: does not perform time-consuming iterative improvements
Flexible: does not use prior assumptions about spectral and curve shapes
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Limitations and Workarounds
Real purity is unknown => assess purity by other algorithms No variance—no component => more experiments to make it vary Too complex data => try to split
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CONCLUSION
SIMPLISMA is a curve resolution program designed for use by spectroscopic experts
Commercial implementation has been transformed into a chemical software interface
Therefore, the hurdles to widespread usage have been overcome!
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Acknowledgments
Willem Windig for the invention Eastman Kodak for licensing the
SIMPLISMA algorithm Yuri Zhukov and Alexey Pastutsan,
the ACD/Labs programmers Antony Williams and Michel Hachey,
colleagues and co-authors