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Net Analyte Signal Based Multivariate Calibration Methods

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Net Analyte Signal Based Multivariate Calibration Methods By: Bahram Hemmateenejad Medicinal & Natural Products Chemistry Research Center, Shiraz University of ... – PowerPoint PPT presentation

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Title: Net Analyte Signal Based Multivariate Calibration Methods


1
Net Analyte Signal BasedMultivariate
Calibration Methods
  • By
  • Bahram Hemmateenejad
  • Medicinal Natural Products Chemistry Research
    Center, Shiraz University of Medical Science

2
Multivariate Calibration
  • CLS A C S
  • ILS c A S
  • PCR A T P, c T s
  • PLS A T P, C Q U Q T b

3
Main Problems
  • Definition of figures of merit
  • Optimization of conditions
  • Optimum number of factors

4
Figure of merit
  • Sensitivity
  • Selectivity
  • Detection Limit
  • Univariate Calibration

5
Optimization of conditions
  • Effect of pH
  • Effect of Temperature
  • Effect of Ionic Strength
  • Effect of Concentration

6
Optimum number of factors
Cross Validation External Validation Minimum
PRESS F-Ratio Over-fitting Under-Fitting
7
Net Analyte Signal(NAS)
  • A. Lorber, Anal. Chem. 58 (1986) 1167
  • The part of mixture spectrum that is useful for
    model building
  • NAS is unique for the analyte of interest
  • NAS is a part of mixture spectrum which is
    orthogonal to the spectrum of all existing
    components except analyte
  • A part of mixture spectra which is directly
    related to the concentration of analyte

8
Net analyte signal, references
  • 1986 Proposed by Lorber.
  • Spectra of pure compounds available (CLS model).
  • 1997-2000 Extensions.
  • Inverse calibration (Lorber,Faber,Kowalski)
  • Figures of merit (sensitivity, selectivity,
    limit of detection) (Faber)
  • 1998-2002 Applications, Software.
  • Outlier detection. (Faber, Xu, Ferre)
  • Biomedical Pharmaceutical. (Goicoechea,
    Skibsted)
  • Spectral preprocessing. (Faber, Brown, Wentzell)
  • Wavelength selection. (Goicoechea, Xu)
  • Preprocessing and wavelength selection (Skibsted,
    Boelens)

9
M1
M2
M3
y
x
2x
3x
3y
M3
2y
M2
y
M1
x
10
  • R (ixj) matrix of mixture spectra
  • Rk (ixj) matrix of analyte k spectra
  • R-k (ixj) matrix of background (other analytes
    interferences
  • R C S
  • Rk sk ck
  • R Rk R-k
  • F R F Rk F R-k, F R-k 0
  • F R F Rk R F sk ck sk ck

11
  • F I R-k R-k
  • R (I R-k R-k)R R - R-k R-k R
  • (I R-k R-k)R-k 0
  • Key Step R-k
  • Rank Annihilation Factor Analysis
  • (RAFA)

12
  • CLS approach
  • Rk sk ck
  • R-k R Rk
  • ILS approach
  • R-k R - ? r ck
  • r is a linear combination of the rows of R
  • ck R R-1 ck
  • ? 1/ rT R ck

13
  • Another approach
  • R-k I ck(ckT ck)-1 ckTR
  • Other approaches
  • Xu Schechter Anal. Chem. 69 (1997) 3722
  • Faber Anal. Chem. 70(1998) 5108

14
Review of NAS calculation
  • Determining No. of analytes (p)
  • Preparing mixture standard solutions (j)
  • Recording absorbance spectra of solutions at (i)
    sensors (R matrix)
  • Recording absorbance spectrum of unknown (run
    vector)
  • Calculation of R-k

15
  • Calculation of calibration NAS
  • R (I R-k R-k)R
  • Calculation of the NAS for unknown
  • run (I R-k R-k)run
  • Calculation of the pure NAS
  • sk (I R-k R-k)sk

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Effect of added noise
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NAS-Multivariate calibration
  • In some case,
  • Nonlinearity
  • Interaction between components
  • Other source of variables
  • The rank of NAS will become greater than 1
  • Simple NAS method dose not give perfect results
  • MLR, PCR, PLS and help to enhance the results
    of NAS calculation

66
  • R is used as input for multivariate models
  • R c s
    MLR
  • R T P c T b
    PCR
  • R T P c u q u T b PLS
  • R can be used as input for ANN

  • In Progress

67
Figure of merits
68
  • Sensitivity ri / ci or s
  • Selectivity ri / ri or s /
    s
  • LOD 3Sc / m, 3 ? bk /
    m
  • LOQ 10Sc / m, 10 ? bk / m

69
Applications
  • Wavelength region selection

Net Analyte Signal Regression Plot (NASRP)
70
  • Error Indicator (EI)
  • Goicoechea and Olivieri, Analyst 124 (1999) 725
  • EI s2 1(N2s2) / 4 r )0.5 / r
  • s standard deviation of the best fitted line
  • N Number of point in the best fitted line

71
  • Temperature insensitive determination of proteins
    in electrolyte solutions
  • Anal. Chem. 72 (2000) 4985
  • Determination of Tetracycline in blood serum
  • Anal. Chem. 71 (1999) 4361.
  • Determination of drugs in pharmaceutics
  • Determination of drugs in serum
  • Determination of sorbic and benzoic acids in
    fruit juices

72
Multivariate Standard Addition Method (MSAM)
  • ck cu cs
  • R R-k Rk
  • R-k R - ? r ck R - ? r (cu cs)
  • R-k I ck(ckT ck)-1 ckTR

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  • Thanks for you attention
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