Chemometrics deconvolution

If we consider only a few of the general requirements for the ideal polymer/additive analysis techniques (e.g. no matrix interferences, quantitative), then it is obvious that the choice is much restricted. Elements of the ideal method might include LD and MS, with reference to CRMs. Laser desorption and REMPI-MS are moving closest to direct selective sampling tandem mass spectrometry is supreme in identification. Direct-probe MS may yield accurate masses and concentrations of the components contained in the polymeric material. Selective sample preparation, efficient separation, selective detection, mass spectrometry and chemometric deconvolution techniques are complementary rather than competitive techniques. For elemental analysis, LA-ICP-ToFMS scores high. 

Fig. 9.12 Comparison of the measured reference spectra (dotted line) with the pure component spectra (solid line) obtained by chemometric deconvolution of the complex ATR FTIR spectra reported in Fig. 9.11.

Other examples presented in the literature are those based on the use of copolymeric disk-based sorbent materials for the isolation and preconcentration of nitro-substituted phenol isomers and the concurrent removal of potentially interfering matrix components followed by onhne simultaneous determination of individual species by diode array spectrophotometry, via chemometric deconvolution of the overlapped spectra, without the need for chromatographic separation. In contrast to bead-extraction, no flow impedance is observed when using extraction disks while better enrichment factors are obtained because of the improved specific surface area. Compared with earlier methods for isolation/preconcentration of nitrosubstituted phenols based on liquid-liquid extraction, these systems should be regarded as environmentally friendly approaches because the use of harmful organic solvents is circumvented. 

Sinha, A.E., Hope, J.L., Prazen, B.J., Fraga, C.G., Nilsson, E.J., Synovec, R.E. (2004a). Multivariate selectivity as a metric for evaluating comprehensive two-dimensional gas chromatography-time-of-fhght mass spectrometry subjected to chemometric peak deconvolution. J. Chromatogr. A 1056, 145-154. 

Chemometric methods can greatly increase the number of analyzable peaks in MDLC in particular, the generalized rank annihilation method (GRAM) can quantify overlapping peaks by deconvoluting the combined signal to those of each dimension. Standards with precise retention time are required, and there must be some resolution in both dimensions [60,61]. 

Fig. 13.5 Schematic representation of the use of chemometrics to deconvolute the multiplex spectrum of six dye-labeled oligonucleotides, (a) Shows the individual spectra of six dye-labeled oligonucleotides and (b) shows the spectrum of the mixture of the six labeled oligonucleotides...

Chemometries has played two major roles in MEKC for analysis of the data collected from the separation and detection of analytes, and for efficient optimization of the separation conditions. Regarding data analysis, chemometrics can allow deconvolution of poorly resolved peaks (15,16) and quantification of the corresponding analytes. Chemometrics can also be employed for multivariate calibration (17), characterization of complex samples, and to study peak purity. Sentellas and Saurina have recently reviewed the role of chemometrics applied to data analysis in CE (18). For MEKC in particular, chemometrics has been used more widely as a tool for optimization of separation conditions. The focus of this chapter is to exemplify the utility of chemometric methods for the optimization of separation conditions in MEKC. 

S.R. Gallant, S.P. Fraleigh and S.M. Cramer, Deconvolution of Overlapping Chromatographic Peaks using a Cerebellar Model Arithmetic Computer Neural Network, Chemometrics Intelligent Laboratory Systems 18 (1993), 41-57. 

See also Chemometrics and Statistics Experimental Design Optimization Strategies Multivariate Classification Techniques Multivariate Calibration Techniques Expert Systems Multicriteria Decision Making Signal Processing Spectral Deconvolution and Filtering. 

IR, Raman scrutinize homo/heteromolecular interaction (H-bonding, dipolar interaction), higher sensitivity of NIR for H-bonding (OH overtones/combinations) Amorphization generally weakens many inter-molecular interactions while strengthens some Overlapping peaks need deconvolution and multivariate data analysis for quantification, multi-component image analysis requires chemometric methods... 

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