Target Factor Analysis

Tam et al. [37-47] developed an impressive generalized method for the determination of ionization constants and molar absorptivity curves of individual species, using diode-array UV spectrophotometry, coupled to an automated pH titrator. Species selection was effected by target factor analysis. Multiprotic compounds with overlapping pK s have been investigated binary mixtures of ionizable compounds have been considered assessment of inicroconstants have been reported. 

P.J. Gemperline, A priori estimates of the elution profiles of the pure components in overlapped liquid chromatography peaks using target factor analysis. J. Chem. Inf. Comput. Sci., 24 (1984) 206-212. 

Tam, K. Y. Takacs-Novak, K., Multiwavelength spectrophotometric determination of acid dissociation constants. Part II. First derivative vs. target factor analysis, Pharm. Rese. 16, 374-381 (1999). 

MEEKC Microemulsion electrokinetic chromatography TFA Target factor analysis... 

Fig. 2.5. Measurement of pKas of serotonin by target factor analysis (TFA). (A) 3-D spectrum produced by serotonin in pH gradient experiment (equivalent to A matrix). (B) Molar absorptivity of three serotonin species (equivalent to E matrix). (C) Distribution of species (equivalent to C matrix). In this graph the three sets of data points denote the three...

All measurements in duplicate except acyclovir (x3) and labetalol (x5). Results obtained by First Derivative (FD) or Target Factor Analysis (TFA). 

The basic idea of Target Factor Analysis is very simple. In order to test whether a certain compound is taking part in the process, whether its spectrum exists in the measurement, we test whether that spectrum lies in V. If such a test spectrum is outside V, there is no doubt that the component does not take part in the process under investigation. If it is in the subspace, we cannot positively conclude that the species is there the test spectrum could be a linear combination of the existing spectra. 

Back to Target Factor Analysis. C is both a linear combination of E (equation (5.36)) and also of U (see later in equation (5.49)). Combining the two equations... 

The applicability of Eq. (2.63) was tested for some 180 individual solutes (with up to 10 carbon atoms) and 25 dry solvents by stepwise multivariable Unear regression and for 28 solutes and 9 dry solvents by target factor analysis essentially the same conclusions and universal coefficients were obtained by both methods. As an example of the application of Eq. (2.63), the distribution of succinic acid between water and chloroform (a dry solvent with = 0.0048) and tri-n-butyl phosphate (a wet solvent with Xw = 0.497) may be cited [13]. 

The thickness of pharmaceutical tablet coatings was predicted using target factor analysis (TFA) applied to Raman spectra collected with a 532-mn laser, where the samples were photobleached in a controlled manner before spectra were acquired. The authors acknowledge numerous issues that limit the direct applicability of this approach to process control. These include potential damage or alteration of the samples from photobleaching, laser wavelength selection, and data acquisition time. However, most of the issues raised relate to the hardware selected for a particular implementation and do not diminish the demonstration [286]. 

The diffusion of correlation methods and related software packages, such as partial-least-squares regression (PLS), canonical correlation on principal components, target factor analysis and non-linear PLS, will open up new horizons to food research. 

In the ATR FTIR study of the synthesis of cyclopentyl silsesquioxane 7F3, in situ ATR FTIR spectra of the reaction mixture were collected every 2 min during the reaction. The spectra obtained were plotted as a function of reaction time (Fig. 9.11). Pure component spectra and relative concentration profiles were subsequently recovered using a multivariate curve resolution (MCR) [59] technique based on a modified target factor analysis algorithm [60]. 

Target factor analysis is a suitable method for receptor modeling. The essence of this method is the correlation of one special influence, the target, with one factor from the factor solution. The factor solution is constrained into a shape such that the target correlates with one factor but not with the other factors. It is, therefore, possible to estimate the part of the variance from this special influence and to find other correlating features. 

Reverse-phase high-performance liquid chromatography Target factor analysis Unstirred water layer... 

Malinowski ER (1978) Theory of error for target factor analysis with applications to mass spectrometry and nuclear magnetic resonance spectrometry. Anal Chim Acta 103 359-354 Malinowski ER (1991) Factor Analysis in Chemistry. John Wiley, New York,... 

For overlapping peaks the data matrix contains linear combinations of the pure spectra of the overlapping components in its rows, and combinations of the pure elution profiles in its columns. Multivariate analysis of the data matrix may allow extraction of useful information from either the rows or columns of the matrix, or an edited form of the data matrix [107,116-118]. Factor analysis approaches or partial least-squares analysis can provide information on whether a given spectrum (known compound) or several known compounds are present in a peak. Principal component analysis and factor analysis can be used to estimate the maximum number of probable (unknown) components in a peak cluster. Deconvolution or iterative target factor analysis can then be used to estimate the relative concentration of each component with known spectra in a peak cluster. 

This method measures the UV change induced by ionization instead of the volume of titrant necessary to change pH. Spectrophotometric titration is a powerful technique that works with relatively low concentrations of analyte (factor 10—Slower compared to potentiometric titration), thus preventing sample precipitation for a larger proportion of the samples. The interpretation of experimental data is relatively easy when one considers a single ionization. It becomes significantly more complex if the molecule has several ionizable centers, and even more if they overlap. In this case sophisticated numerical procedures like target factor analysis have to be used. ... 

Target Factor Analysis. The TFA method has already been described elsewhere and is briefly described below ... 

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