Imbrie’s Q-Mode Factor Analysis Applied to Simultaneous Determination of Individual Amino Acid in Binary and Ternary Mixtures

Abstract

One of the most important problems in analytical chemistry is determining the number and concentration of chemical species in mixtures by means of spectroscopy and chromatography. A series of statistical techniques has been utilized to develop multivariate methods which extract information from spectra and chromatograms in order to identify the species present and to determine the concentrations of some or all of them. The applicability of each method depends on the data set submitted for analysis. From an analytical point of view, 1 the multivariate methods can be classified into three categories: I) spectral information is available for each individual species in the samples, II) spectral information about these species is incomplete or only partially known and, III) no information about the chemical compositions of the samples exists.This article proposes a multivariate calibration method to determine the chemical compositions of complex mixtures based on Imbrie's Q-mode factor analysis followed by varimax 2,3 and Imbrie's oblique rotations. 2 This method can be classified as one of category I as well as of category III, depending on the information available about the chemical system to be analyzed. For category I applications, this method does not require an extensive calibration set, as do the PCR, PLS, K-matrix and MLR methods. Only spectra of the pure absorbing species or standard spectra are necessary. In category III applications, the method is capable of identifying the number of absorbing species and their relative concentrations from only the set of spectra for the mixture being analyzed.An important requirement for applying all of the methods cited above is that the mixture spectra must be a linear combination of the individual spectra of the species involved, weighted by their respective concentrations. In other words, Beer's or an analogous law must be obeyed.Although quantitative analysis for amino acids is commonly used in clinical investigations, the food industry and research, there is no routine spectrophotometric method for their simultaneous determination in mixtures. In previous papers, 4 we proposed a method for the simultaneous determination of total amino acids and proteins using p-benzoquinone (PBQ). The reaction of PBQ and the amino acids was carried out at 100˚C for 20 min, since this reaction is very slow at ambient temperature. The products of the reaction have bands between 390 and 440 nm that follow Beer's law. Since this band is the resultant of a mixture of products, their individual simultaneous determinations are impossible by traditional methods, thus justifying the application of a multivariate analysis. In this report, individual amino acid determinations are discussed based on the application of Q-mode factor analysis to alanine-glutamine, threonine-glutamine and alanine-threonine binary mixtures and alanine-glutamine-threonine ternary mixtures. MethodologyThe objective of this analysis is to factor an nxp A matrix, formed by n objects (samples or mixtures) and p variabl...

Multivariate analysis of protolytic and tautomeric equilibria of Erythrosine B and its ester derivatives in ionic and non-ionic micelles

“…However, this spectral behavior makes it difficult to use this kind of methodology in determining the pKa. In such cases, multivariate analysis involving chemometric tools are relevant strategies, as previously reported in literature [24,25], by chemometric multivariate analysis using the Imbrie Q-mode method [26,27].…”

“…The proposed methodology for micellar systems is based on Q-mode, in which the relation between objects is more important. The specificity of the Q-mode is the step standardization, which is based on the definition of a proportionality relationship between objects, called cos θ [26,27,32,33]. This methodology is specially indicated in systems where no information is known a priori of the species [34].…”

Exploratory Analysis of Simultaneous Degradation of Anthocyanins in the Calyces of Flowers of the Hibiscus sabdariffa Species by PARAFAC Model

“…The methods can be divided in two groups: 1) Two-way resolution applicable to the resolution of single matrices, e.g. orthogonal projection (OPA), 10 Imbrie's Q-mode factor analysis followed by varimax and Imbrie's rotations, 11,12 correlated spectral data by procrustes rotation, 13 interative target transformation factor analysis (ITTFA), 14 and 2) three-way resolution methods applicable to the resolution of two or more matrices. 15 In the last two decades, multi-dimensional data arrays can be obtained using so-called hyphenated instruments such as a highperformance liquid chromatograph with a diode array detector (HPLC-DAD), an excitation/emission matrix spectrofluorometer, or a UV-Vis spectrophotometer equipped with a diode array detector for the acquisition of spectra as function of reaction time.…”

Simultaneous Spectrophotometric Determination of Hg2+, Pb2+, and Cu2+ by Zn(dmit) Using the Multivariate Calibration Method

“…Shi et al 10 developed the Kalman Filter method for simultaneous determination of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II). Scarmínio et al 11,12 developed a calibration multivariate method for systems with severe UV-Vis band overlapping, through Imbrie's Q-type factor analysis, followed by varimax and oblique rotations and the K matrix method. This methodology was used for the simultaneous determination of alanine and threonine in a mixture using pbenzoquinone (PBQ) as reagent.…”