COMPARATIVE STUDY OF DIFFERENT THIRD-ORDER DATA GENERATION APPROACHES

ALCARAZ, MIRTA R.; MONTEMURRO, MILAGROS; SIANO, GABRIEL; CULZONI, MARÍA J.; GOICOECHEA, HÉCTOR C.

Barcelona

Congreso; Chemometric in Analytical Chemistry; 2016

Over the last years, it has been demonstrated that the increase of multiway data dimensions has a positiveimpact on analytical figures of merit, e.g. higher sensitivity, lower limits of detection and quantitation,better selectivity, among others. First- and second-order data analyses have become excellent tools forthe resolution of complex samples which would result experimentally challenging from the univariatecalibration standpoint. On the other hand, even though no additional analytical advantages have been yetproved, third-order data analysis for analytical applications constitutes a field worth to be explored [1].Although multidimensional instrumental signals are easy to be obtained with the available moderninstrumentation, and several chemometric algorithms have been successfully developed to solve multiwaydata problems, the way in which the multi-way data are generated may have a significant effect onthe final results. In this work, a comparative study of different third-order data generation approacheswas carried out. Three methods based on identical liquid chromatographic conditions but coupled todifferent emission and excitation fluorescence detection systems were developed for the quantitativeanalysis of antibiotics in aqueous matrices.The first approach included the collection of several fractions at the end of the chromatographicprocedure by means of a custom-built device that allows to collect fractions in a 96-wells ELISA plate.Then, emission and excitation spectra were registered for every fraction by using a spectrofluorometerequipped with a plate reader accessory coupled to an optical fiber and a gated photomultiplier. In thisway, 25 emission-excitation matrices (EEM, size: 17×25) were obtained for each chromatographic run.[2] A second strategy was developed by using a 10 µL flow-cell connected at the end of thechromatographic instrument and placed in a fast-scanning spectrofluorometer. Here, it was possible toregister sequential EEMs for a unique chromatographic run. Since the fast-scannig spectrofluorometertakes only few seconds to register each EEM, it was necessary neither to stop the chromatographic flownor to collect fractions after the chromatographic procedure, and 25 sequential EEMs (size: 7×45) wereobtained for each chromatographic run. Finally, a multi-chromatographic run method involving a liquidchromatographic instrument coupled to a fast-scanning fluorescence detector which allowed to registertime-emission fluorescence data matrices in a specific spectral range at a fixed excitation wavelengthwas developed. In order to build excitation-emission data matrices, eight chromatographic runs atdifferent excitation wavelengths (time-emission matrix size: 45×150) were required for the same sample.The three methodologies aforementioned were evaluated using different algorithms, such as PARAFAC,APARAFAC, PLS-RTL and MCR-ALS, and selectivity, sensitivity, robustness, and time processingwere evaluated. Since the data generation was different, each methodology required a particular data preprocessingincluding smoothing, peak alignment, and baseline correction, among others. Furthermore,due to differences in sensitivity provided by the implementation of a variety of detection mode it wasnecessary to assess several sample preparation methods in order to reach good analytical figures of merit.