The application of laser induced breakdown spectrometry for the quantitative determination of gold and silver in Au–Ag–Cu alloys is proposed. Laser induced plasma emission spectra in the ultraviolet region were studied in order to characterize the spectral information from time-integrated data. The multivariate calibration method known as partial least squares regression type 1 was used for calibration and prediction purposes. Satisfactory results were obtained for the determination of gold and silver without temporal resolution strategies. Since the employment of this chemometric algorithm was a good alternative for simplification of the experimental setup, a rapid, simple and low cost method is thus proposed for the determination of noble metals in jewelry pieces.

Soft Independent Modeling of Class Analogy and Partial Least Squares Regression were used in this work for the identification and quantification of thiamine, riboflavin, nicotinamide and pyridoxine by UV-Vis spectrophotometry, without separation or preconcentration steps in the analytical procedure. For quantitative purposes, the working range established was 1-14 mg L-1 for riboflavin, 2-26 mg L-1 for thiamine, 2-30 mg L-1 for nicotinamide, and 2-22 mg L-1 for pyridoxine. Recovery results higher than 95% were obtained in all cases during the analysis of synthetic and commercial samples. In the screening of each target vitamin, a classification model was built with two classes: (i) with the vitamin of interest, and (ii) without it. The discriminate capability of each classification model was evaluated for learning, independent testing and commercial samples, resulting in satisfactory findings with exception of riboflavin. Thus, a simple and reliable method is proposed for the simultaneous estimation of these compounds.

A new, simple spectrophotometric method for resolution of dye binary mixtures is proposed in this work. A simple mathematical algorithm was designed, in which the data are used from four linear regression calibration equations: two calibrations for each component at two selected wavelengths. The method of Kaiser was applied for the selection of the optimum two-wavelength sets for all mixtures under study. The recovery experiments were carried out in ten mixtures of the following dyes: Tartrazine, Amaranth, Erythrosin B, Sunset Yellow and Allura Red. The obtained results were compared with the results of a commonly used derivative spectrophotometric procedure (zero-crossing technique). The statistical evaluation of the method bias was performed and it was concluded that the proposed methodology may be competitive with the derivative procedure for the resolution of such dye binary mixtures.

The simultaneous spectrofluorimetric determination of aromatic polycyclic hydrocarbons of environmental interest, namely benzo[a]pyrene, benzo[e]pyrene, benzo[ghi]perylene, coronene, dibenzo[a,h]anthracene and indeno[1,2,3-cd]pyrene, in micellar media by using the non-ionic surfactant polyoxyethylene 10 lauryl ether (POLE) was investigated. In order to employ the highest sensitivity signals for the determination of each of the compounds in the mixture, the corresponding linear variable angle fluorescence spectra were recorded. Owing to the high spectral overlap observed, resolution of the multicomponent system was carried out by applying known algorithms such as multiple linear regression, partial least squares regression type 1 and artificial neural networks. The results obtained for both synthetic mixtures and water samples of two different origins spiked with known amounts of hydrocarbons of interest were satisfactory.