On the Possibility of Universal Chemometric Calibration in X-ray Fluorescence Spectrometry: Case Study with Ore and Steel Samples

The accuracy of X-ray fluorescence spectrometry in quantitative element analysis depends on the particular sample composition (so-called matrix effects). Counteracting these effects requires a large number of calibration samples similar in composition to those under analysis. Application of the model constructed for a particular type of samples is not possible for the analysis of samples having a different matrix composition. A possible solution for this problem can be found in the construction of universal calibration models. We propose the development of these universal models using chemometric tools: influence coefficients—partial least squares regression (IC-PLS) and nonlinear kernel regularized least squares regression. We hypothesize that the application of these methods for constructing calibration models would allow embracing the samples of different types in the framework of a single model. We explored this approach for the case of two substantially different types of samples: ores and steels. The performance of these methods was compared with the fundamental parameters (FP) method, which takes into account matrix effects using theoretical equations and allows handling samples of different elemental composition. IC-PLS significantly outperforms traditional FP in terms of accuracy for predicting the content of Al (root mean squared error of prediction 0.96% vs. 3.87%) and Ti (0.05% vs. 0.09%) and yields comparable results for Si and Mn quantification in ores and steels

Signal Smoothing with PLS Regression

Smoothing of instrumental signals is an important prerequisite in data processing. Various smoothing methods were suggested through the last decades each having their own benefits and drawbacks. Most of the filtering methods are based on averaging in a certain window (e.g., Savitzky-Golay) or on frequency-domain representation (e.g., Fourier filtering). The present study introduces novel approach to signal filtering based on signal variance through PLS (projections on latent structures) regression. The influence of filtering parameters on the smoothed spectrum is explained and real world examples are shown

Foam-like Ce–Fe–O-based nanocomposites as catalytic platforms for efficient hydrogen oxidation in air

Foam-like nanocomposites of the Ce–Fe–O system with two (c-CeO2, am-F2O3), three (c-CeO2, o-CeFeO3, α-F2O3), or four phases (c-CeO2, o-CeFeO3, α-F2O3, am-Fe2O3) were synthesized using the RedOx reaction of glycine-nitrate combustion. The glycine/nitrate ratio (G/N) varied from deficient (0.2, 0.4) and stoichiometric (0.6) to excess ratios of glycine (0.8, 1.0, 1.2, 1.4). PXRD, 57Fe Mössbauer spectroscopy, N2-physisorption, TEM, H2-TPD, O2-TPD, and H2-TPR were used to examine the characteristics of the obtained samples. The average crystallite size of the obtained composites was in the range of 1.3–31.3 nm, 33.4–50.7 nm, and 10.1–33.9 nm for c-CeO2, o-CeFeO3, and α-Fe2O3, respectively. The lowest SBET (1.5 m2/g) belonged to the case of stoichiometric G/N, while the highest value (49.2 m2/g) was found in the case of the highest amount of glycine (G/N = 1.4); the latter case also had the largest total pore volume (Vp = 0.182 cm3/g) when compared to the others. Moreover, the advanced catalytic performance of foamy Ce–Fe–O-based nanocomposites toward H2 combustion in air was found with t10 = 275 °C, t50 = 345 °C, and Ea = 76.9 kJ/mol for sample G/N = 1.2. The higher activity of sample G/N = 1.2 in catalysis was attributed to different properties of the composite, including an appropriate component phase ratio, the smaller size of crystallites, higher specific surface area, higher reducibility,oxygen capacity, etc. The findings make it possible to carry out the directed synthesis of catalysts based on the Ce–Fe–O system with specific phases, dispersion, and morphological composition for efficient hydrogen oxidation at moderate temperatures

Combination of Total-Reflection X-Ray Fluorescence Method and Chemometric Techniques for Provenance Study of Archaeological Ceramics

The provenance study of archaeological materials is an important step in understanding the cultural and economic life of ancient human communities. One of the most popular approaches in provenance studies is to obtain the chemical composition of material and process it with chemometric methods. In this paper, we describe a combination of the total-reflection X-ray fluorescence (TXRF) method and chemometric techniques (PCA, k-means cluster analysis, and SVM) to study Neolithic ceramic samples from eastern Siberia (Baikal region). A database of ceramic samples was created and included 10 elements/indicators for classification by geographical origin and ornamentation type. This study shows that PCA cannot be used as the primary method for provenance purposes, but can show some patterns in the data. SVM and k-means cluster analysis classified most of the ceramic samples by archaeological site and type with high accuracy. The application of chemometric techniques also showed the similarity of some samples found at sites located close to each other. A database created and processed by SVM or k-means cluster analysis methods can be supplemented with new samples and automatically classified

Combination of Total-Reflection X-Ray Fluorescence Method and Chemometric Techniques for Provenance Study of Archaeological Ceramics

The provenance study of archaeological materials is an important step in understanding the cultural and economic life of ancient human communities. One of the most popular approaches in provenance studies is to obtain the chemical composition of material and process it with chemometric methods. In this paper, we describe a combination of the total-reflection X-ray fluorescence (TXRF) method and chemometric techniques (PCA, k-means cluster analysis, and SVM) to study Neolithic ceramic samples from eastern Siberia (Baikal region). A database of ceramic samples was created and included 10 elements/indicators for classification by geographical origin and ornamentation type. This study shows that PCA cannot be used as the primary method for provenance purposes, but can show some patterns in the data. SVM and k-means cluster analysis classified most of the ceramic samples by archaeological site and type with high accuracy. The application of chemometric techniques also showed the similarity of some samples found at sites located close to each other. A database created and processed by SVM or k-means cluster analysis methods can be supplemented with new samples and automatically classified

Foam-like Ce–Fe–O-based nanocomposites as catalytic platforms for efficient hydrogen oxidation in air

Foam-like nanocomposites of the Ce–Fe–O system with two (c-CeO2, am-F2O3), three (c-CeO2, o-CeFeO3, α-F2O3), or four phases (c-CeO2, o-CeFeO3, α-F2O3, am-Fe2O3) were synthesized using the RedOx reaction of glycine-nitrate combustion. The glycine/nitrate ratio (G/N) varied from deficient (0.2, 0.4) and stoichiometric (0.6) to excess ratios of glycine (0.8, 1.0, 1.2, 1.4). PXRD, 57Fe Mössbauer spectroscopy, N2-physisorption, TEM, H2-TPD, O2-TPD, and H2-TPR were used to examine the characteristics of the obtained samples. The average crystallite size of the obtained composites was in the range of 1.3–31.3 nm, 33.4–50.7 nm, and 10.1–33.9 nm for c-CeO2, o-CeFeO3, and α-Fe2O3, respectively. The lowest SBET (1.5 m2/g) belonged to the case of stoichiometric G/N, while the highest value (49.2 m2/g) was found in the case of the highest amount of glycine (G/N = 1.4); the latter case also had the largest total pore volume (Vp = 0.182 cm3/g) when compared to the others. Moreover, the advanced catalytic performance of foamy Ce–Fe–O-based nanocomposites toward H2 combustion in air was found with t10 = 275 °C, t50 = 345 °C, and Ea = 76.9 kJ/mol for sample G/N = 1.2. The higher activity of sample G/N = 1.2 in catalysis was attributed to different properties of the composite, including an appropriate component phase ratio, the smaller size of crystallites, higher specific surface area, higher reducibility,oxygen capacity, etc. The findings make it possible to carry out the directed synthesis of catalysts based on the Ce–Fe–O system with specific phases, dispersion, and morphological composition for efficient hydrogen oxidation at moderate temperatures.</p