Vol 72, No 2 (2017)

A generalized algorithm of the multivariate simulation of spectrometric data is considered for solving typical analytical problems, like the determination of the concentration of a particular analyte and the assignment of a sample to one of predefined classes. In particular, we considered preliminary data processing, exploratory analysis, optimization of a chemometric model, calculation of performance characteristics, transfer of the model to other spectrometers, and automation of chemometric processing for the routine analysis of samples. To illustrate the potential of the method, we selected a system of bovine and porcine heparin, mixtures of soy and sunflower lecithin, and a set of red and white wine samples as test samples. Partial least squares and discriminant analysis were used as chemometric methods. We used proton nuclear magnetic resonance (1H NMR) to record signals. Using the MATLAB environment, chemometric programs were developed for automated data processing in the context of problems under consideration and for the transfer of multivariate models to other spectrometers. Based on the results obtained, a methodology is proposed for the multivariate analysis of spectrometric data, which can be used in the analysis of various types of matrices and spectrometric signals.

A new calibration curve equation containing no empirical constants is proposed for calculating the concentration dependence of partial current in local voltammetry of heterogeneous alloys. A good agreement between the calculated and experimental data is found on an example of eutectic alloys Cd−Bi and Sn–Bi.

The nonuniformity of aerosol distribution over filter surface was studied. It was found that the distribution depends on the properties of the studied object and on the sampler type: particle concentration is often higher in the center of the filter, but in some cases, they shift to the edges; the uniform distribution of particles is observed rarely. It was shown that, if the emitter in X-ray fluorescence analysis (XRF) is a disk 3 cm in diameter cut from the center of a filter 5 cm in diameter, the systematic error of the results of analysis may be higher than 0.30. Recommendations on the choice of the conditions of sampling aerosols and emitter preparation are formulated. If these conditions are met, the results of XRF analysis of nonuniform filters are characterized by s_r = 0.05, which satisfies the admissible error.

A simple method of sample preparation, rapid screening, and determination of dyes—veterinary drugs and illegally used dyes (coloring product counterfeiters)—in spices by HPLC–high-resolution quadrupole time-of-flight mass spectrometry is proposed. Sample preparation involves the extraction of analytes from a solid matrix with acetonitrile containing 0.1% of formic acid, twofold dilution of the extract with deionized water, filtration, and chromatographic separation. The limits of detection were 0.01–0.4 ng/g. The procedure of screening and determination of dyes in foods includes the identification of dyes by an accurate monoisotopic mass of the ion (m/z), retention time (t_R), and coincidence of the isotopic distribution (mSigma), and, if dyes are detected, their determination by the standard addition method. The relative standard deviation of the results does not exceed 15%. The duration of the analysis is 1–2 h.

A procedure for the determination of 23 pesticides from different classes (organophosphorus and organochlorine compounds, synthetic pyrethroids, and triazoles) in cereal crops is proposed. It is based on sample preparation according to the QuEChERS method with the subsequent cleaning of the extract with natural aluminosilicate and the determination of analytes by gas chromatography with mass-spectrometric detection. The limits of the quantitative determination of pesticides are ~0.005 mg/kg. The relative standard deviation does not exceed 0.02. The duration of analysis is 35–40 min.

The possibility of identifying industry-related traces of oil contamination in biogenic sediments is investigated on an example of model oil-contaminated peat samples. It is shown that oil pollution of <1 wt % in biogenic samples cannot be identified using a conventional IR spectrometric procedure. An additional study of organic extracts, isolated in sample preparation, by solid-phase extraction and thin layer chromatography can detect specific oil aromatic hydrocarbons in contaminated samples uncharacteristic for background samples of the same type.

A nonenzymatic method was developed for the detection and quantification of hydrogen peroxide using metallic sols obtained by the reduction of silver compounds with sodium borohydride in the presence of a surface stabilizer. These sols changed color on exposure to aqueous solutions of hydrogen peroxide. The nature of the stabilizer used in sol preparation affects spectral characteristics of the final product formed in the reaction with hydrogen peroxide. In the case of polyvinyl pyrrolidone, the intensity of the surface plasmon resosnance absorption band at 405 nm decreased. In using cetyltrimethylammonium bromide, a signal at 519 nm appeared along with the similar decrease in the absorption band at 408 nm. The band intensity depends on the concentration of hydrogen peroxide. The described phenomena can form a basis for the development of procedures for the qualitative and quantitative determination of hydrogen peroxide in water bodies.

A review of publications on the creation and application of certified reference materials for the chemical analysis of geological materials and environmental objects with the aim to ensure the uniformity of measurements is presented.

A simple portable spectrophotometer was constructed and used to perform analytical experiments. The developed model uses available tools and materials such as light emitting diode lamps, compact discs, plastic and cardboard boxes and a cell phone camera to build a design that illustrates the major components of spectrophotometers. The spectra of serial concentrations of KMnO₄ (50‒600 μM) were recorded and the values of absorbance were extracted at λ_max to build the calibration curve. A linear relationship between the concentration and absorbance was obtained with the coefficient of determination 0.994. The model was also utilized to study the spectra of KMnO₄, phenolphthalein and bromothymol blue in comparison with a Shimadzu UV-1800 spectrophotometer as a reference instrument. In spite of the differences in the observed spectra, the recorded λ_max were almost identical to those measured by the developed model. The model was successfully used to determine the concentration of sodium alendronate through ligand-exchange complexation with ferric salicylate.