Volume 79, Nº 11 (2024)

A non-contact method for determining the mass fraction of milk fat in bottled milk by diffuse reflection of radiation from LEDs with radiation wavelengths of 365, 390, 850 and 880 nm using a smartphone and a special device is proposed. To register the analytical signal, the OnePlus 10 Pro smartphone, iPhone 14 with PhotoMetrix PRO®, ColorGrab, RGBer applications installed, and an IR spectrometer with Fourier transform for the near-infrared region (4000–10000 cm^–1) were used. The experimental data were processed using specialized programs TQ Analyst, The Unscrambler X, XLSTAT. Simultaneous participation in the study of all LEDs with different wavelengths was found to contribute to obtaining results with the smallest relative deviation compared with the use of individual LEDs. A slight change in diffuse reflection from milk through polyethylene terephthalate-based packaging was revealed, which makes it possible to conduct the analysis in a non-contact way without opening the packaging. The milk fat content in the analyzed milk samples was estimated using a multidimensional data grading algorithm – partial least squares regression. The relative standard deviation of the analysis results did not exceed 0.08. The equivalence of the results obtained during the analysis was confirmed by using the method of IR spectroscopy with Fourier transform in the near spectral region

A method for the determination of acetone acylhydrazones has been developed based on the formation of a colored complex with copper(II) ions in ammonia solutions of the composition Cu : reagent = 1 :2, its subsequent extraction with chloroform and measurement of the light absorption of extracts at 553 nm (ε = 128 l/(mol·cm)); the linear range of determined concentrations is 80.0–590.0 mg/l; relative error <2.80%). Using the example of heptanoyl hydrazone acetone, it is shown that the reagent in the composition of the complex compound is quantitatively extracted in the pH range of 7–10 with a single extraction for 3 minutes; a two-fold excess of copper(II) is sufficient for its complete extraction. The spectra of homologue complexes of the studied series of acetone acylhydrazones are similar. The spectrophotometric method has established high hydrolytic stability of reagents in a narrow range of pH values 9–10. The technique has been tested on solutions obtained by studying the adsorption of reagents on chalcopyrite. The correctness of the analysis results was verified by the additive method.

The study is devoted to the peculiarities of the determination of zinc in dust emissions from gas purification of electrometallurgical production using scrap metal for processing. By X-ray phase, energy dispersive X-ray fluorescence analysis (EDXRF) and atomic emission spectrometry with inductively coupled plasma (ICP-AES), elemental and phase (zinc oxide and ferrite, halite, sylvin and magnetite) compositions of gas purification dust emissions were established, taking into account which an analysis scheme was developed. The developed technique of express energy dispersive X-ray fluorescence determination of zinc in dust emissions of gas purification provides for the construction of a calibration dependence with correction of matrix effects. The relative deviation in the determination of zinc by the EDXRF method, taking into account the matrix correction, was 2.1%, ICP-AES – 2.5%. The method for determining zinc was tested on real samples of dust emissions from gas purification.

The composition of solid solutions in the KNd(SO₄)2·H₂O–SrSO₄·0.5H₂O system synthesized from aqueous solutions of KCl, NdCl₃, SrCl₂ and H₂SO₄ was studied by X-ray fluorescence analysis. By the method of least squares, the coefficients of the calibration dependences of intensity on the concentration of the determined elements Nd, Sr, K. For the determination of potassium, a linear approximation function was used, for the determination of neodymium and strontium, a parabolic approximation function was recommended. The obtained dependences are characterized by a low (<1%) relative approximation error. In the range of detectable concentrations (wt.%) K 0.863–8.892, Sr 8.41–38.03 and Nd 5.296–29.30 the standard deviation was 0.012–0.028, 0.008–0.098 and 0.05–0.27 respectively.

The transition from the traditional C18(I) stationary phases with nonpolar endcapping to the C10CN(II) phase has been shown to contain the terminal polar group leading to a change in selectivity comparable to an increase in the activity of residual silanol groups in phases I. The effect was found in the separation of isomeric monocopheoylquinic acids. Two variants of gradient modes have been proposed using a column of Diaspher-110-C10CN and aqueous acetonitrile, acidified H₃PO₄ components of the mobile phase for the separation of chlorogenic acids and caffeine from green coffee extracts from various manufacturers. The proposed chromatographic method has been shown as the method that can be used to determine trigonelin, the retention of which increased markedly when phase I was replaced by phase II. The proposed method is used to differentiate the fruits of two types of coffee – Arabica and robusta. It was found that robusta coffee extracts contain a higher amount of chlorogenic acids and caffeine.

The possibility of controlling the dynamics of the formation of the aroma of chocolate glaze during concoction using an artificial sense of smell system based on an “electronic nose" with modified polymers with gas piezosensors is shown. Samples were taken in real production and their mandatory control was carried out according to standard properties during the technological process of concocting chocolate glaze. Digitization and objective control of the process of development and maturation of the chocolate glaze flavor was carried out using a data matrix (recorded and calculated signals) of an array of piezosensors. An array of sensors has been pre-optimized, the responses of which correlate with individual physico-chemical indicators of the quality of semi-finished products and finished products. The correlation of the results of sensorometric analysis and physico-chemical indicators of the quality of confectionery glaze was carried out. Informative sensors have been selected, the responses of which allow rapid assessment of standard characteristics – humidity (based on the signal of a sensor based on crown ether with a Pearson correlation degree of R = 0.91), acidity (based on the signals of a sensor based on Twin-40 with a Pearson correlation degree of R = 0.90–0.91). The most valuable information is provided by monitoring the decrease in the content of non–volatile compounds – the total sugar content when conching using signals from a Triton X-100 sensor (with a Pearson correlation degree of R = 0.89). As a criterion for reproducibility of qualitative and quantitative composition, a new digital characteristic of the fragrance is proposed – a set of parameters of the binary sensitivity of the sensors of the “electronic nose”, and a new method of chemometric processing of data sets for objects of analysis has been developed. The possibility of introducing an “electronic nose” into production for technological control of compliance and optimization of formulations, the process of concocting chocolate glaze according to physico-chemical parameters and digital characteristics of the most unstable property – flavor, objective and reproducible assessment of the quality of confectionery products is shown.

Production and socio-environmental requirements for the quality of land waters have determined the need to create a network of hydrochemical observation posts, and the variability of controlled indicators – the need to perform routine chemical analytical studies. The standard (rigid) statistical methods of processing measurement results common in analytical chemistry, as a rule, underestimate the specifics of studying noisy (fuzzy) experimental data, which are the series of values of the impurity concentration of a river stream in space and time. It is shown that in this case, alternative soft computing tools designed to process exactly such data based on neuro-fuzzy hybrid algorithmic structures related to the ANFIS architecture are appropriate. The arrays of chemical analytical data on copper and zinc analyzed in this way on the Volga River, depending on water flow at different distances from the shore and depths, made it possible to identify the complex oscillatory behavior of concentrations of both substances in the water stream. It is concluded that the neuro-fuzzy scheme for processing monitoring results provides an opportunity for in-depth study of poorly understood processes of hydrochemical dynamics in systems far from thermodynamic equilibrium, which include natural watercourses.