An X-ray fluorescence (XRF) technique has been developed for analysis of zinc–aluminum–magnesium alloys, which allows for determination of Mg, Al, Pb, Si, Mn, Fe, and Ni. The effect of the sample preparation method on the linear range of calibration plots for element determination has been assessed and conditions for XRF determination of the major alloying elements (Al and Mg) and impurities (Pb, Fe, Cu, Si, Mn, and Ni) have been studied. We have proposed that the matrix effect be corrected by choosing alpha-coefficients from X-ray intensity, followed by automatic conversion of the function to linear form. Calibration curves for determination of Mg (in the range 0.00019–5.04

We have studied conditions of oxysulfide determination in structural steel by spark atomic emission spectrometry (SAES) using an ARL iSpark Model 8860 spectrometer fitted with the Spark-DAT program option for spark diagram processing. In addition, to improve characteristics of calibration curves for determination of Al, Ca, Mn, and sulfur forming nonmetallic inclusions (NMIs), we used structural steel composition standards. The results demonstrate better sensitivity of Al and Ca determination and an increase in correlation coefficients of calibration curves for Mn and sulfur determination. Since no oxysulfide reference standards are available, the percentage of Al2O3MnS, Al2O3MnSMgO, Al2O3MnSCaS, Al2O3CaOCaS, Al2O3CaOMgOCaS in steel was pre-evaluated in accordance with the ASTM E1245 Standard (method 3) by scanning electron microscopy (SEM) with the use of an energy dispersive electron probe spectrometry (EDS) system. The results indicate that, in SAES determination of oxysulfides in structural steel, it is reasonable to use corrected algorithms for computer processing of the integrated spectrum, in combination with a pseudoformula. A proper algorithm and a pseudoformula for determination of each component were chosen with the use of Student’s t-test statistic by comparing the percentages of NMIs determined by SEM/EDS and SAES. We chose the spark range and analytical signal integration delay time for Al, Ca, Mg, Mn, and sulfur and confirmed the correctness of results of SAES determination of oxysulfides in the range from 500 to 1900 sparks (texp = 0.01) at a signal integration delay time of 110 μs (texp = 0.23). The technique for SAES determination of the total percentage of oxysulfides was tested in analysis of industrial structural steel samples. The results confirmed that there was no systematic error and that correct determination data were obtained (texp < 4.30). The proposed technique for NMI determination allows the analysis time to be reduced from 18 h (SEM/EDS) to 10 min.

A method for the determination of Fe tot , SiO 2 , P, V 2 O 5 , TiO 2 , Cr 2 O 3 , Ni, Cu, and Zn in iron ore raw materials (i.e., pellets, iron ore agglomerate, aspiration dust and slag component of scrap) by the method of atomic emission spectrometry with inductively coupled plasma (ICP-AES) has been developed using microwave sample preparation in analytical autoclaves. The composition of the acid mixture for the complete dissolution of the sample component was proposed, and the parameters of microwave decomposition, excluding the depressurization of the autoclave and the loss of sample elements which form volatile compounds, were selected. The developed method of microwave sample preparation in closed autoclaves made it possible to decompose iron ore samples using the minimum amount of acid (17 cm 3 ) in 45 min. Conditions for the determination of normalized elements in iron ore samples by the ICP-AES method after microwave sample preparation were determined: the operating parameters of the spectrometer were optimized, the analytical lines of each determined element free from spectral overlaps were selected, and the efficiency of using cadmium as an internal standard was experimentally proved. The equations for calibration dependences and the ranges of determinable contents are presented. When using cadmium as an internal standard in the analysis of iron ore, a decrease in the value of the standard deviation from 0.17 to 0.04 is observed when determining Cr 2 O 3 ; from 0.02 to 0.004 when determining Fe; from 0.03 to 0.002 when determining SiO 2 ; from 0.015 to 0.008 when determining TiO 2 ; and from 0.17 to 0.02 when determining V 2 O 5 . The correctness of the determination of the standardized elements by the developed method is evaluated using certified reference samples (CRS) similar in composition to the analyzed material. The results of determining the standardized elements according to the developed methodology were compared with the data obtained using GOST-approved methods of analysis and then checked in accordance with the recommendations of RMG 76-2014. The developed ICP-AES technique is characterized by a wider linear range of the determined concentrations than that in GOST-approved techniques, thus providing determination of the components in iron ore raw materials that could not be controlled before.

A technique for X-ray fluorescence spectral analysis of zinc-aluminum- magnesium alloys has been developed, which allows the determination of Mg, Al, Pb, Si, Cu, Mn, Fe, Ni content in the alloy. The effect of the sample preparation method on the linearity of calibration graphs is revealed. The conditions for determining the main alloying (Al, Mg) and impurity (Pb, Fe, Cu, Si, Mn, Ni) elements by X-ray fluorescence spectrometry were studied. It is proposed to use the correction of the matrix effect by selecting alpha coefficients for the intensity of X- ray radiation with subsequent automatic conversion of the function into a linear form. Calibration graphs for determination of the elements in the corresponding ranges, i.e., Mg (0.00019 – 5.04%), Al (0.0002 – 12.4%), Pb (0.0012 – 2.07%), Si (0.0005 – 0.12%), Cu (0.0006 – 5.95%), Mn (0.0004 – 0.00524%), Fe (0.0009 – 0.41%), Ni (0.0009 – 0.27%), were obtained using standard reference samples and production samples of the alloys, the chemical composition of which was previously determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The correctness of the developed methodology was confirmed by analysis of standard samples and comparative analysis of the obtained results using the Student’s t-test.

A technique for the determination of aristolochic acid (AA) in food products using a piezoelectric immunosensor is presented. Magnetic carbon nanocomposites (MCNC) were used as the recognition layer of the sensor, on the surface of which protein conjugates of AA were immobilized. Abstract-Methods for the synthesis of Fe 3 O 4 magnetic nuclei and their attachment to the surface of multi-walled carbon nanotubes (CNTs) have been studied. Using IR spectrometry, it was found that the formation of the recognition layer of the sensor occurs due to the formation of covalent bonds between the amino groups of AA conjugates and carboxyl groups of CNTs. The concentrations of protein conjugates based on ovalbumin (OVA) and bovine serum albumin (BSA) (0.3 and 0.2 mg/ml) and the degree of antibody dilution (0.25) were determined, which provide optimal characteristics of the piezoelectric immunosensor. The metrological characteristics of the method for determining AA have been established. The range of determined concentrations of AA and the limit of detection when using a piezoelectric immunosensor with a recognition layer based on MUNA/AA-OVA and MUNA/AA-BSA are (ng/ml): 50 – 400 and 10; 100 – 300 and 50, respectively. The sensor has been tested in the determination of AA in samples of Chinese herbal tea and dietary supplements for weight loss. No acid was found in tea, and in dietary supplements, the acid content is 3.2 μg/g.

Conditions for determining oxysulfides in construction steel by spark atomic emission spectrometry (SAES) using an ARL iSpark 8860 spectrometer which is equipped with a Spark-DAT software function for processing spark diagrams are studied. To improve the characteristics of the calibration curves for the determination of Al, Ca, Mn and sulfur forming non-metallic inclusions (NMI), we used certified reference materials of the composition of construction steels. An increase in the sensitivity of Al and Ca determination and correlation coefficients of calibration curves for the determination of Mn and S is shown. The concentration of Al 2 O 3 MnS, Al 2 O 3 MnSMgO, Al 2 O 3 MnSCaS, Al 2 O 3 CaOCaS, Al 2 O 3 CaOMgOCaS in steels was preliminarily determined using a combination of scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS) according to ASTM E1245 (method 3) in the lack of certified reference materials with oxysulfides. It is shown advisable to determine the concentration of oxysulfides in construction steels by SAES using corrected and developed algorithms for software processing of the integrated spectrum in combination with a pseudo-formula. It is shown expedient to select the appropriate algorithm and pseudo-formula on the basis of Student's test statistics by comparing the NMI concentrations obtained by SEM-EDS with SAES results. The spark intervals and the delay time of the analytical signal integration for Al, Ca, Mg, Mn, and sulfur are compared. The correctness of the oxysulfide determination by SAES was confirmed in the range of 500 – 1900 sparks ( t exp = 0.01) and the signal integration delay of 110 μsec ( t exp = 0.23). Test method for measuring the total concentration of oxysulfides by SAES was tested on production samples of construction steels. The absence of a systematic error and the correctness of the measurement results ( t exp < 4.30) were proved. It is shown that the developed method for determining the NMI concentration provides drastic reduction of the duration of the analysis from 18 hours (SEM-EDS) to 10 min.

A piezoelectric sensor with a recognition layer based on magnetic carbon nanocomposites, including multi-walled carbon nanotubes, magnetic Fe 3 O 4 nanoparticles, and polymer nanospheres with molecular imprints of erythromycin and azithromycin, obtained by the “core–shell” method, is developed. Silicon dioxide particles are used as cores, on the surface of which a shell molecularly imprinted with macrolides is synthesized by free radical polymerization or the sol–gel method. SiO 2 particles are obtained by the Stober method by varying the ratio of reagents during the synthesis. The size of the cores and nanoparticles of molecularly imprinted polymers ( MIP ) is determined by atomic force microscopy, and the density and uniformity of the layer on the surface of magnetic carbon nanocomposites ( MCNC ) are determined by the piezoelectric quartz crystal microbalance method. The optimal ratio of the reagents (template : functional monomer : cross-monomer) is established by a spectrophotometric method during the synthesis of “core–shell” nanostructures by free radical polymerization. A thin shell of SiO 2 with imprints of an antibiotic based on organosilicon compounds used in the synthesis of the core is formed by the sol–gel method on the surface of the silicon dioxide core. The sensor recognition layer is formed under the action of an external magnetic field. The dependence of the analytical signal of the sensor based on MIP@SiO 2 /MCNC on concentration is linear in the range 5–160 µg/mL for azithromycin and 10–160 µg/mL for erythromycin, and with a recognition layer based on SiO 2 @SiO 2 /MCNC, in the concentration range 20–400 µg/mL for erythromycin.

Conditions for the formation of a recognition layer of a piezoelectric immunosensor based on magnetic carbon nanocomposites (MCNCs) under the action of an external magnetic field are studied. The effects of the size and number of magnetic nanoparticles (MNPs) in the composite on the analytical characteristics of the gravimetric immunosensor are revealed. Scanning electron microscopy is used to determine the average sizes of Fe 3 O 4 magnetic nanoparticles synthesized by coprecipitation. It is noted that the minimum weight and stability of the recognition layer were observed for the nanocomposite obtained at a ratio of carbon nanotubes and MNPs with an average diameter of 22 nm equal to 3 : 1. The formation of peptide bonds between the MCNCs and a penicillin G conjugate was established by IR spectrometry. It was shown that the use of magnetic carbon nanocomposites in the formation of a recognition layer makes it possible to significantly simplify the procedure for preparing a piezoelectric sensor for analysis and reduce its duration from 24 to 1.5 h. The range of the determined antibiotic concentrations is 1–450 ng/mL, the limit of detection is 0.5 ng/mL.

Scientific relevance. Lyophilisation is the preferred method at the National Collection of Pathogenic Microorganisms (NCPM) of the Scientific Centre for Expert Evaluation of Medicinal Products of the Ministry of Health of the Russian Federation. Lyophilisation is used to provide for high standards of test-strain deposition, storage, and transportation and to ensure that test strains maintain their properties. Successful lyophilisation requires conducting experiments to establish the key parameters and critical conditions of the process.Aim. The study aimed to evaluate the effects that the speed and time of freezing, the time of drying, the fill volume of ampoules, and the density of cotton filters have on the quality of NCPM indicator microorganisms lyophilised in a manifold-type apparatus.Materials and methods. Pseudomonas aeruginosa NCTC 12924, Staphylococcus aureus NCTC 10788, and Salmonella Abony NCTC 6017 were freeze-dried using a manifold-type apparatus (M. S. R. 18, Usifroid). The authors used a low-temperature freezer at –70±2 °C for slow freezing and a mixture of dry ice and alcohol for quick freezing. The statistical analysis was performed using Microsoft Excel and Statistica 10.Results. The minimum time needed for freezing the samples in a low-temperature freezer at –70±2 °C was 4 hours. Further storage at this temperature for up to 1 month was shown possible without compromising the quality of the final product. The time needed for freezing the samples in a mixture of dry ice and alcohol was under 1 minute. No differences in quality parameters were observed between the lyophilised samples frozen slowly or quickly, except for the cake appearance. Quick freezing resulted in cakes that were non-uniform, crumbled, and pulled away from the ampoule walls, which is considered undesirable. The primary drying stage for ampoules with a fill volume of 0.2 mL took 6–8 hours. The secondary drying stage of 11, 18, 35, and 59 hours resulted in comparable lyophilisate quality: the authors observed no statistically significant differences in viable cell counts (CFU/mL) at the end of lyophilisation and at the end of stress testing. The residual moisture content after 59-hour secondary drying was less than 2%. The cotton filter density had a critical influence on the lyophilisate quality. Therefore, the authors recommend using cotton filters weighing 50 mg or less.Conclusions. The authors analysed the main stages of the lyophilisation process used for NCPM test strains and considered the effects that the speed and time of freezing, the time of drying, the fill volume of ampoules, and the density of cotton filters have on the quality of the final lyophilised product. The NCPM has implemented the results of this study in its work.

An urgent task is the synthesis of artificial receptors capable of selective binding and recognition of various molecules. One of the methods for obtaining such receptors is to obtain molecular imprints on a polymer matrix. The synthesis of MIP by polymerization in Pickering emulsion is relatively new and quite promising due to the high stability of emulsions and the use of environmental particles.

One of the factors influencing the uncertainty of residual moisture measurements in biological medicinal products is the accumulation of electrostatic charge on the surfaces of weighing bottles and laboratory balances, which results in poor weighing reproducibility. The authors believe that the simplest and most economical solution to this problem is to use weighing bottles made of a conductive material, e.g. metal. The aim of the work was to evaluate the influence of the material of weighing bottles on the reproducibility of loss-on-drying (LOD) methods. Materials and methods: Model samples for the study were prepared from a sucrose-gelatin medium by lyophilisation and subsequent moisture sorption to achieve a certain residual moisture content. The authors assessed the samples’ mass uniformity using Shewhart’s X-charts, and analysed their residual moisture content using a loss-on-drying procedure with glass and metal weighing bottles. Statistical processing of the results was carried out by calculating the main statistical indicators: Student’s t-test and Fisher’s F-test. Results: Four batches of model samples were prepared and standardised in terms of average mass using Shewhart’s charts. The effect of weighing bottle materials was most pronounced at low residual moisture contents (less than 0.5%), with the relative standard deviation (RSD) values for the results obtained with glass and metal weighing bottles reaching 76% and 35%, respectively. For the samples with a higher residual moisture content (2–5%), the minimum RSDs with glass and metal weighing bottles were 15% and 6%, respectively. Conclusions: The study allowed for evaluating the influence of the material of weighing bottles on the results of LOD measurements and demonstrated a higher reproducibility with metal weighing bottles. This confirms the possibility of using metal weighing bottles in quality assessment of biological medicinal products for human use with LOD methods.

A piezoelectric immunosensor with a recognition layer based on magnetic carbon nanocomposites is developed for the determination of ciprofloxacin. The receptor coating of the sensor is formed by the action of a magnetic field on magnetic particles located on the surface of carbon nanotubes modified with a ciprofloxacin conjugate. The sizes of magnetic particles in the composition of the nanocomposite are determined by scanning electron microscopy. A dependence of the mass of the recognition coating on the size of magnetic particles on the surface of carbon nanotubes is shown. A detection cell with a sensor located above a neodymium magnet is proposed. The analytical characteristics of the immunosensor are determined, the limit of detection for ciprofloxacin is 2 ng/mL, and the linear range of determined concentrations is 5–400 ng/mL. The use of magnetic carbon nanocomposites in the creation of a recognition layer ensures the reduction of the time of sensor preparation to analysis from 24 to 1.5 h and extends its service life. The sensor is tested in the detection of antibiotics in milk and meat.

Methods for the high-sensitivity determination of fluoroquinolones using a piezoelectric immunosensor based on multi-walled carbon nanotubes (MWCNTs) are developed. The use of MWCNTs in the formation of a stable piezoelectric sensor detection layer increases the active specific surface area which is necessary for receptor molecule binding. The concentrations of hapten-protein conjugates (35/65 serial concentration) and polyclonal antibodies are determined in the direct (15/85 for levofloxacin, 18/82 for ciprofloxacin) and in the competitive immunoassay formats (14/86 for levofloxacin, 10/90 for ciprofloxacin). Conditions for the analysis in the flow-injection mode were studied. The carrier flow rate was 30 and 50 mu l/min depending on the detection layer formation method. The characteristics of MWCNTs-based piezoelectric immunosensors were characterized for the determination of fluoroquinolones in the static and in the flow-injection modes. The direct and competitive immunoassay formats (detection limit, linear range of target concentrations, reproducibility) were determined. The detection limits were 9 and 8 ng/ml for levofloxacin and ciprofloxacin in the competitive format and 25 and 21 ng/ml in the direct assay. The piezoelectric immunosensors were employed for the analysis of milk.

Piezoelectric gravimetric sensors based on magnetic nanocomposites: polymers with molecular imprints (MIP) Fe3O4@MIP N - (phosphonmethyl) - glycine have been developed. It was found that the optimal concentration ratio of template: functional monomer: cross-monomer is 1: 3: 25. The best synthesis time is 3h with constant stirring at a speed of 60 rpm and heating to 60 °C.

Magnetic polymers with tetracycline molecular imprints have been synthesized. The conditions for the formation of a recognition layer of a piezoelectric sensor based on Fe3O4@MIP particles have been studied. It is shown that the use of the developed nanomaterial makes it possible to reduce the time required to prepare the sensor for analysis by 25 times in comparison with traditional methods.

A technique for analysis of secondary tungsten-containing raw materials (tungsten-containing sludge) using inductively coupled plasma atomic emission spectrometry in combination with microwave autoclave sample preparation has been developed. The composition of the acid mixture and algorithm of microwave heating of the autoclave are chosen to provide a complete quantitative transfer of the sample into a convenient analytical form for subsequent ICP-AES determination of the main components (heating of the sample to 220°C in the acid mixture of NH 4 F, HNO 3 , and HCl provides a quantitative transfer of its components to be determined into the solution). Analytical lines free from spectral interference were selected to determine Ti, Cr, Fe, Co, Ni, and W. We used real industrial samples of secondary raw materials obtained in product manufacture from VK-type hard alloys [solid solution of tungsten carbide grains (WC phase) in cobalt (Co phase)] in the form of tungsten-containing powders, grinding sludge of solid sintered alloys, dust waste, defective mixtures, waste of ventilation systems, and carbide powders. Correctness of the determination of elements was proved in analysis of ferrotungsten standard samples upon determination of the matrix component (tungsten) and by the methods of additives and sample weight variation upon determination of the alloying elements and impurities. The method of internal standard (with Sc as the element of comparison) was used to improve the precision and accuracy of the tungsten determination. The relative standard deviation was thus reduced from 0.03 to 0.004. The developed precise rapid technique was tested in analysis of industrial samples of secondary tungsten-containing sludge of hard alloys. The technique is recommended to control the composition of the secondary tungsten-containing sludge of hard alloys in a wide range of concentrations.

A set of ICP-AES techniques has been developed for determination of rated elements: Ti, Si, P, Al, Cu, Mo, V, Sn, and Zr in ferrotitanium; Ni, Fe, Cu, Co, and As in ferronickel; Si, Cr, and P in ferrochrome silicon; Zr, Si, Al, P, and Cu in zirconium ferrosilicon; Mn, Si, and P in manganese ferrosilicon. Combination of the multielement ICP-AES method which allows precise determination of the elements in ferroalloys in a wide range of concentrations and the microwave preparation of samples in closed autoclaves which excludes the loss of the components to be determined provides the rapidity of the analysis procedure. The composition of solutions for opening samples of ferroalloys and the temperature–time modes of microwave sample preparation in an autoclave are substantiated. Conditions for ICP-AES determination of the rated elements in ferroalloys are studied. Analytical lines of the elements to be determined free from significant spectral overlaps are chosen. The dilution rates of the solutions are determined. The method of internal standard was used to improve the reproducibility of the analytical signal for Ti determination in ferrotitanium, Si and Cr in ferrochrome silicon, and all rated elements in manganese ferrosilicon and ferronickel. The spectrometer was calibrated using model solutions and solutions of standard samples with additions of the certified solutions of the elements to be determined. To determine Ti, Si, P, Al, Cu, V, and Zr in ferrotitanium; Ni, Fe, Cu, and Co in ferronickel; Si, Cr, and P in ferrochrome silicon; Zr, Si, Al, P, and Cu in zirconium ferrosilicon; Si and P in manganese ferrosilicon, a multidimensional graduation by two analytical lines was used. The correctness of the determination was evaluated in analysis of standard samples of ferroalloys and comparative analysis of the obtained results with the data of standard methods: comparison of the variances according to the Fisher criterion did not reveal any significant difference between them, whereas the use of the modified Student test showed the absence of a systematic error.

Conditions of the synthesis of nanoparticles of ractopamine molecularly imprinted polymers (MIP) by the precipitation method are studied. It is shown that the size and dispersity of MIP particles are largely determined by the nature of the functional and cross-monomers and by the synthesis conditions: temperature, mixing rate, duration of synthesis, and ultrasonic treatment of the polymerization mixture before and after the synthesis. It is found that ractopamine MIP particles based on methacrylic acid and ethylene glycol dimethacrylate, sonicated for 30 min, have a minimum size and degree of dispersion. Using the piezoelectric quartz micro-weighing method, characteristics of the recognition layer based on MIP nanoparticles are found, and the analytical characteristics of a sensor for the determination of ractopamine in an aqueous solution are calculated.

A procedure for determination of Ag, As, Bi, Fe, Ni, Pb, Sb, Sn, Zn, and Cu in copper alloys using ICP AES with spark sampling has been developed. Spark sampling conditions were specified when studying the effect of discharge parameters on the line intensity and relative standard deviation (sr) (the discharge power level changed from 1 to 9 units on the SSEA scale (from 2.10 to 3.30 kW), discharge frequencies and pre-firing time ranged within 100 to 800 Hz and 30 to 70 sec, respectively). The conditions of atomic emission determination of normalized elements were studied. Analytical lines were selected taking into account the maximum intensity in the absence of spectral overlaps. The advantage of using the method of internal standard and the method of multidimensional calibration of the spectrometer is shown. Calibration of the spectrometer was carried out using monolithic standard samples of copper alloys. The accuracy of determination of the elements in copper alloys was proved in analysis of standard samples and comparative analysis of the obtained results and data obtained by recommended GOST methods. Statistical processing of the measurement results by the Student criterion did not reveal systematic errors. The results of the determinations obtained by the developed method show that rational combination of spark sampling and ICP-AES analysis provided high precision of rapid (duration of analysis is reduced to 30 minutes) and cost-effective determination without a necessity of using chemical reagents.