Scattering of chromatographic peak areas is the main source of the uncertainty of chromatographic quantitation. Scattering is attribured to several factors but non-con-trolled partial losses of the samples injected into chromatographic column is the most important reason among them. However, it is shown that peak areas of the same components (including the solvent) of the same samples correlate well with each other, which gives ground for replacing the absolute peak areas of target analytes by their ratios to peak areas of additional (other than internal) standards, e.g., solvents contained in the samples can be used as additional standards, due to the absence of principal restrictions on their chemical nature. The advantages of the procedure are considered on the example of the method of internal standard. Similar aproach can be used in the methods of standard addition and absolute calibration. The uncertainty of the results (the ratio of the variation coefficients of the absolute and relative peak areas) decreases 5-30 times depending on the scatter of peak areas determined experimentally.

We report on a cholesterol electrochemical behavior on chemically modified carbon-containing electrode. All the experiments are carried out on a voltammetric workstation. The dependence of the cholesterol electrooxidation signal on pH, electrochemical concentration (potential and time) and scan rate is demonstrated. Working conditions (pH = 6.86, v = 40 mV/sec) of cholesterol determination in model media are specified. The linear dependence ofcholesterol electrooxidation current at a potential of +1.06 V on the cholesterol concentration is observed up to 50 pmol/dm³. The detection limit is 0.07 pmol/dm³. Results of comparative determination of cholesterol in food using voltammetric and spectrophotometric procedures are presented.

An approach to studying the composition of synthesized zinc-based thin films doped with In and Ga using local X-ray spectrometry (LXS) and inductively coupled plasma mass spectrometry (ICP-MS) is developed. The dependence ofthe content and distribution ofthe additives in a sample on conditions of synthesis on rotating substrates is derived. The results of ICP-MS determination of predominant impurities in the solutions of films are used for validation of the results obtained by LXS without sample preparation. It is shown that dopant impurities at a level of less than 1 % at. may be determined only using inductively coupled plasma mass spectrometry.

A possibility of using carbon nanotubes (CNT) (obtained at different temperatures of synthesis and functionalized in oxidative treatment with concentrated HNO₃) for extraction of toxic elements from aqueous media and their subsequent determination is studied. Sorption of Be, Bi, Cd, Cr, and Pb ions from aqueous solutions is studied as a function of their concentration, pH of the solution, temperature and modification time and compared with the same sorption characteristics of activated carbon. Optimal conditions of preconcentration are specified for further analysis of the concentrate both as a solid phase isolated from the column (using arc atomic emission spectroscopy (AES)) and as an eluate (using atomic absorption analysis (AAA)). The determination limits at a preconcentration coefficient C_conc = 300 range within 1 X 10⁸ - 3 X 10⁷ % wt. (AES) and 0.1- 0.5 ng/ml (AAA), respectively. Accuracy of the determinations is proved in spiking tests and by comparison of AAA and AES data. The obtained results can be used in the analysis and purification of different process media and for environmental protection as well.

The results of studying operational properties of T15K6 hard alloy subjected to heat treatment in salt baths of different composition are presented. Heating temperatures of quenching (both in I20 oil and in air)and tempering are 1050 ± 100 and 400 ± 200 °C, respectively. Cutters with quick-change carbide inserts and rods (GOST 3882-74) are used in the experiments. Vickers hardness, cutting-induced wear, fine structure parameters, microstructure and surface fracture of the alloy are studied as a function of heat treatment modes. The microstructure of the material after heat treatment is studied on a μVizo-MET-221 metallographic microvisor and Jeol JCM-6000 scanning electron microscope. Tensile strength is determined in bend tests of carbide rods on a IR 5047-50-10 universal tension testing machine. Analysis of the degree of structure imperfection, stress state of the carbide phase and determination of phase composition is performed using an MD-10 microdiffractometer.

Dispergation conditions of zirconia doped with 3 % mol yttrium oxide are specified. Grain-size distribution of the power particles is determined using static laser scattering and optical microscopy. Electrophoresis with titration is used for measuring the dependence of zeta-potential of zirconia suspension on öl value. The effect of the acidity on the stability of suspension during measurement is considered. It is shown that stable suspension can be obtained by shifting pH value of dispersion media both to acidic or alkali regions and also by adding surface active substances (e.g., Dolapix CE 64).

The use of the methods of powder metallurgy (PM) appeared promising in manufacturing core pieces and electromagnets working in medium and strong static magnetic fields thus significantly improving the efficiency of production of magnetic circuits of electrical machines made of soft magnetic powder materials. One of the problems attributed to assessing the quality of soft magnetic powder materials consists in the lack of reliable methods for measuring the magnetic properties of materials obtained by PM-technology. We propose a method for measuring the basic magnetization curve B (H ), magnetic hysteresis loop, as well as magnetic parameters of powder materials (initial Ціп and maximum Цm_ax magnetic permeability, remanence B_r and coercivity H_c ). The method is advantageous for the possibility of real-time measurements of multi-stage changes of the magnetic flux (using electronic microwebermeter F-191). Coercivity force H_c is determined using extrapolation of the dependence of the width of the hysteresis loop for ring samples on the value of maximum magnetizing field. Measurements are carried out at successively increasing magnetizing field. The tested method of measurements provide determination of the magnetic properties of powder samples and features of formation of the magnetic properties of Fe-P powder soft magnetic materials attributed to the prehistory of their production which results in the porosity and defect structure of the material.

A general method for determination of the chemical composition of multicomponent phase in equilibrium solid-phase mixtures without their isolation is developed. The method is based on the dependence of any of intensive or extensive characteristics of the system (accompanying signal: reflection intensities, lines of Raman and IR spectra, thermal effects, etc.) on the composition of test samples of the system under study. For example, to determine the unknown phase X (A_xB_yC_z, wherein 0 ≤ x ≤ y, z, x + y + z ≤ 1, and z = 1- x - y) of a ternary (three-component) system, it suffices to prepare three equilibrium samples P - A_pB_fC_1-p-f, Q - A_qB_gC_1-q-g, and R - A_rB_hC_1-r-h . The intensity of the signal accompanying the reaction in sample P: p^A +f^B +⁽1 -p -f)C → a⁽A_xB_yC_1-x-y + I_p) +⁽p - ax)A + (f- ay^)B is I_p = aI. Expressions for I_q and I_r follow from the reaction equations in samples Q and R. Solution of the system of the equations thus obtained provides determination of the unknown values x, y, and z. Thus, for n-component systems it is necessary to prepare n samples, measure the intensity of accompanying signal for each sample and carry out similar calculations.

A method of mathematical processing and algorithm of numerical adjustment of experimental fields of displacements on a specimen surface in the vicinity of the crack tip is proposed taking into account displacement of the body as a rigid unit upon loading and actual position of the crack tip. The initial experimental displacement fields around the tip of the fatigue crack in a compact specimen are determined by the method of digital image correlation. Taking a compact specimen as an example we demonstrate the possibility of successful using of this approach to obtain the distribution of the stress intensity factors and nonsingular Г-stresses along the front of a spatial crack.

Fibre sensing elements based on Bragg gratings (FBG) form a promising basis for developing sensors used for determination of the deformation in measuring systems, in particular, for built-in control of different designs. A possibility of their use in the structure of polymeric composite material intended for aircraft industry. The operation principle of the FBG is based on a change of the lattice constant - periodic structure of the refractive index of the optic fiber core - which can intail also thermal expansion (compression) of the fiber. Therefore, bearing in mind the goal of built-in control, it is important to understand what is the reason for optical fiber deformation in the site of FBG location - mechanical loading or change in temperature conditions. We systematize different approaches to consideration of temperature changes occurred upon strain measurements using FBG and present the main results thus gained. Moreover, we describe possible pathways of implementing each approach, provide data on the accuracy of strain and temperature measurements and present a structural design of the sensor.

The effect of technological flow parameters on the stress-strain state of structural elements of wedge gate valves is considered in the case study of ZKL2 300-25 using ABAQUS software package. Numerical calculations are performed with allowance for the temperature of liquid (water, mazut and petrol) flowing through the valve in given range of the flow velocities. The main parameters affecting the life-time of the structural elements of valves are determined. An algorithm of integrated approach to evaluation of the durability of wedge gate valves is developed. The algorithm can be recommended for institutions developing design specifications and estimates regarding repair, reconstruction, expansion and technical re-equipment of hazardous industrial facilities.

A problem of determining direct and inverse static characteristics of the object with interference present is considered. It is shown that solution of the problem in the framework of the statistical approach often ignore the existence of various sources and triggers of model interferences, which leads to substantial distortion of the estimates of errors and formation of inadequate conversion response. The types and sources of errors in determination of the static characteristic and conditions under which the use of statistical approach is valid are considered.

A generalized energy criterion which makes possible to assess the potential quality of a measuring experiment and link the accuracy of the experiment (the lower boundary of the error estimate variance) and time of achieving the accuracy in a certain class of distributions of correlated monitoring noise is determined. The use of energy criterion is considered for measuring experiment conducted in a discrete or continuous observation time. It is shown that regardless of the time of the experiment the resulting expressions have internal unity. The expressions of the energy criterion are derived which provide correlation between the parameters of the measuring experiment: duration of measurements; time constant of correlated observation noise; conventional sig-nal-to-noise ratio and desired accuracy of measurements. The relations thus obtained can be used in theoretical and applied calculations if the correlation function of the monitoring noise exhibits exponential or close to exponential character.