New Method For Determination Research Articles

Разработка и валидация методики определения нового эффективного ингибитора вируса гриппа H1N1 в плазме крови

Разработана методика определения противовирусного агента в плазме крови методом ГХ/МС. Пробоподготовку проводили осаждением белков метанолом. Методика валидирована по следующим параметрам: селективность, линейность, правильность, прецизионность, предел количественного определения, перенос, стабильность. Аналитический диапазон методики составил 0,1 – 2 мкг/мл. Метод может быть применен при проведении фармакокинетических исследований.

Effect of Convection on Formation of Adsorbed Surfactant Film under Dynamic Change of Solution Surface Area

The dynamics of the formation of a surface phase in aqueous solutions of surfactants in a tray with the Langmuir barrier system during one compression–expansion cycle of the interface boundary is investigated both experimentally and theoretically. Organic salts of fatty acids such as potassium laurate, caprylate, and acetate, which are members of the same homologous series, were used as surfactants. It is experimentally determined that the dependence of the surface pressure increment measured under the maximum compression of the surface on the volume concentration has a maximum, the position of which is different for all the studied surfactant solutions. It is shown that the position of the maximum corresponds to the concentration value at which a saturated monolayer of surfactant molecules is formed at the interface boundary. A theoretical model that considers the effect of the forced convection arisen in the bulk of the solution upon changing the surface area is proposed for the interpretation of the experimental results. The model allows one to render the main kinetic characteristics of the adsorption/desorption processes involving the compounds under study. A good agreement between the theoretical and experimental results is observed, but there is a discrepancy between them when diffusion is considered to be the only way surfactant molecules are transferred into the bulk phase. Based on the data, a new method for determination of the Langmuir–Shishkovsky constant is proposed.

Structural and mechanical properties of hypereutectic AlSiFe powders and a new method for determination of sintering temperature

In this study, the effect of Si amount on the microstructure, crystal structure and some mechanical properties of Al-(20,25,30 wt%)Si–5Fe powder mixtures produced by high energy ball milling method was investigated by determining the sintering temperature. In the X-ray diffraction analysis, no inter-metallic phases were found except for the Al, Si and Fe phases of the powder mixtures. The X-ray diffraction patterns were analyzed by the Rietveld method to determine amounts of the Al, Si and Fe elements in the powder mixtures. From the scanning electron microscopy analysis, it is seen that as the amount of Si increases, there is a marked decrease in the grain size of powders. In the micro-indentation tests performed at room temperature, the hardness and elastic modulus values of the pelletized powders were found to increase with the amount of Si. It was also found that the Al-20Si-5Fe powder mixture with the lowest Si content had the highest damping capability. The high temperature micro-indentation tests showed that the resulting Al-(20,25,30 wt%) Si-5 Fe powder mixtures started to consolidation at 200 °C and completed the consolidation at 400 °C. This method can be used as an alternative method in the determination of the sintering temperature of materials.

A new method for determination of cocamidopropyl betaine synthesized from coconut oil through spectral shift of Eriochrome Black T

Cocamidopropyl betaine (CAPB) is a zwitterionic surfactant that is synthesized using coconut oil and usually supplied in form of an aqueous solution with 25–37% w/w. In this study, a novel method based on UV–visible spectroscopy is developed for an accurate determination of CAPB synthesized from coconut oil. Eriochrome Black T (EBT) as a specific color indicator was added to CAPB and a red shift and color change were observed. This shift leads in increasing wavelength selectivity of the method. The change in the color intensity depends on the concentration of CAPB. By measuring the absorbance of a solution containing CAPB, its concentration was measured. After optimizing all the effective parameters, CAPB was detected in commercial real samples. Using the proposed approach, limit of quantification (LOQ) and relative standard deviation (RSD) were obtained about 4.30×10−5M and 4.8% respectively. None of unreacted materials or by-products, which were produced in the synthesis of CAPB, showed any interference in the determination of CAPB. This shows that the proposed method is specific and accurate, and can potentially be used for quantitative determination of CAPB in commercial samples with satisfactory results.

Splitting tensile behavior of autoclaved aerated concrete: Comparison of different specimens’ results

This research presents results of the experimental and numerical study of Brazilian tests on cylindrical and cubic specimens made of autoclaved aerated concrete. Failure mechanisms are discussed based on spatial finite element simulations and experiments with the digital image correlation and strain gauges. The simulations have been carried out using the constitutive model of isotropic plasticity with the Mohr-Coulomb yield condition and the strain softening hypothesis. A new method of determining of elastic constants for the cylindrical specimen has been developed. The Young’s modulus and the Poisson’s ratio are determined by fitting the theoretical solutions into the displacement field obtained experimentally.

Investigation of heat and mass transfer processes by the method of structured laser radiation caustics

This paper is devoted to investigation of possibilities of using the caustic method for determination of optical inhomogeneities parameters, which arise by heat and mass transfer processes. Conditions of the caustics appearance are considered for longitudinal probing of the diffusion layer of liquid by plane and cylindrical laser beams. Experimental visualization of dynamics of change in the caustics position is presented for various parameters of inhomogeneous media. New method for determination of surface temperature of a cooled body placed in transparent liquid is described.

Differential pulse voltammetric determination of salbutamol sulfate in syrup pharmaceutical formulation using poly(4-amino-3-hydroxynaphthalene sulfonic acid) modified glassy carbon electrode

A new method for determination of salbutamol sulfate has been developed using poly(4-amino-3-hydroxynaphthalene sulfonic acid/GCE. Cyclic voltammetric investigation of the electrochemical behavior of salbutamol sulfate at the polymer modified glassy carbon unveiled electrocatalytic activity of the modifier towards irreversible oxidation of salbutamol sulfate. Dependence of peak current predominantly on scan rate than on square root of scan rate, and peak potential shift with pH demonstrated that oxidation of salbutamol sulfate at the polymer modified electrode follows adsorption reaction kinetics with proton participation.Under optimized solution and differential pulse voltammetric parameters, the oxidative peak current showed linear dependence on salbutamol sulfate concentration in the range 0.2 to 8 μM with method detection limit (3s/m) and determination coefficient (R2) of 6.8 × 10−8 M and 0.99786, respectively. Low method detection limit, relatively wide linear range, and recovery results of spiked standard salbutamol sulfate in syrup samples in the range 96.7–98.9% validated the method for determination of salbutamol sulfate in pharmaceutical formulations.Differential pulse voltammetric analysis of salbutamol sulfate syrup formulation for its salbutamol sulfate content revealed 98.8 to 99.3% of the labeled value confirming the applicability of the developed method for determination of salbutamol sulfate in real samples.

Development and comparison of chromatographic methods for the analysis of long chain diols and alkenones in biological materials and sediment

We have compared and assessed the suitability of several chromatographic methods for the analysis of long chain alkenones and long chain diols and the associated paleotemperature proxies (UK’37 and LDI). We evaluated the traditional methods for the analysis of the UK’37 and the LDI, gas chromatography (GC) − flame ionization detection (FID) and GC mass spectrometry (MS) using selected ion monitoring (SIM), respectively, and developed a new method using GC–MS/MS in multiple reaction monitoring mode (MRM) for the analysis of long chain diols as well as a method for automatic silylation of diols using a robot autosampler. Finally, we evaluated liquid chromatography (LC) methods to simultaneously measure the UK’37 and the LDI, using ultra high performance LC (UHPLC) with low (nominal mass) resolution MS in SIM mode, and UHPLC with high resolution MS (HRMS). Detection and quantification limits and reproducibility were assessed by means of serial dilutions of culture extracts.Automated silylation by a robot autosampler showed similar reproducibility as off-line silylation while substantially decreasing sample preparation time. The novel MRM method had a slightly lower limit of quantification (LOQ; i.e. 0.3pgC28 1,13-diol injected on-column) than the traditional method (0.5pg) and improved reproducibility while allowing more unambiguous identification of LCDs in complex matrices. For diols, UHPLC–MS using SIM had the highest LOQ (i.e. 15pg) and a comparable reproducibility as GC–MS. UHPLC–HRMS had a LOQ of ca. 1.5pg, and an improved reproducibility for diol analysis. For alkenone analysis, both UHPLC–HRMS and UHPLC–MS using SIM were 2–3 orders of magnitude more sensitive (LOQ ca. 20 and 2pgC37:2 alkenone injected on-column, respectively) than GC-FID (LOD ca. 3ng), with a similar reproducibility of the UK’37 index. Hence, UHPLC–HRMS allows simultaneous analysis of the UK’37 and LDI at an increased sensitivity. In addition, it allows simultaneous measurement of TEX86, a temperature proxy based on the isoprenoid glycerol dialkyl glycerol tetraethers. This reduces the preparation time by excluding the need of derivatization and separation of the ketone (containing the long chain alkenones) and polar fractions (containing the long chain diols and GDGTs). However, synthetic standards are required to fully assess the accuracy of the new methods for determination of the LDI and UK’37.

Determination of Caspase-3 Activity and Its Inhibition Constant by Combination of Fluorescence Correlation Spectroscopy with a Microwell Chip.

Caspase-3 is a key enzyme executing apoptosis during ontogenesis and homeostasis of multicellular organisms, and is a very important and potential drug target in treatment of apoptosis disturbance. So far, no commercial drugs for caspase-3 are available, and it is urgently necessitated to develop an effective method for caspase-3 activity assay and its inhibitor screening. In this paper, we propose a new method for determination of caspase-3 activity and its inhibition constant by combining single molecule fluorescence correlation spectroscopy (FCS) with a microwell chip. Its principle is based on measurement of the enzyme reaction kinetics and homogeneous detection of the reaction product by FCS. This system can reduce the requirement sample volume to 1 μL level. The caspase-3 substrates are doubly labeled with fluorophore and biotin, the enzyme reaction can be quickly terminated in the presence of streptavidin, and the reaction products can be selectively detected by FCS. We established the model of caspase-3 inhibitor screening by combining the dynamics of enzyme reaction with FCS theory. This new method was successfully used for determination of inhibition constants of certain inhibitors and assay of drug-induced apoptosis. Compared to current methods, this method shows high sensitivity, small reagent dosage and short analysis time. We believe that this method will become an efficient platform for screening of caspase-3 inhibitors and detection of apoptosis.

Analysis of the Methods of Determination of the Viscoelastic Coefficients of Piezoceramic Resonators

We analyze the well-known and new methods for the experimental determination of the viscoelastic coefficients of piezoceramic resonators including the coefficients of coupling and the tangents of mechanical and piezoelectric losses. The foundations of author’s new computation-experimental technique are outlined and the examples of its application are presented. The method is justified by using, as an example, the well-known problem of radial vibrations of a thin disk with continuous electrodes. The idea of alternating measurements of voltage drops in a modernized Mason circuit is developed. On its basis, we develop a new method for the determination of phase shifts between the components of admittance by the cosine theorem and present some elements of this technique. The experimental data are in good agreement with the numerical results.

A Method for Determination of the Minimal Thickness of the Cutting Layer during Precision Machining Performed with the Indexable Cutting Tools

Under the influence of the pressure caused by the application of the cutting edge on the surface of the workpiece elastic waves are generated. Waves propagate in the material in every possible direction and can be identify by specialized measuring equipment. Acoustic emission phenomenon was used to determine the beginning of decohesion process. The article presents a new method for determination of the decohesion process during peripheral milling performed with the indexable cutting tools on samples made out of titanium based alloy and nickel based alloy.

Is there any alternative to traditional food frequency questionnaire for evaluating habitual dietary intake?

Dietary assessment methods are an important instrument for nutrition research. Food frequency questionnaires (FFQs) have been the most frequently used dietary assessment tool in epidemiological and intervention studies. There is a great necessity for new methods of determination of habitual dietary intake that overcome the limitations of these traditional methods. The objectives of the present study were to develop a new method, based on an application for mobile phones called e-EPIDEMIOLOGY, designed to record individual consumption data about a short series of foods/drinks, and to compare data collected using this tool with those obtained from a previously validated short paper FFQ. University students over 18 years recorded the consumption of certain foods/drinks using e-EPIDEMIOLOGY during 28 consecutive days and then filled out a short paper FFQ at the end of the study period. To evaluate the agreement between both methods, Spearman's correlation coefficient, cross-classification analysis and a weighted kappa statistic were used. One hundred and nineteen participants completed the study (71.4% female and 28.6% male). The mean Spearman's correlation coefficients for food/drink group intake between the two methods was 0.73. The mean percentage of participants cross-classified into categories of "exact agreement + adjacent" was 91.6%. The average weighted kappa statistic was 0.60. The results indicate that e-EPIDEMIOLOGY has good agreement with the previously validated FFQ short paper. However, it was noted that further testing of e-EPIDEMIOLOGY is required to establish its wider utility.

Target tracking with fast adaptive revisit time based on steady state IMM filter

Time is a valuable resource in phased-array radar and proper use of it enables the radar to track more targets simultaneously. Appropriate usage of time in the tracking means the radar can minimize the revisit rate of the tracked targets while the accuracy of targets position estimation is still acceptable. In this paper, a new method for determination of target revisiting time is proposed which has relatively low computational cost and uses steady state filters with Interactive Multiple Models structure. The proposed algorithm allows the radar designer to determine the filter parameters by some criteria such as the desired accuracy and targets maneuver. The performance of the proposed method is compared with the conventional filters for standard maneuverable flying targets. Simulations show the better accuracy and reliability of the proposed method beside its less target revisit time and computational load.

Palladium-Catalyzed C–H Activation: Mass Spectrometric Approach to Reaction Kinetics in Solution

We report a new method for determination of rate constants of processes in solution using electrospray ionization mass spectrometry (ESI-MS). The investigated reaction is C–H activation of acetanilides by palladium(II)trifluoroacetate leading to stable organopalladium complexes. The rate constants can be determined from an experiment with a couple of differently substituted acetanilides being in competition for being activated by the palladium salt. The formed organopalladium complexes can be detected by ESI-MS. The time dependence is achieved by adding one of the acetanilides to the reaction mixture with a time delay. The kinetics can be then evaluated from the evolution of the ratio of the ESI-MS signals of differently substituted complexes as a function of the time delay. The Hammett analysis of the rate constants obtained for a series of meta- and para-substituted acetanilides provides a ρ value of −1.5, which is in agreement with values reported for similar C–H activations. We have also investigated ...

Development of a New Method for Determination of the Oil Content from Microalgae Lipid Fraction

The purpose of this study was to develop a method for rapid quantitative and qualitative determination of the oil from microalgae lipid fraction obtained from Nannochloris sp biomass. The lipid fraction was first refluxed with 4% KOH in MeOH (60, 90, 120 min), followed by reaction with 20% BF3 in MeOH, using different times of reflux (90,120, 150 min) for each time of reflux with 4% KOH in MeOH. The FAME samples were analyzed by GC-MS analysis. 120 min reflux with 4% KOH in MeOH, 90 min with 20% BF3 in MeOH and a ratio lipid fraction: 4% KOH in MeOH: 20% BF3 in MeOH=1:20:27, were required to obtain the higher percent of oil in the microalgae lipid fraction. The relevance of the method developed was proved by TGA analysis and by transesterification of a sunflower oil sample in the same conditions.

Generalized characteristic ratios assignment for commensurate fractional order systems with one zero

In this paper, a new method for determination of the desired characteristic equation and zero location of commensurate fractional order systems is presented. The concept of the characteristic ratio is extended for zero-including commensurate fractional order systems. The generalized version of characteristic ratios is defined such that the time-scaling property of characteristic ratios is also preserved. The monotonicity of the magnitude frequency response is employed to assign the generalized characteristic ratios for commensurate fractional order transfer functions with one zero. A simple pattern for characteristic ratios is proposed to reach a non-overshooting step response. Then, the proposed pattern is revisited to reach a low overshoot (say for example 2%) step response. Finally, zero-including controllers such as fractional order PI or lag (lead) controllers are designed using generalized characteristic ratios assignment method. Numerical simulations are provided to show the efficiency of the so designed controllers.

Carotid–Femoral Pulse Wave Velocity Assessed by Ultrasound: A Study with Echotracking Technology

Described here is a new method for determination of carotid–femoral pulse wave velocity (PWV) based on arterial diameter waveform recording by an ultrasound system. The study was carried out on 120 consecutive patients. Carotid–femoral PWV was determined using a tonometric technique (PWVpp, PulsePen, DiaTecne, Milan, Italy) and an echotracking ultrasound system (PWVet, E-Track, Aloka, Tokyo, Japan). The relationship between PWVpp and PWVet was evaluated by linear regression and Bland–Altman analysis. There was excellent agreement between PWVet and PWVpp (Pearson's r = 0.94, 95% confidence interval: 0.91–0.96, p < 0.0001; PWVet = 0.88 × PWVpp + 0.57). The Bland–Altman plot revealed an offset of −0.33 m/s with limits of agreement from −2.21 to 1.54 m/s. The coefficients of variation for within-subject repeatability between PWVet and PWVpp had were 5.79% and 8.47%, respectively, without significant differences in the Bland–Altman analysis. The results suggest that echotracking technology can provide a reliable estimate of aortic stiffness comparable to that of the tonometric techniques.

Modern modification of the method for determination of organochlorine pesticides in organic vehicles

New method for determination of organochlorine pesticides (DDT and its metabolites, HCH and its isomers) is presented. The method includes a liquid-liquid extraction of pesticides under ultrasound and the substance analysis by gas-liquid chromatography. The degree of DDT and γ-HCH extracting from tissues of marine organisms is (78 ± 2) % and (91 ± 2) %, respectively. The total content of organochlorine pesticides in muscles of walleye pollock from the Okhotsk Sea is evaluated by this method in the range from 25 to 73 pg/g of lipids.

Development of a new method for determination of infiltration coefficients in furrow irrigation with natural non-uniformity of slope

In this study, a new method was developed to calculate the infiltration coefficients in furrow irrigation with natural non-uniformity of longitudinal slope. For this purpose, 12 usual tilled furrows with 42 m length and 60 cm width were selected. Then, five irrigation events were carried out and the advance-recession and inflow-outflow data were collected. The parameters of the infiltration equation in power-polynomial form (Kostiakov–Lewis) were calculated using the volume-balance (VB) method and based on a power model as advance equation. The non-uniform longitudinal slope in furrows was purposefully made, so that the advance function should not to follow a usual power function, and the power of function to be more than one in some cases. Besides, in some irrigation events, the negative infiltration equation was obtained. Accordingly, from analysis of VB equation components, several modifications were incorporated in procedure of parameter estimation. Some of these modifications include fitting a quadratic function for advance data and calculating the flow cross-sectional area from maximum surface storage value. Volume of infiltrated water was calculated using this method in each irrigation, and compared with the measured volume based on the inflow and outflow hydrographs as a control. The results showed that using the presented method, the average error in computed infiltrated volumes was reduced to about 4%, which validates the application of the new method.

A New Method for Determination of Alfatoxin M1 in Milk by Ultrasensitive Time-Resolved Fluoroimmunoassay

A competitive indirect time-resolved fluoroimmunoassay (TRFIA) for detecting aflatoxin M1(AFM1) contamination in milk was developed, by using aflatoxin M1-bovineserum albumin conjugate, anti-AFM1 antibody, and Eu-labeled goat anti-rabbit antibody. To improve the sensitivity of the assay, the concentrations of the coating antigen and anti-AFM1 antibody were varied to optimize the condition of the immunological assay. The limit of detection values, limit of quantification values, and dynamic working range were 0.006, 0.022, and 0.022–1.334 μg/kg, respectively. Values of recovery within and between assays were 88.0–116.0% and 92.69–108.63%. The method was applicable for the full-cream, semi-skimmed, skimmed, and raw milk as well. Values of repeatability (intra-laboratory variability) and reproducibility (inter-laboratory variability) were 1.2–4.5% and 0.8–5.0%, respectively. The results of using AFM1-TRFIA to analyze samples of 23 brands of milk that were purchased in Wuxi revealed that AFM1 was absent from all studied samples. This study suggests that the novel method is a simple, sensitive, specific, reproducible, economic, and adequate method for screening large quantities of samples and has good prospects of application.