Relative Error Of Determination Research Articles

DEVELOPMENT AND VALIDATION OF SPECTROPHOTOMETRIC METHODS FOR DETERMINING SOME PROTON PUMP INHIBITORS

The study is devoted to the development and validation of methods for the spectrophotometric analysis of omeprazole and esomeprazole in the substance and various drugs. 96% ethyl alcohol was chosen as the general solvent. The operating wavelengths are 295 nm. The relative error of determination is ± 1.2% for “Omeprazole” capsules, ± 0.51% for “Omegast” capsules, ± 0.39% for “Esom” capsules, ± 0.32%. Validation of methods for the quantitative determination of omeprazole and esomeprazole in standard samples was carried out taking into account parameters such as specificity, linearity and accuracy.

Development and validation of method of quantitative determination of flavonoids from the above-ground part of Glycyrrhiza glabra L.

The aim of this study was to determine the optimal extraction factors of flavonoids from the above-ground part of licorice (Glycyrrhiza glabra L.) and to develop a method for their quantitative determination by differ-ential spectrophotometry. The object of the study was collected in the Volgograd region during flowering and dried samples of the herb of the medicinal plant. Ethyl alcohol 70% was chosen as the optimal extractant of flavonoids from the studied raw materials. It was found that the extraction of the maximum amount of flavonoid fraction is observed at three times extraction of plant raw material for 30 minutes each in the ratio with extractant 1:30. Quantitative determination of flavonoid compounds was performed by measuring the optical density of coloured complexes formed in extracts from the above-ground part of G. glabra L. with 2.5% aluminum chloride solution. Detection of the optical density of the tested solutions was conducted at a wave-length of 408 nm, corresponding to the maximum of the standard sample solution of rutin (Sigma, USA) after the addition of 2.5% aluminum chloride solution. Determined by differential spectrophotometry method the content of the sum of flavonoids in recalculation on rutin in extracts from the studied samples of plant raw materials of G. glabra L., obtained under the selected conditions, is 4.34±0.06%. The relative error of determination did not exceed 5%. A validation analysis was also conducted, the results of which showed the specificity, linearity and precision of the developed methodology. The studied validation parameters were within the acceptance criteria.

Спектрофотометрическое определение некоторых β-лактамных антибиотиков в их бинарных смесях с использованием метода проекций на латентные структуры

The method has been proposed for the spectrophotometric determination of antibiotics of the cephalosporin (cefuroxime, ceftriaxone, cefotaxime, cefazolin) and penicillin (amoxicillin) groups using chemometric data processing (method of partial least squares, PLS). The absorption spectra of 24 binary mixtures of “cephalosporin – cephalosporin” and 16 binary mixtures of “cephalosporin – amoxicillin” with various concentrations in the range of 3–27 and 5–140 μg/ml have been recorded. The optimal number of latent variables for each chemometric method (PLS-1 and PLS-2) has been selected, which ranged from 2 to 7 depending on the type of model and the nature of the antibiotics. The smallest root mean square calibration errors (RMSEC) have been found for the ceftriaxone–cefazolin system, which have been 0.09 and 0.08 for PLS-1 and PLS-2, respectively. The smallest root mean square errors of prediction (RMSEP) for the mixture “cefuroxime – amoxicillin” have been 0.07 for both methods (PLS-1 and PLS-2). It has been established that equations of linear relationships “measured-predicted” are characterized by a regression coefficient and the square of the approximation coefficient close to 1; which indicates the high quality of the models. The relative error of determination in test mixtures has been 0.4–6.2% by the PLS-1 method for “cephalosporin – cephalosporin” mixtures, and 0.07–6.0% by the PLS-2 method. At the same time, there is no significant difference in the error in determining the components of the mixture, in contrast to the “cefuroxime – amoxicillin” system, for which the error is 0.1–1.1% for the first component and 2.6–14.7% for the second component using the PLS-1 method and 0.2–1.2% for the first component and 4.3–13.3% for the second component using the PLS-2 method. Thus, it has been shown that the use of chemometric methods ensures high accuracy of the spectrophotometric determination of the studied antibiotics with overlapping absorption bands in their mixtures.

ПРИМЕНЕНИЕ МЕТОДА СПЕКТРОФОТОМЕТРИИ ДЛЯ КОЛИЧЕСТВЕННОГО АНАЛИЗА АТАЗАНАВИРА

HIV infection is currently a big problem in medicine and pharmacy. For therapy, antiretroviral drugs are offered, the range of which is constantly increasing. One such drug is atazanavir. When treating, it is very important to create the optimal dosage, which is based on the quantitative content of the substance. For the quantitative determination of the content of atanazavir, the regulatory documentation suggests the method of high-performance liquid chromatography (HPLC). The HPLC method, in addition to its advantages, also has disadvantages in the form of expensive and complex equipment and the need for standard USP samples. In this article, a unified method has been developed that allows to determine the quantitative content of atazanavir in the substance and capsules using the spectrophotometry method using external optical reference samples. Potassium ferricyanide is proposed as an external sample. The optimal conditions for determination are substantiated: solvents - 0.1 M hydrochloric acid solution and ethyl alcohol 95%, analytical wavelength - 302 nm. Conversion factors are determined, calibration graphs are presented. The relative error of determination according to the developed method for the substance was no more than 0.68%, for capsules - no more than 1.32%.

SPECTROPHOTOMETRIC DETERMINATION OF TAMSULOZIN IN REFERENCE SAMPLES AND DRUGS, VALIDATION OF METHODS

The article presents the results of quantitative spectrophotometric determination of tamsulosin in a standard sample, in “Tulosin” and “Ornadex” capsules using 96% ethyl alcohol as a solvent. The relative error of determination is ±0.25% for the standard sample of tamsulosin, ±0.93% for “Tulosin” capsules, ±1.43% for “Ornadex” capsules. The proposed method of quantitative determination was validated according to the specified parameters: specificity, linearity, and accuracy. When determining the linearity of the method, the concentration of 0.4-1.6 mg was determined as the working interval of the standard sample of tamsulosin hydrochloride (r=0.994). When determining the accuracy, it was found that the working solutions prepared in 96% ethanol do not change the optical density at the absorption maxima in a short period of time (RSD = 0.622). When determining the specificity, it was found that the excipients do not interfere with the analysis.

РАЗРАБОТКА И ВАЛИДАЦИЯ СПЕКТРОФОТОМЕТРИЧЕСКОЙ МЕТОДИКИ ОПРЕДЕЛЕНИЯ СОДЕРЖАНИЯ ФЛАВОНОИДОВ В ПУПАВКИ КРАСИЛЬНОЙ ТРАВЕ

The aim of this work is development and validation of a spectrophotometric technique for quantification of total flavonoids in terms of rutin in potentially medicinal plant Anthemis tinctoria herb. According to the literature, Anthemis tinctoria is used in folk medicine as a hepatoprotective, hemostatic and means, and its extracts in the experiment exhibit antimicrobial, cytostatic and antioxidant activities. In this work, we used sample of Anthemis tinctoria herb harvested in the summer of 2021 during the period of mass flowering in vicinity of Perm city (valley of the Vasilievka river, Adishchevo railway station). The raw materials were dried at room temperature, with sufficient ventilation, without direct exposure to sunlight, stored separately from other types of raw materials. According to the experiments the optimal conditions for determining of total flavonoids: grinding the raw material to a size passing through a sieve with a diameter of 1 mm, the optimal concentration of ethyl alcohol extractant is 50%, the analytical wavelength is 410 nm, the extraction time in a boiling water bath is 45 minutes, the ratio of extraction and complexing agent - 2% alcohol solution of aluminum chloride - 2:5. The technique was validated in accordance with the requirements of State Pharmacopeia of Russia 14th edition, the relative error of determination with a reliable probability of 95% was 4.00%. The technique can be used in further work to conduct studies of biological activity.

Determination of sarin and soman in industrial emissions by gas-chromatographic method using pulsating flame-photometric detector

Methods of gas chromatographic determination of trace amounts of sarin and soman in industrial emissions at a level of 1.0 × 10–6 mg/m3 have been developed. The capture and concentration of the target analyte was carried out using a specially designed sampling fluoroplastic cartridge filled with a pre-prepared sorbent Tenax TA with a grain size of 60/80 mesh and a volume of 8 cm3. The extraction of concentrated substances from the sampling cartridge was carried out using a modified and improved method of thermal desorption which consists in involving hot vapors of the solvent (resulted from the introduction of a liquid solvent into the cavity of the sampling cartridge with subsequent heating to 200°C) into desorption process in addition to the inert carrier gas. The substantially higher efficiency of the modified method of thermal desorption compared to the classical methods of extracting target substances from sorbents has been experimentally proved. Data on the quantitative content of sarin and soman were obtained by gas chromatographic method using a Varian CP-3800 gas chromatograph equipped with a pulsating flame-photometric detector, the mixture was separated on a VF-5ms capillary column. The sensitivity of a classical flame photometric detector and a pulsed flame photometric detector to sarin and soman has been studied. The developed methods have a relative error of determination about 27 %, and the duration of analysis of one sample is 3 h 30 min. The methods were tested on the real objects of control, appropriately certified and implemented in practice.

Precision of determination of thawing depth of the frozen rocks

An important quantity determining the choice of technical solutions in design of both surface and underground structures in the permafrost area is the thawing depth of the rocks. To obtain simple analytical relations to determine the thawing depth over time, a simple assumption is used: that the initial temperature of the rocks is equal to the melting temperature of ice. The aim of the present work was the assessment of impact of this assumption on the forecast precision. For a quantitative assessment, a simple typical formula recommended by construction norms was used. Functional dependence of the density of the rocks and their heat capacity on the fraction of ice content was considered in the formulas. A rock consisting of a combination of quartz sand and ice was used as an example.Multiple variant calculations were done according to the formulas and their results presented in the form of charts. It was shown that the relative error in determination of thawing depth depends solely on the Stefan criterion and is independent of the thawing duration, thermal conductivity coefficient of the thawing rocks and the air temperature during the thawing. A relation was obtained which allows to quickly assess at which initial values (temperature and ice content of the frozen rocks) it is possible to use the formulas obtained from the simplified calculation models with the assumption that the temperature of the rocks is equal to the melting temperature of ice.

Anion exchange extraction of tallium (III) and mercury (II) complex salts and application of the procedure to extraction-photometric determination of the microquantities of mercury (II)

The goal is to study the anion-exchange extraction of complex thallium (III) and mercury (II) halides (chlorides, bromides, iodides) by a method of a competing intermediate ion using the anions of various dyes — methyl orange, sodium picrate, 2,4-dinitrophenol, methyl red. Mercury (II) and thallium (III) are poisons of high toxicity. The developed method was used to study the anion-exchange extraction of acidocomplexes A solution of methyl orange trinonyloctadecylammonium (TNODA) in toluene was used as an extractant. The method provides determination of mercury (II) with an accuracy of ±2% when the concentration in the initial solution ranges within 2 – 8 × 10–8 mol/liter. It is shown that the values of the exchange constants for the same metal are larger for iodide complexes than for bromide and chloride ones. The extractability of metal halide complexes is mainly determined by their mass. Anions with a large mass have a large surface area, a low charge density, and are weakly hydrated, and thus are better extracted. The results of anion-exchange extraction were used to develop a procedure for the extraction-photometric determination of mercury (II) in granosan (ethylmercury chloride a prohibited insectofungicide of the 1st hazard class) the illegal use and storage of which could be a source of mercury pollution of groundwater in a number of regions of the Republic of Belarus. The relative error of determination does not exceed ±2%.

Spectrophotometric determination of bromate with 2-bromo-N,N-dimethylaniline

International Association for Cancer Research included bromates in the group of carcinogenic chemicals. Therefore, it is important to determine the content of bromates in different objects. The purpose of this study is to develop a simple, express and sensitive method for the determination of bromates. We propose the method of spectrophotometric determination of bromate in the concentration range of 0.5 to 45 mg L–1, this technique being based on the reaction of bromate with 2-bromo-N,N-dimethylaniline in the presence of an excess of KBr in the medium of sulfuric acid, followed by photometry of 2,4-dibromo-N,N-dimethylaniline at 240 nm. The optimal concentrations of reagents are determined and the influence of some other conditions on the sensitivity of determination is established. The detection limit of bromate (in compliance with 3s-criterion) is 0.39 mg L–1. The relative error of determination does not exceed 0.10. The influence of foreign ions is studied when determining bromate (5.010–5 mol L–1). Such components of natural water as phosphates, fluorides, chlorides and NH4+ ions have no effect on the bromide determination. Fe3+ ions in comparable quantities impede the determination of bromates. The developed method was tested for the determination of bromate in standard solutions and waters of different categories. The used reagents are stable over time and the proposed method is simple and suitable as an alternative for the determination of bromates in different objects.

Estimation of the height of the turbulent mixing layer from data of Doppler lidar measurements using conical scanning by a probe beam

Abstract. A method is proposed for determining the height of the turbulent mixing layer on the basis of the vertical profiles of the dissipation rate of turbulent energy, which is estimated from lidar measurements of the radial wind velocity using conical scanning by a probe beam around the vertical axis. The accuracy of the proposed method is discussed in detail. It is shown that for the estimation of the mixing layer height (MLH) with the acceptable relative error not exceeding 20 %, the signal-to-noise ratio should be no less than −16 dB, when the relative error of lidar estimation of the dissipation rate does not exceed 30 %. The method was tested in a 6 d experiment in which the wind velocity turbulence was estimated in smog conditions due to forest fires in Siberia in summer 2019. The results of the experiment reveal that the relative error of determination of the MLH time series obtained by this method does not exceed 10 % in the period of turbulence development. The estimates of the turbulent mixing layer height by the proposed method are in a qualitative agreement with the MLH estimated from the distributions of the Richardson number in height and time obtained during the comparison experiment in spring 2020.

Мультисенсорные системы типа «электронный язык» для раздельного определения цефотаксима и цефазолина

Electroanalytical properties of unmodified and modified by polyaniline and by CuO nanoparticles solid-contact potentiometric sensors which are based on associates of tetradecylammonium with complex compounds of silver (I) with cephuroxime, cephotaxime and cephazoline Ag(β-lac)2TDA in solutions of corresponding antibiotics were studied. It was revealed that Ag(β-lac)2TDA –based sensors had no specificity to the basic ion but showed sensitivity to other cephalosporins. Taking into account the potentiometric selectivity coefficients and cross-sensitivity parameters of sensors based on different electrode-active components, their use for creating «electronic tongue» multi-sensor systems was shown. Arrays of low-selective potentiometric sensors were created for separate determination of cephazoline and cephotaxime in two-component model mixtures at concentration intervals of 2,5·10-4 – 0,01 М. The method of artificial neural networks was used for processing analytical signals (the relative error of determination not exceeding 13%).

Multisensory Systems Based on Nafion Membranes Modified by PEDOT for the Determination of Sulfacetamide in Aqueous Solutions and Pharmaceuticals

Composite membrane materials based on Nafion-117 gradient modified by poly(3,4-ethylenedioxythiophene) (PEDOT) are prepared by in situ oxidative polymerization. 0.002 M and 0.01 M solutions of the monomer are used for the synthesis of PEDOT, while the concentration of the oxidant is varied. The equilibrium (water uptake, ion exchange capacity) and transport properties (conductivity, diffusion permeability, coefficient of diffusion) of membranes in the H+- and K+-forms are investigated. The influence of the modification of membranes on the characteristics of cross-sensitive Donnan potential (DP) sensors in the aqueous solutions containing sulfacetamide and an alkali in a wide range of values of pH (5.8–11.2) is studied. The array of cross-sensitive DP-sensors based on membranes with different compositions is used to determine the active substance in “Sul’fatsil natriya” pharmaceuticals from various manufacturers. The relative error of determination is 0.5–3%.

Potentiometric Sensors Based on MF-4SC Membranes and Carbon Nanotubes for the Determination of Nicotinic Acid in Aqueous Solutions and Pharmaceuticals

Perfluorosulfonic acid membranes MF-4SC with a uniform and gradient distribution of multi-walled carbon nanotubes (CNTs) along the length of the samples have been synthesized. The effect of the presence and concentration of CNTs in the membranes on the equilibrium and transport properties of materials has been studied. The cross sensitivity of Donnan potential (DP) sensors to nicotinic acid, sodium, and hydroxonium ions for membranes of different compositions has been determined. The incorporation of 0.5–1.0 wt. % CNTs into a membrane has led to a decrease in the detection limits of nicotinic acid ions in aqueous solutions by a factor of 2–3. An array of cross-sensitive DP-sensor based on MF-4SK and MF-4SC + 1.0 wt. % CNT membranes has been used to determine the active and auxiliary substances in a pharmaceutical based on nicotinic acid. The relative error of determination is 1.9%.

Application of a Pyrometer and Standard Sample to Determine The Surface Temperature of Materials Under Study

The methodology of determining the surface temperature of composite materials with unknown emissivity is studied. The methodology is implemented by using a standard sample of spectral normal emissivity over the range of wavelengths 1.65–1.80 μm and the industrially produced Metis M322 pyrometer functioning in the same range. The surface temperatures of the composite material under study and platinum, with significantly different values of spectral normal emissivity is determined by the temperature of the standard sample mounted on the materials under study, as measured by the pyrometer. The relative methodological error of determination of the surface temperature of materials under study did not exceed 1.7 and 0.5%, respectively, for the composite material and platinum for surface temperatures approximately 973 K. In the calculation of the error, the results of measuring the surface temperatures of the materials under study were used, obtained taking into account the temperature of the standard sample and in the absence of a standard sample. The imprecision of a priori data regarding emissivity of a standard sample in the interval (–0.01; 0.01) relative to the mean emissivity, equal to 0.19, increases the relative error of determination of the temperature of the composite material by 0.68%. Installation of a standard sample on the materials under study results in temperature modifications on the periphery of the surface, not exceeding 0.47 and 0.05%, respectively, for the composite material and platinum.

Atomic absorption determination of mercury in urine by cold steam method using mercury- hydride prefix

Mercury is one of the most common in various industries and at the same time dangerous chemicals. It is able to be deposited in the body and have a toxic effect for a long time after the cessation of contact. Under the influence of mercury, workers can develop various intoxications, as a result of which pathological changes in the nervous, cardiovascular, endocrine, immune and reproductive systems are possible.Under production conditions, mercury enters the body, usually in the form of vapors (absorbed about 80%) and suspended particles. Inorganic forms of mercury are excreted mainly in the urine (60%). However, insufficient attention is currently being paid to the problem of determining the mercury content in urine samples. To date, in world practice there is no systematic approach to the determination of small doses of mercury in the body, as a result of which it is difficult to timely identify public health disorders. This is largely due to the lack of highly sensitive and highly effective methods of analysis, allowing routine measurements with minimal cost and high accuracy. The methods currently used are either quite expensive or have low accuracy/sensitivity.The aim of the study was to develop a method of atomic absorption determination of mercury in urine by cold steam, which would allow at minimal cost to increase the accuracy and sensitivity of mercury detection in the body.Materials and methods. Quantitative measurement of mercury in urine samples was carried out on an atomic absorption spectrometer with a mercury-hydride prefix using model solutions of different concentrations.Results. The study determined the optimal conditions for sample preparation of urine samples, set the range of concentrations for the construction of the calibration schedule, studied the effect of the matrix on the accuracy of the analysis by the “introduced-found” method. The lower limit of detection of the developed technique was 0.05 mcg/l, the upper limit–100 mcg/l (if necessary, it can be increased by additional dilution). The relative error of determination depending on the concentration varied from 3 to 15%.Conclusions. A highly sensitive, affordable and relatively inexpensive method for the determination of mercury in urine has been developed, which will allow to diagnose with high accuracy the background contents of mercury in urine, which is especially important when inspecting workers of industries associated with the use of mercury and its compounds, as well as the population living in areas close to these industries.

Machine learning for predicting properties of porous media from 2d X-ray images

In this paper, Convolutional Neural Networks (CNNs) are trained to rapidly estimate several physical properties of porous media using micro-computed tomography (micro-CT) X-ray images as input data. The tomograms of three different sandstone types are subdivided to create a dataset consisting of 5,262 training images and 2,000 testing images. Porosity, specific surface area, and average pore size of each image are computed. The proposed CNN framework is trained with binary images and greyscale images separately and the corresponding computed properties. The results from testing the model are promising as the relative error in determination of porosity, surface area and average pore size is less than 6% when the model is trained with binary images and less than 7% when greyscale images are used. Other aspects related to model training and optimisation are discussed.

Design, modelling and construction of a continuous nuclear gauge for measuring the fluid levels

In this paper, we report on design, modelling and construction of a simple continuous nuclear gauge for measuring the fluid levels in vessels. In this instrument, a point source and a point detector are used on top and bottom sides of the vessel. The theoretical framework that is needed for analyzing the instrument data is described and it is shown that with this type of design, any unknown systematic error during the measurements can be removed. The developed theoretical relations and the instrument modelling by the MCNPX code, demonstrate its linear response in the entire measuring span. By using a cesium-137 gamma radiation source and a NaI (Tl) scintillation detector in the construction of the nuclear level gauge, the linear response of the instrument is also experimentally confirmed. It is shown that the mean relative error in determination of water level in the entire range of an 85 cm height vessel was less than 3.57%, which is reasonably acceptable for this simple design.

Modelling the loading of the nose-free cutting edges of face mill with a spiral-stepped arrangement of inserts

A mathematical model of loading of the nose-free cutting edges of each insert of the face mill with a spiral-stepped cutting scheme was created. It was established that the size of the cut elements depends on the feed magnitude, the design parameters of the mill and the position of inserts on the contact arc. Variable factors of simulation included the feed magnitude, the clearance angle of the inserts and slope angles of the cutter assemblies. This made it possible to determine the chip thickness and width of cut, the depth of cut, the maximum value of the main cutting edge angle and the cut area at an arbitrary position of the face mill on the contact arc. Simulation in the SolidWorks Motion environment has confirmed reliability of mathematical modeling of loading of the cutting edges of the mill. The relative error in determination of the cut area was in the range from 1.8 % to 5.7 %. Calculation of the cut elements in the arbitrary position of the cutter insert on the contact arc was made in the Maple environment. Analysis of influence of the design parameters of the cutter and the magnitude of feed on the values of the cut elements was made. It has been established that an increase in feed caused a linear increase in the chip thickness and width of cut and the depth of cut for the inserts of all steps. Optimal values of the clearance angle of the mill inserts (16°) and slope of the cutting assemblies (6°) were determined for the milling depth of 3 mm. Recommendations on the choice of rational values of design parameters of the face mill for its effective operation at various depths of cut were given. Thus, there are grounds to assert the possibility of improving productivity of machining flat surfaces at a required quality due to the use of nose-free face mills with a spiral-stepped cutting scheme.

Studies on reaction of reduced lipoic acid with Mukaiyama reagent and its application for pharmaceutical and food analysis

ABSTRACTA new sensitive method for the determination of lipoic acid (LA) in selected food items based on its reaction with Mukaiyama reagent (2-chloro-1-methylpyridinium iodide, CMPI) was developed. It was stated that CMPI reacts with reduced form of lipoic acid (dihydrolipoic acid, DHLA) and the stable product is produced. The spectrum of the labeled form of DHLA exhibits new band at 312 nm. Based on its spectral characteristics new spectrophotometric and UV–high-performance liquid chromatography (HPLC) methods of LA determination were elaborated. Both methods allowed determination of the analyte in the concentration range of 5 × 10−6–1 × 10−4 mol L−1 with limit of detection 0.39 × 10−6 and 0.77 × 10−6 mol L−1 for spectrophotometric and HPLC method, respectively. The practical usability of newly developed methods was checked by determination of lipoic acid contents in its pharmaceutical preparate Revitanerw. The proposed method was precise and accurate. The relative error of determination did not exceed ±0.067%. As chromatographic method allowed the determination of analyte in the presence of complex matrix, it was applied for assay of free fraction of α-lipoic acid in selected food items. A procedure of LA isolation from biological matrix was developed. The extraction with dichloromethane allowed quantitative recovery at 102.94 ± 4.20%. The green barley appeared to be the richest source of LA.