Standard Gravimetric Method Research Articles

English

Moisture sorption isotherms of Pleurotus ostreatus were determined at three different temperatures (10, 30 and 40) and relative humidity (6 to 88%), using standard static gravimetric method. The samples were used to determine the equilibrium moisture content and the data fitted to the Guggenheim-Anderson-de Boer (GAB) equation to describe the moisture adsorption characteristics within the water activity used for this study. Model parameters c, k and Mo were derived. The GAB monolayer moisture values (Mo) were 0.179, 0.163 and 0.123 at 10, 30 and 40°C respectively. The c and k value decreased from 0.729 to 0.613 at 10°C and 19.455 to 18.551 at 30°C, and increased to 0.712 and 24.737 when the temperature was further increased to 40°C. The mean relative percent modulus (%E) were 1.318, 5.393 and 3.224% at 10, 30 and 40°C respectively. The r2 values obtained varied between 0.980 and 0.997, indicating strong correlations between the experimental and predicted data; whereas the error values ranged from 0.007 to 0.017, showing very good fitness between the experimental moisture sorption and the modeled sorption. Thus, GAB model could be used to predict the moisture sorption behavior of P. ostreatus mushroom at the range of water activity used in this study. Key words: Pleurotus ostreatus, mushroom, Guggenheim-Anderson-de Boer (GAB) model, adsorption, isotherm, monolayer.

Assessment of influence of disperse filler polarity on structure and water absorption of epoxy compositions

Introduction. Composite materials on the basis of epoxy resin find wide application as adhesives, coatings and structural materials whose properties it is possible to regulate by introduction of various additives including disperse fillers in the epoxy binder. Positively influencing properties of epoxy materials, the disperse fillers can reduce water resistance of the materials. This work is aimed at studying of influence of polar and nonpolar disperse fillers on structure and water absorption of the epoxy materials. Materials and methods. When obtaining composite materials, the following components were used: ED-20 epoxy resin (state standard GOST 10587-84), dibutylphthalate (state standard GOST 8728-88) plasticizer, polyethylenepolyamine (specification TU 2413-357-00203447-99) hardener, marshallite (state standard GOST 9077-82) and graphite (state standard GOST 17022-81) disperse fillers. The structure of samples was investigated by means of IR-spectroscopy method. Water absorption was determined in boiling water using the standard gravimetric method (state standard GOST 4650-2014 (ISO 62:2008)) and evaluated by sample mass variation within 120 days. Results. As a result of the conducted researches, the optimum content of the marshallite and graphite fillers in epoxy materials is established. When mass filler-to-binder ratio is equal to 15/85, water absorption of the materials is minimum. The IR-spectroscopy method showed that introduction of the marshallite polar filler in the epoxy binder promotes ordering of material structure due to formation of hydrogen bond between reactive groups of the filler and resin. Localizing in amorphous areas, particles of the graphite nonpolar filler lead to weakening of the hydrogen-bond system. Interaction of marshallite-filled samples with water is accomplished at the swelling mode, with equilibrium degree of swelling about 1 %. The mechanism of interaction of graphite-filled samples with water includes the alternating stages of dissolution and swelling, which are more expressed as compared with check samples. Conclusions. Water resistance of epoxy materials filled with disperse fillers is defined by a microstructure of the cured resin. Introduction of the marshallite polar filler in the epoxy binder leads to ordering of material structure that results in increasing of water absorption. Introduction of the graphite nonpolar filler in the epoxy binder leads to disordering of material structure that results in reducing of water absorption. Lower value of water absorption of graphite-filled epoxy material is connected with partial dissolution of the sample. Using nonpolar fillers is inexpedient for epoxy materials contacting with water.

Moisture sorption isotherm of natural condiment cube made from juice water of katsuobushi plant, coated with edible coating and stored at ambient temperature

This research aimed to study the MSI of natural condiment cube coated with an edible coating, using the standard gravimetric method. Condiment pasta was performed into small cubes about 15 mm wide, dried, and coated with an edible coating made from carrageenan flour. Uncoated cube was used as a control sample. Samples of natural condiment cube were placed in a series of desiccators represented of a range of RH’s, and allowed to equilibrate, indicated by constant weight of samples. Water content of equilibrated sample was then measured as equilibrium moisture content (EMC). Five models of the equation were used in this experiment to fix Moisture sorption isotherm (MSI) data. The results show that natural condiment cube coated with edible coating has lower water content than control. The equilibrium moisture contents of natural condiment coated with edible coating ranged between 7.0 and 76 % dry basis. Henderson models showed best-fit values of regression coefficients with mean relative determination (MRD) of 8.21, and moisture sorption isotherm curved were sigmoid. In conclusion, edible coated were effectively used as a coating of natural condiment cube, stored in ambient temperatures only in RHs lower than 75%.

ADSORPTION ISOTHERMS OF KIWIFRUIT DRIED BY DIFFERENT DRYING METHODS

The aim of this study was to determine the moisture adsorption isotherms of kiwifruit dried by hot air, vacuum and freeze drying methods. Equilibrium moisture contents (EMC) of dried kiwifruits were obtained by using the standard gravimetric method at two different temperatures (25 and 45°C) within a range of water activities from 0.112 to 0.936. The adsorption isotherms of dried kiwifruits decreased with increasing temperature and exhibited type III behavior. Six different isotherm equations (GAB (Guggenheim-Anderson-de Boer), BET (Brunauer-Emmett-Teller), Oswin, Henderson, Halsey and Peleg) were employed to describe the experimental adsorption isotherm data. Adsorption data obtained at both 25 and 45°C for vacuum dried samples and data obtained at 45°C for hot air and freeze dried samples were best represented by Peleg equation. For the samples dried by hot air and freeze drying, GAB equation gave the best description of the experimental data obtained at 25°C.

Design and Characterization of a Fringing Field Capacitive Soil Moisture Sensor

This paper addresses the optimization and implementation of a fringing field capacitive soil moisture sensor using the printed circuit board technology. It includes the analysis of a novel configuration of an interdigital sensor for measuring soil moisture with two existing configurations. The optimized designs were simulated by using a 3-D finite-element method and fabricated by using a copper clad board. The performance of the fabricated sensors was evaluated using four soil samples collected from different locations. The observations were compared with the standard gravimetric method to evaluate the soil water content of the samples. The characterization method and the results of the whole sensing system are discussed in terms of calibration, dynamic test, and repeatability.

Determination of Desorption Isotherms of Potato Using Gravimetric Method and Fast Isotherm Method

The desorption isotherms of potato (Solanum tuberosum) were determined for a range of temperature 30–60 °C using gravimetric and fast isotherm method over the range of relative humidity 5–85%. The objective of this work is to investigate and document the best practice to perform experiments using both these two methods. The desorption isotherms obtained from the gravimetric method were fitted using three models: GAB, BET, and Oswin. A nonlinear least-square regression analysis was used to evaluate the constants of the three isotherm models. The goodness of the fit was determined by two statistical parameters: standard error and correlation coefficient. GAB model was found to be competent to describe desorption isotherms of potato followed by BET and Oswin model. Also, the sorption behavior of potato obtained from the fast isotherm method was validated to the standard gravimetric method.

Moisture Sorption Isotherm Modeling Approach and Effect of Packaging Material on Quality Changes in Extruded Product Stored Under Controlled Conditions

The aim of this study was to investigate the moisture sorption isotherms and the effect of storage on the quality of extruded snacks packed in low-density polythene and aluminium-laminated polythene at ambient (51 ± 1%, Relative humidity and 30 ± 1 °C, temperature) storage conditions. Moisture sorption isotherms were determined at temperature range 25–45 °C and relative humidity from 11 to 84% using the standard gravimetric static method. The experimental data were analyzed using five model equations such as GAB, Oswin, Smith, Caurie, and Halsey. The sorption isotherms for extruded product exhibited sigmoid curve of type II behavior and were found to be decreased with increasing temperature. The GAB, Oswin, Smith, and Caurie models were found to be the most suitable for describing the sorption curves. Storage stability in terms of quality parameters such as moisture content, lateral expansion, bulk density, hardness, color and sensory characteristics was assessed in both pouches. The extruded snack packed in low-density polythene pouches showed greater changes to quality parameters in comparison to aluminium-laminated pouches during storage. Therefore, it was suggested that aluminium-laminated pouches can store extruded product for a longer time period than low-density polythene pouches.

An Alternative Technique for Determining Gravimetric Particle Mass Deposition on Filter Substrate: The Particle Extraction Method

Airborne particulate matter (PM) filter sample processing is susceptible to error and can present issues associated with organizing samples, tracking data, and maintaining weighing conditions. While filter weighing facilities should implement robust quality assurance and control checks to ensure that data collection is accurate and filter storage is secure, mistakes and accidents can still occur that compromise valuable data. This paper presents a novel approach to PM filter sample processing that allows for data validation or data recovery while ensuring data integrity. The technique approximates the original, unused pre-sampling weight of polytetrafluoroethylene (PTFE) filters after PM collection to determine PM mass-deposition (MD). The method describes the extraction of PM loaded on PTFE filters via sonication in relatively non-toxic solvents, methanol and distilled water. The extraction method is compared to the standard gravimetric PM MD determination method for a set of 265 PTFE filters with mean post-sampling filter mass of 116 ± 3.6 mg, mean estimated PM MD using the standard method of 367 ± 589 μg, and mean estimated PM MD using the extraction method of 371 ± 589 μg. A Deming regression comparison of the two methods yields a slope of 0.9983 and a Pearson’s r of 0.999. A Bland-Altman assessment of the percent and absolute differences between the two methods shows the limits of agreement between 32.5% and 25.5% and -61.9 and 50.1 μg, respectively. The 99% confidence interval of the mean difference in mass deposition between the two methods is -5.8 ± 4.5 μg. These data demonstrate that estimating pre-sampling PTFE filter mass by extracting PM from sampled filters is a viable technique for gravimetric filter analysis. This method is of use in recovering pre-sampling filter weights that have been lost, incorrectly measured, or otherwise compromised.

Оценка нефтеемкостных свойств сорбентов в условиях различных температур

Objective: The oil capacity properties of the sorbents used for oil collection are qualitatively estimated at various temperatures. One of the factors securing sustained rail transport development is taking measures to prevent and eliminate the accidental spillages of dangerous goods including oil and oil products. Such accidents occur causing significant environmental contamination. Methods: Using sorbents for containment and elimination of such accidents has a good track record. Their properties have not been, however, sufficiently investigated at various temperatures. The sorbents’ oil capacity is determined by the standard gravimetric method using the difference between the weight of a sorbent impregnated with oil product and that of a pure sorbent based on 1 g (kg) of a pure sorbent. Results: Oil viscosity grows as the temperature goes down. The research findings show higher sorbents’ oil capacity figures caused by a changed oil recovery mechanism due to its higher viscosity: at a low or moderate viscosity, oil sorbs inside the sorbent volume, whereas at a high viscosity (above 200 mm2/s) sorbent surface adhesion occurs. Practical importance: A qualitative analysis of sorbents is important for ensuring environmental safety.

Time-Resolved Particulate Emissions Monitoring of Cookstove Biomass Combustion Using a Tapered Element Oscillating Microbalance

ABSTRACTIn this work, a tapered element oscillating microbalance (TEOM) system is developed to measure time-resolved cookstove particulate matter (PM) emissions less than 2.5 µm in diameter. The TEOM system requires modifications and calibration for cookstove applications to provide results consistent with the standard gravimetric filter method. We obtained a TEOM calibration constant of 0.67 for cookstove emissions. The TEOM system enables the correlation of operator actions and operating conditions with transient particulate emission events. We show that PM produced during refueling and lighting phases can significantly contribute to total particulate emissions over a cookstove comparison test, especially for cleaner stoves.

Moisture Adsorption Studies on Soy - Mumu Supplemented with Moringa Leaf Powder

Moisture adsorption Studies was carried out on Soy-mumu, a Nigerian cereal-based food product supplemented with 0, 10, 15 and 20% Moringa leaf powder at four different temperatures(20°C, 30°C, 40°C and 50°C) using the standard static gravimetric method. The different blends of Soy-mumu products were subjected to water activities of 0.1 – 0.957 for each of the four temperatures (20°C, 30°C, 40°C and 50°C) and data obtained were analysed using Oswin, Henderson and GAB models while thermodynamics of moisture transfer were estimated using Clausius-Clapeyron and kinetic compensation equations. The moisture adsorption isotherms were sigmoid in shape (type II). The equilibrium moisture content (EMC) of the Soy-mumu products increased with increase in water activity at constant temperature and were lower as the temperature increased at constant water activity. The sorptive capacity of Soy-mumu products increased with increasing levels of Moringa leaf powder supplementation and exhibited higher isotherms. Using the percent root mean square of error (% RMS), Oswin model gave the best fit for describing the adsorption isotherms of the Soy-mumu products while GAB and Henderson models fitted poorly (<10% RMS). Monolayer moisture content (Mo) and surface area (So) of adsorption decreased with increase in temperature. The GAB monolayer moisture contents were higher than BET monolayer moisture contents. The isosteric heat of sorption generally decreased as the moisture content increased. The maximum isosteric heat (ΔHst) was 14.1928; 14.19288; 37.0272 and 57.9120kj/mol for samples that were supplemented with 0, 10, 15 and 20% Moringa leaf powder respectively. The enthalpy-entropy compensation theory is suitable for describing the moisture adsorption phenomenon of the Soy-Mumu products.

Simultaneous detection of ethanol, ether and acetone by mid-infrared cavity ring-down spectroscopy at 3.8 μm

Mid-infrared cavity ring-down spectroscopy (CRDS) using an external cavity, widely tunable pulsed quantum cascade laser operating at 3.8 μm, was employed for simultaneous detections of ethanol, ether and acetone in this paper. The experiments were performed with a maximum cavity mirror reflectivity of 99.915 % between the wave number 2614 and 2634 cm−1, leading to an effective optical path length of 588 m. The absorption spectra of ethanol, ether and acetone were measured with high spectral resolution in the range of 2614–2634 cm−1, and the spectroscopic analysis of the mixture of ethanol, ether and acetone with overlapping absorption spectra was demonstrated. The experimentally achieved detection limits ( $$3\sigma$$ , or three times of standard deviation) for ethanol, ether and acetone were 157, 60 and 280 ppb, respectively. The simultaneously measured concentration results were in good agreement with the results with the standard gravimetric method, indicated that the mid-infrared CRDS has the potential for multi-component trace gas detection as well as for spectroscopic measurements of multi-broadband absorbers.

A high-sensitivity scanning magnetometer based on the giant magneto-impedance effect for measuring local magnetic fields of corrosion currents

The design, main characteristics, and specific features of a new high-sensitivity magnetometer based on the giant magneto-impedance (GMI) effect in amorphous ferromagnetic microwires are considered. It is shown that, in addition to measuring homogeneous fields, the device is capable of detecting weak local magnetic fields of conduction currents and ion currents involved in corrosion processes. Results of in situ magnetic measurements of corrosion processes in the model system of copper–zinc in a sulfuric acid solution qualitatively agree with the data of direct corrosion tests employing the standard gravimetric method.

Mathematical and neural network modelling of the adsorption characteristics of dried African catfish (clarias gariepenus)

Moisture adsorption isotherms of dried fillets of African catfish (Clarias gariepenus) were determined at 23, 30 and 45°C in the range 0.11 to 0.93 of water activity, using the standard gravimetric static method. The data obtained from the experiments were fitted to four popular mathematical models [the Brunauer, Emmett and Teller (BET), Oswin, Henderson and the modified Guggenheim-Anderson-De Boer (GAB)] and to a set of artificial neural network (ANN) models. The modified GAB outperformed the other mathematical models [with coefficient of determination R2 = 0.96, mean relative error (MRE) = 6.64%] but the ANNs were more accurate (with the best giving R2 = 0.988 and MRE = 3.56%) in predicting the moisture adsorption isotherms of the dried catfish. The knowledge of the adsorption isotherms would be very useful in the design of packages, prediction of storage stability and for calculating moisture changes that may occur during storage.

Mathematical and neural network modelling of the adsorption characteristics of dried African catfish (clarias gariepenus)

Moisture adsorption isotherms of dried fillets of African catfish (Clarias gariepenus) were determined at 23, 30 and 45°C in the range 0.11 to 0.93 of water activity, using the standard gravimetric static method. The data obtained from the experiments were fitted to four popular mathematical models [the Brunauer, Emmett and Teller (BET), Oswin, Henderson and the modified Guggenheim-Anderson-De Boer (GAB)] and to a set of artificial neural network (ANN) models. The modified GAB outperformed the other mathematical models [with coefficient of determination R2 = 0.96, mean relative error (MRE) = 6.64%] but the ANNs were more accurate (with the best giving R2 = 0.988 and MRE = 3.56%) in predicting the moisture adsorption isotherms of the dried catfish. The knowledge of the adsorption isotherms would be very useful in the design of packages, prediction of storage stability and for calculating moisture changes that may occur during storage.

Estimation of extravascular lung water using the transpulmonary ultrasound dilution (TPUD) method: a validation study in neonatal lambs.

Increased extravascular lung water (EVLW) may contribute to respiratory failure in neonates. Accurate measurement of EVLW in these patients is limited due to the lack of bedside methods. The aim of this pilot study was to investigate the reliability of the transpulmonary ultrasound dilution (TPUD) technique as a possible method for estimating EVLW in a neonatal animal model. Pulmonary edema was induced in 11 lambs by repeated surfactant lavages. In between the lavages, EVLW indexed by bodyweight was estimated by TPUD (EVLWItpud) and transpulmonary dye dilution (EVLWItpdd) (n = 22). Final EVLWItpud measurements were also compared with EVLWI estimations by gold standard post mortem gravimetry (EVLWIgrav) (n = 6). EVLWI was also measured in two additional lambs without pulmonary edema. Bland–Altman plots showed a mean bias between EVLWItpud and EVLWItpdd of −3.4 mL/kg (LOA ± 25.8 mL/kg) and between EVLWItpud and EVLWIgrav of 1.7 mL/kg (LOA ± 8.3 mL/kg). The percentage errors were 109 and 43 % respectively. The correlation between changes in EVLW measured by TPUD and TPDD was r2 = 0.22. Agreement between EVLWI measurements by TPUD and TPDD was low. Trending ability to detect changes between these two methods in EVLWI was questionable. The accuracy of EVLWItpud was good compared to the gold standard gravimetric method but the TPUD lacked precision in its current prototype. Based on these limited data, we believe that TPUD has potential for future use to estimate EVLW after adaptation of the algorithm. Larger studies are needed to support our findings.

Sorption isotherms modeling approach of rice-based instant soup mix stored under controlled temperature and humidity

Moisture sorption isotherms of rice-based instant soup mix at temperature range 15–45°C and relative humidity from 0.11 to 0.86 were determined using the standard gravimetric static method. The experimental sorption curves were fitted by five equations: Chung-Pfost, GAB, Henderson, Kuhn, and Oswin. The sorption isotherms of soup mix decreased with increasing temperature, exhibited type II behavior according to BET classification. The GAB, Henderson, Kuhn, and Oswin models were found to be the most suitable for describing the sorption curves. The isosteric heat of sorption of water was determined from the equilibrium data at different temperatures. It decreased as moisture content increased and was found to be a polynomial function of moisture content. The study has provided information and data useful in large-scale commercial production of soup and have great importance to combat the problem of protein-energy malnutrition in underdeveloped and developing countries.

A thermogravimetric analysis (TGA) method to determine the catalytic conversion of cellulose from carbon-supported hydrogenolysis process

The ability to determine the quantity of solid reactant that has been transformed after a catalytic reaction is fundamental in accurately defining the conversion of the catalyst. This quantity is also central when investigating the recyclability of a solid catalyst as well as process control in an industrial catalytic application. However, when using carbon-supported catalysts for the conversion of cellulose this value is difficult to obtain using only a gravimetric method. The difficulty lies in weighing errors caused by loss of the solid mixture (catalyst and non-converted cellulose) after the reaction and/or moisture adsorption by the substrate. These errors are then propagated into the conversion calculation giving erroneous results. Thus, a quantitative method using thermogravimetric analysis (TGA) has been developed to determine the quantity of cellulose after a catalytic reaction by using a tungsten carbide catalyst supported on activated carbon. Stepped separation of TGA curves was used for quantitative analysis where three thermal events were identified: moisture loss, cellulose decomposition and CO/CO2 formation. An analytical curve was derived and applied to quantify the residual cellulose after catalytic reactions which were performed at various temperatures and reaction times. The catalytic conversion was calculated and compared to the standard gravimetric method. Results showed that catalytic cellulose conversion can be determined using TGA and exhibits lower uncertainty (±2%) when compared to gravimetric determination (±5%). Therefore, it is a simple and relatively inexpensive method to determine catalytic conversion for scientific and industrial applications.

Preparation of Gas Standard Mixture of R134a by an Injection Method

An injection method was proposed for the preparation of R134a in N2 gas standards at 10 nmol/mol. The standard gravimetric method of ISO6142 was used as verification for the injection method. Results showed that good consistence between the injection method and the standard gravimetric method could be obtained. The contribution of the injection method to the standard uncertainty was about 0.92%, almost in the same order of magnitude with contribution of the standard gravimetic method.

Fringing Field Capacitive Sensor for Measuring Soil Water Content: Design, Manufacture, and Testing

Capacitors are used as sensors in several applications. Typically, the quantity to be measured changes either the geometric properties of the structure used as a capacitive sensor or the physical properties of the dielectric between the electrodes of that structure. On the other hand, if the sensor geometry maximizes the capacitance due to fringing, then the possibilities are totally different. In this case, the electric field can be projected onto the test sample. This paper covers the usage of fringing field sensors to measure the water present in the soil. We examine how the geometry of the PCB-made interdigited electrode structure influences the characteristics of the sensor. However, fringing field sensors are difficult to be analytically modeled due to its intrinsic nonlinear characteristic. Therefore, our conclusions were mainly based on results of simulations, but we also tried to reproduce the results of the simulations experimentally. Also, we discuss a circuit that converts the changes in the sensor's capacitance into variations in the width of a pulse signal. Finally, the proposed solution has been experimentally compared with the standard gravimetric method to quantify the water content in the soil. The results were encouraging since the proposed sensor's measurements fit to the experimental data with a coefficient of determination R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> = 0.94.