Determination Of Water Uptake Research Articles

An improved method for the simultaneous determination of water uptake and swelling of tablets

Water uptake and swelling of tablets are processes occurring during active pharmaceutical ingredient (API) release. Thereby, disintegration is promoted and the enhanced exposure of API surface area to the release medium facilitates API dissolution. An experimental set-up for the simultaneous and time-resolved determination of water uptake and swelling of tablets has been developed. Water uptake was determined with a balance and swelling was determined with a camera. To validate the gravimetrical analysis, real-time water uptake measurements with inert test specimens were performed. The standard deviation of these measurements was considered to depict precision. A complementary gravimetrical analysis was employed to determine accuracy. For both, precision and accuracy, a maximum deviation of 6% was found. An algorithm for the symmetry-based 3D volume reconstruction was applied to obtain volumes of the tablets from 2D images. X-ray micro computed tomography was used to validate the accuracy and the determined volumes were in good accordance within 6% deviation. A case study with binary formulations of a filler and disintegrants confirmed reproducibility and demonstrated the ability of the method to discriminate formulation characteristics, such as disintegrant type, composition and porosity for water uptake and swelling with the necessary temporal resolution.

Preparation and application of epoxidized natural rubber from Artocarpus heterophyllus gum

Epoxidized jackfruit gum (EJG) was prepared and characterized. An attempt to prepare a solid polymer electrolyte from EJG was made. The characterizations of epoxidized jackfruit gum were carried out through FT-IR spectroscopy, NMR spectroscopy, gel permeation chromatography, nitrogen content determination, water uptake determination and ion exchange capacity. The ion conductivity, differential scanning calorimetry, and SEM images of the blends of EJG and LiClO4 were characterized. The results indicated the epoxy group content of the sample achieved 95 mol% after 3 h of the epoxidation. During the epoxidation, the nitrogen content reduced, whereas the phospholipid content of the samples did not change. The molecular weight of samples reduced during the epoxidation. The ion conductivity of EJG/LiClO4/epoxidized natural rubber was improved, i.e. in order of 10−4 S/cm which was attributed to the presence of epoxy group in EJG. The liquid crystal may form in EJG/LiClO4 blends. These phenomena may suggest the strong interaction between epoxy group in EJG and LiClO4.

Spatially Resolved Root Water Uptake Determination Using a Precise Soil Water Sensor.

To answer long-standing questions about how plants use and regulate water, an affordable, noninvasive way to determine local root water uptake (RWU) is required. Here, we present a sensor, the soil water profiler (SWaP), which can determine local soil water content (θ) with a precision of 6.10-5 cm3 ⋅ cm-3, an accuracy of 0.002 cm3 ⋅ cm-3, a temporal resolution of 24 min, and a one-dimensional spatial resolution of 1 cm. The sensor comprises two copper sheets, integrated into a sleeve and connected to a coil, which form a resonant circuit. A vector network analyzer, inductively coupled to the resonant circuit, measures the resonance frequency, against which θ was calibrated. The sensors were integrated into a positioning system, which measures θ along the depth of cylindrical tubes. When combined with modulating light (4-h period) and resultant modulating plant transpiration, the SWaP enables quantification of the component of RWU distribution that varies proportionally with total plant water uptake, and distinguishes it from soil water redistribution via soil pores and roots. Additionally, as a young, growing maize (Zea mays) plant progressively tapped its soil environment dry, we observed clear changes in plant-driven RWU and soil water redistribution profiles. Our SWaP setup can measure the RWU and redistribution of sandy-soil water content with unprecedented precision. The SWaP is therefore a promising device offering new insights into soil-plant hydrology, with applications for functional root phenotyping in nonsaline, temperature-controlled conditions, at low cost.

Effectiveness of non-Fickian diffusion model on the water uptake determination of organic coatings

Effectiveness of non-Fickian diffusion model on the water uptake determination of organic coatings

Antibacterial properties of carboxymethyl chitosan Schiff-base nanocomposites loaded with silver nanoparticles

Nanocomposites of anisaldehyde and salicylaldehyde carboxymethyl chitosan (CMC)-Schiff bases/silver nanoparticles have been prepared and characterized. Their antibacterial activities were evaluated against (Bacillus Subtilis, Staphylococcus aureus and Streptococcus faecalis) as Gram + ve bacteria and the Gram − ve bacteria (Escherichia coli, Neisseria gonorrhoeae and Pseudomonas aeruginosa). The prepared compounds were characterized using FTIR spectroscopy, scanning electron microscopy, transmission electron microscopy and thermogravimetric analysis. Determination of water uptake of both CMC-Schiff bases/silver nanoparticles was carried out. Minimum inhibitory concentrations (MIC) of the prepared nanocomposites were determined as well. Cytotoxic activity of the investigated nanocomposites were evaluated against liver carcinoma cell; HEPG2 and breast cell line; MCF7.

Effectiveness of non-Fickian diffusion model on the water uptake determination of different organic coatings

Water uptake and permeation rates are critical parameters for the assessment of anti-corrosive organic coatings. Theses parameters can be estimated conveniently using electrochemical impedance spectroscopy measurements (EIS). Most of the defects and the origin of catastrophic failures of organic coatings are associated with water and concomitant pollutants transfer through the protective film to the substrate. Although, the diffusion of water in organic coating is well understood, there is a lack of experimental comparison between in situ electrochemical techniques and standardised methods for water uptake determination in free-standing films. In this study, the anti-corrosive performance and water uptake rates in 4 commercial anti-corrosive organic coatings applied on galvanized steel were determined under continuous immersion in 0.6 mol dm−3 NaCl and 0.6 mol dm−3 Na2SO4 by in situ EIS measurements. Parameters associated with water uptake were compared against water vapor permeation rates in free-standing films measured by wet-cup method (ASTM-D1653). It was found that EIS estimations of water permeation rates only agree with the wet-cup method when non-Fickian diffusion and coating swelling effects were considered. Remarkably, the presence and nature of two contaminants (Cl− and SO42−) did not affect considerably the permeation rates but had a significant impact on water saturation times and swelling. EIS and wet-cup methods demonstrated to be consistent and suitable methods to study the diffusion of water. However, EIS provided a more detailed survey of water uptake and associated degradation processes.

Determination of water uptake in organic coatings deposited on 2024 aluminium alloy: Comparison between impedance measurements and gravimetry

Abstract Electrochemical impedance spectroscopy (EIS) and gravimetric measurements on two water-based coatings, containing either SrCrO4 or a mixture of Cr(VI)-free pigments and deposited on 2024 aluminium alloy, were performed to follow the water uptake in a 0.5 M NaCl solution as a function of exposure time. To account for the observed non-ideal capacitive behaviour, the coating capacitance and dielectric constant values were extracted from the EIS data in two ways: (i) by using a complex-capacitance representation and (ii) by fitting to the EIS data a model that assumed an exponential distribution of coating resistivity. The agreement of values obtained by these independent methods served to validate the model used to account for the observed pseudo constant-phase-element (CPE) behaviour of the coatings. The water uptake calculated from dielectric constant values, employing a linear combination formula, was in good agreement with that directly measured by gravimetry, using supported-films.

Carboxymethyl Starch Excipients for Drug Chronodelivery.

Carboxymethyl starch (CMS) is a pH-responsive excipient exhibiting also interesting properties for applications in delayed drug delivery systems. This work was aimed to investigate the release properties of monolithic and dry-coated tablets based on ionic sodium CMS and on protonated CMS, formulated with three model tracers: acetaminophen, acetylsalicylic acid (ASA), and sodium diclofenac. The sodium or protonated CMS were obtained from the same CMS synthesis by controlling the final pH of reaction media. The two forms of CMS were confirmed by the Fourier transform infrared spectroscopy. The in vitro dissolution profiles for monolithic and double core tablets were different and allowed a better understanding of characteristics of the two excipient forms. It was found that the protonated CMS exhibited a better stability in simulated gastric fluid in comparison to its sodium salt in monolithic dosage forms, whereas both excipients afforded a complete gastric protection of drugs when formulated as dry-coated dosages. Determination of water uptake and erosion rate of monolithic matrices based on the two CMS forms showed different mechanisms involved in the delivery of the three model active molecules in simulated intestinal media. When pancreatic enzymes were added in dissolution media, the drug release was accelerated showing that CMS is still a substrate for alpha-amylase. Both sodium and protonated starch excipients, formulated as dry-coated dosages, afforded a good gastro-protection and allowed a drug chronodelivery at various intervals up to 4-5h. They could be considered as an alternative for delayed delivery and a solvent-free coating procedure.

Effects of Different Pretreatments and Seed Coat on Dormancy and Germination of Seeds of Senna obtusifolia (L.) H.S. Irwin & Barneby (Fabaceae)

<p class="1Body">The seed dormancy of <em>Senna obtusifolia</em> was investigated through various methods, namely pretreatments in concentrated sulfuric acid, 2% potassium nitrate (KNO<sub>3</sub>), 99% ethanol, 99% methanol, and in hydrogen perioxide; examination of the seed coverings; and the determination of water uptake by the seeds in order to ascertain the most effective technique for breaking dormancy and also determine the dormancy type. The results showed that sulfuric acid treatment recorded the highest germination (100%); followed by 2% hydrogen peroxide treatment (24%) in 15minutes immersion. The methanol and ethanol pretreatments gave 18.33% and 16.5% germinations respectively. Pretreatment in 2% potassium nitrate gave the lowest germination (8.50%), while the intact seeds of <em>S. obtusifiolia</em> (control) gave 0% germination. The anatomy of the seed coat indicated the presence of hard, thickened and specialized cells of cuticle, macrosclereids, osteoscereids, and disintegrated parenchyma layers. The water uptake of intact seeds was low (13.5%) after 24 hr imbibitions. These findings revealed that the seed coat acts as barrier to germination by preventing water absorption, possibly gaseous diffusion in and out of the seed and conferring mechanical resistance to the protrusion of embryo. Pretreatments, such as immersion in H<sub>2</sub>SO<sub>4 </sub>will soften the seed coat and permit germination. Seed dormancy in <em>S. obtusifolia </em>can be considered of physical nature and classified as physical dormancy. The results obtained in this study may serve as useful information in the production and improvement of <em>S. obtusifolia </em>seedlings, as knowledge on seed dormancy and germination is a critical factor and requirements to the understanding of the propagation of this plant either in situ or ex-situ, in view of the economic potentials/attributes of this species.</p>

The Myth of the "Biphasic" Hyaluronic Acid Filler.

The terms "biphasic" and "monophasic" have been used frequently as a means of differentiating hyaluronic acid (HA) fillers. This type of categorization is based on misinterpretations of the term "phase" and provides no help to the practitioner when selecting the most appropriate product for each indication, patient, and injection technique. The purpose of this study was to analyze the properties of 2 HA filler families; Juvederm (JUV) (Allergan), often stated to be monophasic and Restylane (RES) (Galderma), often stated to be biphasic, and discuss what properties may have led to the use of the terms monophasic and biphasic. Three different methods were used for JUV and RES: determination of extractable HA; determination of water uptake; and microscopy. The analyzed products were shown to contain both observable gel particles and extractable HA and have the ability to absorb added water. The categorization of HA fillers as biphasic or monophasic was shown to be scientifically incorrect and should therefore be avoided. Further analytical measurement of the properties leading to this misinterpretation can provide information to discriminate and categorize HA fillers on a sounder scientific basis.

Membranes from Blended Ionomer/PVDF Nanofibers: II. Interplay Between Properties and Electric Response

Fact of Fiction: Do ion-exchange membranes really require complete water saturation in order to possess desirable conductivity? The fabrication of new proton-conducting membranes with a high conductivity at high temperature and low relative humidity conditions is a critically important research challenge for fuel cell developers [1]. Similarly, high conductivity and low crossover membranes are needed in redox flow batteries. Recently, membranes were made by nanofiber electrospinning solutions of perfluoroionomer + PVDF, followed by hot-pressing the resulting blended fiber mat into a dense membrane. These films have unusual and highly desirable properties for use in hydrogen/air fuel cells and/or aqueous flow batteries. In particular, some blended fiber membranes exhibit unusually high proton conductivity at very low water contents. The effect of processing on the complex interplay between the chemical composition, structure and conductivity mechanism of these innovative membranes is still poorly understood. Here we present a complete analysis of the physical-chemical properties as well as the conductivity mechanism of Nafion-PVDF (90wt%/10wt%) membranes obtained from a single fiber mat. These results are contrasted with data collected using a Nafion/PVDF blended membrane prepared by conventional solvent casting. The membranes are extensively characterized by thermoanalytical techniques (water uptake determination, HR-TGA, MDSC, DMA), vibrational spectroscopy (FT-IR ATR) [3], and broadband electric spectroscopy (BES). A Nafion-PVDF (90wt%/10wt%) membrane obtained from an electrospun single fiber mat shows a very low level of water (3 w%) and exhibits high conductivity. The two polymers are found to be well mixed with chains of Nafion surrounding those of PVDF. In addition, there is no evidence of bulk water domains but rather the water molecules are aligned along the polymer chains facilitating a fast proton transfer mechanism. The added benefit of the low water uptake is that there is negligible swelling of the membrane, rendering membranes of this type suitable for a variety of applications. BES measurements are carried out from -100 to 120°C and from 0.03 to 107Hz and are able to elucidate different kind of conductivity mechanisms. The electric response of the Nafion-PVDF (90/10) mat (Figure 1a) and the blend fiber membrane (Figure 1b) are very different from those of Nafion [4], while that obtained from solvent casting (Figure 1c) is similar to Nafion for T>0°C and to mat membrane at T<0°C. Acknowledgements This research was funded by the Strategic Project of the University of Padua “Materials for Membrane-Electrode Assemblies to Electric Energy Conversion and Storage Device (MAESTRA)” and by Veneto Nanotech S.C.p.a. (Venice). REFERENCES [1] V. Di Noto, T.A. Zawodzinski, A.M. Herring, G.A. Giffin, E. Negro, S. Lavina, Int. J. Hydrogen Energy 37, 6120 (2012). [2] J.B. Ballengee, P.N. Pintauro, J. Membr. Sci. 442, 187 (2013). [3]. E. Negro, M. Vittadello, K. Vezzù, S. J. Paddison, V. Di Noto, Solid State Ionics 252, 84 (2013). [4] V. Di Noto, M. Piga, G. Pace, E. Negro, S. Lavina, ECS Trans. 16, 1183 (2008). Figure 1

Determination of Water Uptake of Polymeric Ion-Selective Membranes with the Coulometric Karl Fischer and FT-IR-Attenuated Total Reflection Techniques

The water uptake of plasticized poly(vinyl chloride) (PVC) and silicone rubber (SR) based calcium-selective membranes which are commonly used in solid-contact and coated-wire ion-selective electrodes (SC-ISEs and CWEs) was quantified with the oven based coulometric Karl Fischer (KF) technique. Two different membrane types were studied: (1) the plasticized PVC or SR (RTV 3140) membrane matrix without other added membrane components and (2) the full Ca(2+)-selective membrane formulation consisting of the membrane matrixes, potassium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate and calcium ionophore IV (ETH 5234) or calcium ionophore I (ETH 1001). The membranes were contacted for 24 h either asymmetrically from one side or symmetrically from both sides with deionized water (DIW) or 0.1 M solutions of CaCl(2), KCl, or NaCl. It was found that the water uptake was higher for symmetrically contacted membranes. The highest water uptake (0.15-0.17 wt %) was obtained for the plasticized PVC based Ca(2+)-selective membranes in DIW, whereas the water uptake was lower in 0.1 M electrolyte solutions. Symmetrically contacted Ca(2+)-selective SR membranes had much lower water uptake in 0.1 M CaCl(2) (0.03 wt %) than their plasticized PVC counterparts (0.1 wt %). However, the (noncontacted) SR membranes contained initially much more water (0.09-0.15 wt %) than the PVC membranes (0.04-0.07 wt %). Furthermore, in good accordance with the KF measurements, it was verified with FT-IR-attenuated total reflection (ATR) spectroscopy that the water content at the substrate/membrane interface and consequently in the whole membrane was influenced by the electrolyte solution.

Effect of Annealing on the Crystallization of Poly Vinyl Chloride for Drug Delivery System

Poly vinyl alcohol has been studied for its ability to form crystallites by using annealing method. Semicrystalline films of poly vinyl alcohol (PVA) were prepared by casting 11.5 wt. % and 13 wt. % PVA aqueous solution onto glass slides at annealing temperature range 90 -120°C and duration time 15- 60 minute. This allowed the macromolecules to form crystallites, small regions of folded and compacted chains separated by amorphous regions where single PVA chain may pass through several of these crystallites. Degree of crystallinity of PVA films (hydrogels) was determined by method of density; on the other hand the swelling behavior was conducted by the determination of water uptake, wet degree of crystallinity, gel fraction and solubility. The results of PVA films showed that water uptake decreased with increasing temperature, time of annealing and PVA concentration, while degree of crystallinity increased, and gel fraction and solubility decreased with increasing temperature and time of annealing. The maximum dry and wet degree of crystallinity was 64% and 36% respectively at 120°C and 60 min.

Variability of water uptake studies of biomedical polymers

AbstractWater uptake influences many properties of polymers and has been widely studied. In the context of polymeric biomaterials, several publications reported an unusual high variability of analytical results, without further investigating the cause for this phenomenon. Using selected polymers from the library of L‐tyrosine‐derived polyarylates and poly(D,L lactic acid), we showed that nonaged and nonannealed compression molded film samples exhibit the typical large variation in water uptake observed in previous reports. The introduction of an annealing step allows accurate and reproducible water uptake measurements for these polymers. We evaluated the use of 3H‐radiolabeled water for the determination of water uptake, finding that the use of radiolabeled water yields statistically indistinguishable measurements, compared to gravimetric methods, while providing significant advantages in throughput and sensitivity. Using the recommended methods of annealing and 3H‐radiolabled water, the water uptake profiles of 24 polymers of the library of L‐tyrosine‐derived polyarylates are reported. This article addresses experimental concerns related to water uptake studies and may assist other researchers in improving the accuracy of their water uptake results. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Branched polyesters based on poly[vinyl-3-(dialkylamino)alkylcarbamate- co-vinyl acetate- co-vinyl alcohol]-graft-poly( d, l-lactide- co-glycolide): Effects of polymer structure on in vitro degradation behaviour

Branched polyesters of the general structure poly[vinyl-3-(dialkylamino)alkylcarbamate- co-vinyl acetate- co-vinyl alcohol]-graft-poly( d, l-lactide- co-glycolide) have shown potential for nano- and micro-scale drug delivery systems. Here the in vitro degradation behaviour with a special emphasis on elucidating structure–property relationships is reported. Effects of type and degree of amine substitution as well as PLGA side chain length were considered. In a first set of experiment, the weight loss of solvent cast films of defined size from 19 polymers was measured as a function of incubation in phosphate buffer (pH 7.4) at 37 °C over a time of 21 days. A second study was initiated focusing on three selected polymers in a similar set up, but with additional observation of pH influences (pH 2 and pH 9) and determination of water uptake (swelling) and molecular weights during degradation. Scanning electron micrographs have been recorded at selected time points to characterize film specimens morphologically after degradation. Our investigations revealed the potential to influence the degradation of this polymer class by the degree of amine substitution, higher degrees leading to faster erosion. The erosion rate could further be influenced by the type of amine functionality, DEAPA-modified polyesters degrading as fast as or slightly faster than DMAPA-modified polyesters and these degrading faster than DEAEA–PVA- g-PLGA. As a third option the degradation rate could be modified by the PLGA side chain length, shorter side chains leading to faster erosion. As compared to linear PLGA, remarkably shorter degradation times could be achieved by grafting short PLGA side chains onto amine-modified PVA backbones. Erosion times from less than 5 days to more than 4 weeks could be realized by selecting the type of amine functionality, the degree of amine substitution and the PLGA side chain length at the time of synthesis. In addition, the pathway of hydrolytic degradation can be tuned to be either mainly bulk or surface erosion.

Influence of the solution cation mobility on the water uptake estimation of PVC Plastisol freestanding films by EIS

In this work, the influence of the outer solution cation mobility on the electrochemical behaviour of PVC Plastisol freestanding films was studied. For that purpose, the paint films were immersed in 0.5 M and 0.05 M chloride solutions with different cations (Na +, K +, Cs +). The electrochemical impedance spectroscopy (EIS) was the technique chosen for this study and estimated values of film capacitance and resistance were calculated. For PVC Plastisol films, it was observed that the ion diffusion depends on the outer solution concentration. To explain such results different mechanisms for the ionic diffusion were considered. For higher concentration solutions the ions of the outer solution must diffuse into the film, while for lower concentration solutions the dissolution inside the film occurs followed by ionic diffusion from the film to the outer solution. The water uptake was determined by EIS and gravimetry techniques. The Brasher and Kingsbury (BK) and the low frequency solution (LF) models were used to estimate this parameter by the EIS technique. A direct dependency between water uptake and solution concentration was obtained by this technique, while by gravimetry an inverse relation was obtained. However, the LF model presented water uptake values better correlated with the gravimetric ones comparatively to the BK equation. For the more concentrated solutions, the cation mobility influenced the water uptake estimated by EIS, whereas, such dependency was not observed with the gravimetric technique. The results obtained in this work suggest that the outer solution resistivity and consequently the film resistance influence the water uptake measurements and should take part in any improved model used for water uptake determination.

Physicochemical monitoring of wood coating degradation related to fungal disfigurement

Analytical methods for the assessment of coating degradation are numerous. While providing data concerning the physicochemical condition of the sample during weathering, it is worth investigating the relation with fungal disfigurement in laboratory experiments. Coated wooden samples were subjected to artificial ageing for 2000 h while their behaviour was monitored with infrared spectroscopy, UV spectroscopy, differential scanning calorimetry, water uptake determination and contact angle measurements. Data analysis comprised extraction of quantitative values from IR series, UV absorption calculation, straightforward mathematical operations for glass transition determination, water uptake coefficient calculations and drop shape analysis of water droplets. Unweathered and weathered samples were also subjected to fungal attack in a laboratory set-up based on the principles of the EN 152 test procedure. Linking degradation data with biological susceptibility provides a better insight in property related biological damage.

Desenvolvimento instrumental para determinação direta da perda de água em plantas por meio do monitoramento do fluxo de seiva

Crop water monitoring is important for a detailed irrigation control. It is desirable to develop reliable and portable techniques to properly assess the water uptake of agricultural crops. An experiment was conducted in the IAC/Jundiai, state of Sao Paulo aiming to achieve such developments. An integrated system based on heat pulse technique was designed and built in order to assess water uptake. Different probe configurations were tested, aiming to find the best sensor profile for field usage. Field and laboratory grown maize were used to calibrate the system. Testing the system on maize stems resulted in a coherent relationship between heat transport and sap flux, for two of the sensor configurations tested. Field results of water uptake determination, obtained comparatively with standard methodology, agreed with the daily-paired data and yielded reasonable values based on statistical Willmot index.

Prediction and Determination of Water Uptake in Packaged Yerba Mate

Permeability of different packaging materials and the water uptake were studied in stored yerba mate at different conditions of humidity and temperature. Water vapour transmission rate (WVTR) was evaluated using the quasi-isostatic method. During storage at high relative humidity conditions, WVTR values were of 500 gm2/day for paper and ranged from 16 to 22 gm2/day for laminated films. Values of package permeability and data of food isotherms were used to calculate the variation of internal water vapour activity and to predict the yerba mate water uptake. The predicted and experimental values were in good agreement. For similar high humidity storage conditions, yerba mate packaged with paper reached critical humidity content (9.5% d.b.) at the second day of storage whereas for the laminate films the humidity content stood below the critical value until a month of exposure.

Experimental weathering of marlstone from Přednı́ Kopanina (Czech Republic)—historical building stone of Prague

Romanesque builders favoured marlstones because of their easy workability. Unfortunately, this rock rapidly deteriorates when exposed to the external atmospheric conditions. Artificial weathering experiments were conducted on marlstone from Přednı́ Kopanina quarry near Prague (Czech Republic) in order to determine: (A) which weathering factor presents major danger to this rock type, and (B) which of the test methods provide the most reliable measure of the intensity of rock disintegration. Rock specimens prepared from fresh rock were subjected to standardized freeze–thaw cycles and salt crystallization tests, and to the accelerated weathering in climatic chamber using SO 2 and a combination of freeze–thaw and SO 2 cycles. Stone properties were evaluated by non-destructive and destructive techniques including ultrasonic velocity measurements, determination of water uptake by capillary action, mechanical testing, detailed porosimetric analysis and microscopic study.