Measured Dissolution Rates Research Articles

Structure–property relations of sodium iron phosphate nuclear waste glasses: Effects of iron redox ratio and glass composition

AbstractIron phosphate glasses, known for their exceptional chemical durability and potential applicability in nuclear waste management, have gained significant attention over the years. The structures of these glasses are complicated by the coexistence of Fe3+ and Fe2+, which plays a crucial role in determining their structures and properties. This work uses molecular dynamics simulations to study the structural changes in Na2O–Fe2O3–P2O5 glasses with varying glass composition and Fe2+/Fe3+ redox ratio. It was found that the redox ratio and modifier contents significantly affected the short‐range and medium‐range orders in the glasses. Significant changes in the local environments around P5+ and Fe3+ were observed, as reflected by the bond distances and coordination numbers. Na+ cations are found to preferentially associate with Fe3+ (rather than Fe2+), whereas Fe2+ has stronger association with P5+ than Na+, confirming the structural role of Fe2+ as a glass modifier. The disruptions in P–O–P linkages upon increasing FeO suggest that FeO causes glass depolymerization. These glasses achieved higher connectivity with increasing ratios, conerting phosphorous Q2 to Q3 units and iron Q5 units to Q4 units. The decrease of nonbridging oxygen fractions with increasing ratios, through creating P–O–Fe linkages, is the main reason of enhanced network connectivity. Quantitative structure–property relationship analyses with different structural descriptors were used to correlate with measured properties. The analyses provided valuable insights into structure–property relationships, emphasizing the importance of choosing relevant energy parameters and defining glass network connectivity, particularly in Fnet descriptors. It was found the Fe–O–P linkage density exhibits strong correlations to measured dissolution rates, supporting the importance of these linkages in improving the chemical durability in iron phosphate glasses.

Dissolution Behaviors of Recycled Cement Paste and Lime in EAF Slag Under Static Conditions

Recycled cement paste (RCP) is a CaO-rich resource that is recycled from waste concrete and waste cement. For reducing environmental impact and promoting comprehensive resource utilization, RCP could partially replace lime as flux in electric arc furnace (EAF) steelmaking process. In this study, the dissolution behaviors of RCP and lime in EAF slag at 1400 °C and 1500 °C were investigated using static dissolution experiments. The measured dissolution rate constant of lime at 1400 °C and 1500 °C is 3.12×10−5 and 8.42×10−5 m/s, respectively, while that for RCP is 1.37×10−4 and 2.91×10−4 m/s, respectively. For the lime dissolution, a dense dicalcium silicate (C2S) product layer was generated at the dissolution interface, with the diffusion of Ca2+ in the C2S layer being the limiting step for the lime dissolution. However, for the RCP dissolution, no product layer was observed at the dissolution interface. Instead, a dissolution intermediate layer forms due to slag penetration. During the dissolution of RCP, Ca2+ and SiO44− diffuse from RCP layer to slag, while Fe2+ and AlO45− diffuse from slag to RCP layer accumulating in the dissolution intermediate layer. Furthermore, a dissolution model was developed based on current experimental results, which helps to predict dynamic dissolution process of lime and RCP in EAF slag. In general, the dissolution rate of RCP in EAF slag was much higher than that of lime, partially adding RCP as flux in EAF could accelerate the liquid slag formation in EAF steelmaking process.

Dissolution and early hydration of tetracalcium aluminoferrite (C4AF) in water and in aqueous sulfate solutions

Fe-rich cementitious phases, such as tetracalcium aluminate (C4AF), are likely the least characterized and understood components of ordinary cements, in terms of their reactivity and early-age reactions. In this study, we provided the first in-situ measurements of C4AF's absolute dissolution rates in water and aqueous sulfate solutions (Na2SO4, MgSO4 and CaSO4) along with its early-age hydration characterization. Upon contact with water, C4AF dissolved at a rate of 1.74 ± 0.23 μmol·m−2·s−1, and sulfates were found to inhibit its reaction. Among the three types of sulfates tested, CaSO4 exhibited the strongest inhibition effect, while Na2SO4 showed the weakest inhibition. Soon after the initial dissolution, the precipitation of hydrates occurred, and the presence of sulfates affected the overall hydration process of C4AF. These results enhance our understanding of C4AF's dissolution and early-age hydration behaviours, thereby advancing our knowledge of its hydration mechanisms.

Synthesis of In Situ Marine Calcium Carbonate Dissolution Kinetic Measurements in the Water Column

AbstractCalcium carbonate (CaCO3) dissolution is an integral part of the ocean's carbon cycle. However, laboratory measurements and ocean alkalinity budgets disagree on the rate and loci of dissolution. In situ dissolution studies can help to bridge this gap, but so far published studies have not been utilized as a whole because they have not previously been compiled into one data set and lack carbonate system data to compare between studies. Here, we compile all published measurements of CaCO3 dissolution rates in the water column (11 studies, 752 data points). Combining World Ocean Atlas data (temperature, salinity) with the neural network CANYON‐B (carbonate system variables), we estimate seawater saturation state (Ω) for each rate measurement. We find that dissolution rates at the same Ω vary by 2 orders of magnitude. Using a machine learning approach, we show that while Ω is the main driver of dissolution rate, most variability can be attributed to differences in experimental design, above all bias due to (diffusive) transport and the synthetic or biogenic nature of CaCO3. The compiled data set supports previous findings of a change in the mechanism driving dissolution at Ωcrit = 0.8 that separates two distinct dissolution regimes: rslow = 0.29 · (1 − Ω)0.68(±0.16) mass% day−1 and rfast = 2.95 · (1 − Ω)2.2(±0.2) mass% day−1. Above the saturation horizon, one study shows significant dissolution that cannot solely be explained by established theories such as zooplankton grazing and organic matter degradation. This suggests that other, non‐biological factors may play a role in shallow dissolution.

Stability of Bipolar Plates in Proton Exchange Membrane Water Electrolysis: Dissolution Studies of Titanium and Stainless Steel

Due to its high current densities and fast system response proton exchange membrane water electrolysis (PEMWE) is an ideal system for green hydrogen production from renewable energies. However, its widespread use is still hindered by the high costs rendering the produced green hydrogen not competitive. Therefore, a cost reduction is highly needed. The bipolar plates (BPPs) are causing a colossal factor in material costs. They are usually produced from titanium and coated with even more expensive materials such as gold or platinum. A possible, cheaper alternative is stainless steel. However, it is suspected to suffer from corrosion leading to the leaching of cations that can poison the catalyst or membrane.[1] Thus, we investigated the stability of BPP materials, the currently used titanium, and its cheaper alternative stainless steel (316L).[2] Therefore, we use a modified scanning flow cell setup coupled to an inductively coupled plasma mass spectrometer for investigating the stability of both materials on-line, as well as with scanning electron microscopy. To mimic the conditions at the BPP under operation, deionized (DI) water and highly diluted (0.5 mM) H2SO4 are chosen as electrolytes combined with a sample temperature of 60 °C.For Ti, we show that the dissolution is negligible, whereas 316L corrodes. For 316L, in DI water mainly Cr dissolves, while in the H2SO4 solution, the dissolution is more pronounced, and all alloy components are detected. Besides the pH value, the applied potentials play a crucial for its stability. However, our findings suggest that the contamination for a typical full cell architecture remains below 1 ppm, even for the highest measured dissolution rate of SS 316L.These capabilities of on-line high-throughput stability tests for BPP materials are, furthermore, used to investigate the influence of contaminations, such as F- or Cl-, and of the temperature-dependence on the stability of 316L. These results give further insights into 316L stability as BPP material and therefore contribute to the development towards cost-effective PEMWE.[1] a) N. Rojas, M. Sánchez-Molina, G. Sevilla, E. Amores, E. Almandoz, J. Esparza, M. R. Cruz Vivas, C. Colominas, Int. J. Hydrogen Energy 2021, 46, 25929-25943; b) H. Becker, J. Murawski, D. V. Shinde, I. E. L. Stephens, G. Hinds, G. Smith, Sustain. Energy Fuels 2023, 7, 1565-1603.[2] L. Fiedler, T. C. Ma, B. Fritsch, J. H. Risse, M. Lechner, D. Dworschak, M. Merklein, K. J. J. Mayrhofer, A. Hutzler, ChemElectroChem 2023, e202300373. Figure 1

Reaction order of near equilibrium calcite dissolution: Uncertainties and ambiguities of isotopic tracer methods

Dissolution of calcite in water is fundamental to geochemistry. Laboratory methods generally give consistent dissolution rates under conditions far from equilibrium, but close to equilibrium the measurement of dissolution using isotopes is complicated by poorly understood calcite-fluid isotopic exchange processes. This near-equilibrium isotopic exchange occurs in laboratory experiments at rates of order 10-9 to 10-13 mol/m2/s and decreases with experiment duration approximately as 1/time where time is measured from the start of the experiment. Such rates are fast enough to compete with dissolution in days-long experiments and consequently, net dissolution rates may not be measurable with isotopic tracer methods except in experiments carried out for long enough to allow the background exchange to dissipate sufficiently. To better define what should be expected for isotopic signals during dissolution, we develop a quasi-1D model for calcite dissolution that includes the mechanistically unconstrained isotopic exchange as well as solid state diffusion. We use the model, the observations reported in the literature, and the calcite dissolution rates in seawater reported by Naviaux et al., (2019a) to illustrate ambiguities in measurement of near-equilibrium calcite dissolution rates. The results suggest that the reaction order of calcite dissolution close to equilibrium could be 2 at both room temperature and the lower temperatures of the seafloor. The reaction order of near-equilibrium calcite dissolution is important for understanding calcite mineral surface processes, long-term behavior of dissolution on the seafloor, and alkalinity fluxes from modern seafloor sediments. Distinguishing between net dissolution, which affects fluid saturation state, and “exchange,” which doesn’t, is important but typically cannot be done with isotopic tracers alone.

Intrinsic dissolution rate modeling for the pharmacopoeia apparatus rotating disk compared to flow channel method

For a solid understanding of drug characteristics, in vitro measurement of the intrinsic dissolution rate is important. Hydrodynamics are often emphasized as the decisive parameter influencing the dissolution. In this study, experiments and computational fluid dynamic (CFD) simulations showed that the mixing behavior in the rotating disc apparatus causes an inhomogeneous flow field and a systematic error in the calculation of the intrinsic dissolution rate. This error is affected by both the experimental time and the velocity. Due to the rotational movement around the tablet center, commonly utilized in pharmacopeia methods, a broad variance is present with regard to the impact of fluid velocity on individual particles of the specimen surface. As this is significantly reduced in the case of uniform overflow, the flow channel is recommended for investigating the dissolution behavior. It is shown that rotating disc measurements can be compared with flow channel measurements after adjusting the measured data for the rotating disc based on a proposed, representative Reynolds number and a suggested apparatus-dependent correction factor. Additionally, modeling the apparatus-independent intrinsic dissolution rate for different temperatures in the rotating disc apparatus is possible using the adapted Levich’s equation.

Time-resolved measurements of the ultra-low dissolution rates of two-dimensional arrays of platinum nanoparticles

Methods for the quantitative evaluation of platinum (Pt) dissolution are required to allow catalyst lifetimes in polymer electrolyte fuel cells (PEFCs) to be predicted. However, it is challenging to detect very slow Pt dissolution rates occurring at low potential fluctuations, such as during load cycles, as may occur in automotive fuel cells. The dissolution behavior of Pt nanoparticles (NPs) is also greatly affected by the catalyst layer thickness, particle size and inter-particle distance, and it is difficult to assess these effects separately. To address these problems, the present work prepared two-dimensionally distributed Pt NPs using coaxial arc plasma deposition. An online ICP-MS system was subsequently used to evaluate the dissolution rate of these NPs. The results showed that Pt dissolved primarily during cathodic scans in association with potential cycling with a high upper potential limit, such as would occur in a PEFC start-stop cycle. This dissolution was accompanied by the formation of Pt oxide. There was little difference in dissolution behavior between Pt NPs and bulk Pt. An extremely slow time-resolved dissolution rate was successfully measured in the low potential region below 1.0 V vs. a standard hydrogen electrode, indicating that anodic dissolution was the predominant Pt dissolution mechanism. In this case, a clear difference in dissolution behavior between the NPs and bulk metal was observed. The onset potential for NPs dissolution was lower than that for bulk Pt and smaller NPs dissolved faster than larger ones.

Kinetics, stoichiometry, and mechanism of arsenopyrite-water interaction under anoxic conditions

Arsenopyrite dissolution is an important source of arsenic’s environmental occurrence and is well-studied under oxidative conditions. However, little is known of anoxic leaching of arsenopyrite by water, though it is probably one of the dominant abiotic processes controlling arsenic mobility in oxygen-limited environments such as groundwaters and paddy fields. The present study attempts to probe the mechanism of arsenopyrite-water interaction in anoxic environment through examining the pH dependence of dissolution kinetics and stoichiometry, as well as speciation changes both on the surface and in solution. Batch and flow-through experiments were first carried out to measure dissolution rates and the results showed alkaline pH mildly encourages As release. Furthermore, the dissolution was found to be near stoichiometric with respect to As and S but not with Fe/As or Fe/S, and the non-stoichiometry exhibited a negative dependence on pH. Combining speciation analyses that revealed the presence of H2O2, SO42− and S2O32− in solutions and a positive correlation of surface species Fe(III)-O, S(-II), and As(I), As(III), As(V), and As(-III) to solution pH, we interpreted the anoxic dissolution behavior of arsenopyrite through a mechanism that combines surface complexation and interfacial redox reactions. The kinetic measurements came to be concerning as data indicates arsenopyrite dissolution in anoxic environment can lead to water having arsenic concentrations above the 10 ppb WHO guideline value in one day at the experimental conditions. The observed H2O2 production indicated the dissolution is associated with or initiated by electron transfer despite the anoxic condition, further suggesting that a more comprehensive theory other than surface complexation model may be needed to better understand the geochemical behavior of As and possibly S in the context of sulfide mineral–water interactions.

Stability of Bipolar Plate Materials for Proton‐Exchange Membrane Water Electrolyzers: Dissolution of Titanium and Stainless Steel in DI Water and Highly Diluted Acid

AbstractThe widespread use of proton exchange membrane water electrolyzers (PEMWE) is hindered by their high cost, of which a colossal factor is caused by the bipolar plates (BPP). In this paper, we investigate the stability of two BPP materials on‐line with an optimized scanning flow cell setup coupled to an inductively coupled plasma mass spectrometer (SFC‐ICP‐MS), as well as scanning electron microscopy (SEM). The stability of currently used titanium and a cheaper alternative, stainless steel (SS) 316L, were characterized in deionized (DI) water and 0.5 mM H2SO4 to mimic the conditions at the BPP under operation. We show that the dissolution of Ti is negligible, whereas SS 316L degrades notably. Here, besides pH, the applied potentials play a crucial role. Nonetheless, even for the highest measured dissolution rate of SS 316L, the contamination in a full cell is estimated to remain below 1 ppm. This work illustrates the capabilities of on‐line high‐throughput stability tests for BPP materials and could therefore contribute towards optimization of cost‐effective PEMWE.

Structurally Unique Salts of Cyamemazine and Their Pharmaceutical Implications

The aim of this study was to prepare new crystalline salts of cyamemazine, an antipsychotic drug, with dicarboxylic acids, and compare their thermal stabilities, dissolution properties, and structural features. Among the eight acids investigated, we report novel salts with four acids, namely, L-malic, malonic, succinic, and fumaric acids. The study was extended to include the already known maleate and marketed L-tartrate salts as well. To the best of our knowledge, this is the first-ever study of the solid-state landscape of cyamemazine and report of its crystal structure. A rare phenomenon of kryptoracemic behavior exhibited by the L-tartrate, L-malate, and maleate salts adds an interesting perspective to this study since one of these salts is currently marketed. A powder second harmonic generation setup was developed as a tool to identify the kryptoracemates of this drug, and how this would help potentially in the production of specific solid forms of drugs is discussed. The dissolution rate measurement of the prepared salts confirmed that the succinate, L-malate, and malonate salts dissolve better and all of the new salts display improved thermal stability than the free base of the API, suggesting great potential for some of the candidates to be used for marketing purposes.

Aluminum Alloy Etching: New Insights By Element Resolved Electrochemical Analysis

Aluminum alloys are pickled and/or etched as a preliminary step prior to anodization or conversion coating. The chemistry of the etching/pickling process must be carefully engineered to avoid the enrichment of the alloying elements such metallic Cu which can interfere with subsequent treatments. Understanding and optimizing the etching process is therefore a major concern for the use of aluminum alloys, and especially, the Cu-rich high strength aluminum alloys.The etching reaction is a mixed potential process similar to other forms of aqueous corrosion. However, the dynamic nature of the interface makes it difficult to apply conventional electrochemistry to determine the rates and mechanisms of the different reactions and therefore, to predict how the etching process will vary with electrolyte composition. Among the many complicating factors, we can cite the very high dissolution rate of the alloy coupled with the formation of gas and the release of intermetallic particles. The dissolution of alloying elements such as Cu and Mg – the reactions of interest – occur at rates several orders of magnitude below that of Al dissolution. For example, Cu dissolution makes a negligible contribution to either electron exchange or mass loss. Finally, the rapid reaction rates and the short time scale of the process preclude the appearance of a true steady state, necessary for the interpretation of many electrochemical techniques.Therefore, to gain insight into the mechanism of the acid etching process, we have used an element-resolved electrochemical technique, atomic emission spectroelectrochemistry (AESEC) (Gharbi et al., 2016; Gharbi et al., 2017; Sultan et al., 2022). This permits the direct measurement of the elemental dissolution rates as a function of time, on an element-by-element basis.In this work, we illustrate the element-resolved electrochemical approach to surface treatment focusing on the acid etching of three alloys: a commercial high-strength AA7449 alloy (containing Zn, Cu, and Mg), and binary Al-Cu and Al-Mg alloys to represent the extremes of alloying element nobility. In sulfuric acid, the binary alloys also represent the extremes of selective versus congruent dissolution. The Al-Mg binary alloy undergoes a simultaneous, congruent dissolution mechanism with Mg dissolving simultaneously with Al. By contrast, the Al-Cu binary alloy exhibits a selective dissolution mechanism with Al dissolving to leave behind dealloyed metallic Cu on the surface of the material. This is ultimately followed by the release of Cu-rich particles due to anodic undermining.The electrolytes investigate in this work represent a range of oxidizing strengths from pure sulfuric acid to pure nitric acid and various mixtures of the two. The effect of Fe(III), an important component of many state-of-the-art etching solutions, was also investigated. Experimental elemental Evans diagrams were determined to clarify the electrochemical nature of the dissolution reactions, specifically how the elemental dissolution rates were related to one another and how they were coupled to the cathodic reactions.An example is shown in the Figure (right), based on the 2022 publication of Sultan et al. On the left, we show a cartoon representation of the dissolution process as determined for a high strength AA7449 alloy. On the right, we show the experimental element-resolved Evans diagram for the same alloy in sulfuric acid. It was found that Cu would not dissolve at the open circuit potential in sulfuric acid, but displayed active dissolution with a well-defined Tafel slope of 44 mV/decade at higher potential. The dissolution rate of Cu in the etching solutions was controlled by the redox potential of the electrolyte as determined by the addition of nitric acid and/or Fe(III). Based on our results, the Fe(III) additive in the presence of nitrate appears to serve a catalytic role, enhancing the rate of electron transfer between Cu and nitrate. The dissolution of Al and Mg were independent of potential suggesting simultaneous dissolution across an oxide film. The rates and mechanisms of Cu particle release will also be discussed.BBM Sultan, D Thierry, JM Torrescano-Alvarez, K Ogle, “Selective dissolution during acid pickling of aluminum alloys by element-resolved electrochemistry”, Electrochim. Acta, 404(2022)139737.O Gharbi, N Birbilis, K Ogle, “In-situ monitoring of alloy dissolution and residual film formation during the pretreatment of Al-alloy AA2024-T3”, J. Electrochem. Soc. 163 (2016)C240.O Gharbi, N Birbilis, K Ogle, “Li reactivity during the surface pretreatment of Al-Li alloy AA2050-T3”, Electrochim. Acta 243(2017)207-219. Figure 1

Effect of transition oxides on thermal and magnetic properties of phosphate materials

Low melting point glass are attractive industrial materials due to their high thermal and chemical resistance compared to conventional glass. our study aimed to study the influence of transition oxides such as Fe2O3 and Cr2O3 on the thermal and the magnetic properties of glass. The results of differential scanning calorimetry (DSC) have provided a lot of essential information on the correlation between the chemical composition of glass and their characteristic parameters, such as glass transition temperature, crystallization temperature, melting temperature. We have performed the measurement of X-ray diffraction, IR and RAMAN, Mössbauer spectroscopy, as well as the measurements of density, dissolution rate and activation energy of dissolution. The proportion on transition oxides in the sudied glass ensure the glass thermal stability, the relatively low melting temperature, and a high chemical durabilité, with application potential in nuclear waste immobilization.

The Protection of Building Materials of Historical Monuments with Nanoparticle Suspensions

Marble and limestone have been extensively used as building materials in historical monuments. Environmental, physical, chemical and biological factors contribute to stone deterioration. The rehabilitation of stone damage and the delay of further deterioration is of utmost importance. Inorganic nanoparticles having chemical and crystallographic affinity with building materials is very important for the formation of protective coatings or overlayers. In the present work, we have tested the possibility of treating calcitic materials with suspensions of amorphous calcium carbonate (am-CaCO3, ACC) and amorphous silica (AmSiO2). Pentelic marble (PM) was selected as the test material to validate the efficiency of the nanoparticle suspension treatment towards dissolution in undersaturated solutions and slightly acidic pH (6.50). Suspensions of ACC and AnSiO2 nanoparticles were prepared by spontaneous precipitation from supersaturated solutions and by tetraethyl orthosilicate (TEOS) hydrolysis, respectively. The suspensions were quite stable (nine days for ACC and months for AmSiO2). ACC and Am SiO2 particles were deposited on the surface of powdered PM. The rates of dissolution of PM were measured in solutions undersaturated with respect to calcite at a constant pH of 6.50. For specimens treated with ACC and AmSiO2 suspensions, the measured dissolution rates were significantly lower. The extent of the rate of dissolution reduction was higher for AmSiO2 particles on PM. Moreover, application of the nanoparticles on the substrate during their precipitation was most efficient method.

Estimating the activation energy of bond hydrolysis by time-resolved weighing of dissolving crystals

Bond-breaking activation energy EB is nowadays a key parameter for understanding and modeling crystal dissolution processes. However, a methodology to estimate EB based on classical dissolution experiments still does not exist. We developed a new method based on the calibration of a Kossel type dissolution model on measured dissolution rates obtained by mass (or volume) variations over time. The dissolution model does not depend on the geometry of the crystal surface but only on the density of the different types of sites (kink, step, terrace, bulk). The calibration method was applied to different experimental setups (flow through and batch) with different ways of estimating the dissolution rates (solute concentration in the fluid, surface topography) for calcite crystals. Despite the variety of experimental conditions, the estimated bond-breaking activation energies were very close to each other (between 31 and 35 kJ/mol) and in good agreement with ab initio calculations.

Oxidation of V(IV) by Birnessite: Kinetics and Surface Complexation.

Vanadium is a redox-active metal that has been added to the EPA's Contaminant Candidate List with a notification level of 50 μg L-1 due to mounting evidence that VV exposure can lead to adverse health outcomes. Groundwater V concentration exceeds the notification level in many locations, yet geochemical controls on its mobility are poorly understood. Here, we examined the redox interaction between VIV and birnessite (MnO2), a well-characterized oxidant and a scavenger of many trace metals. In our findings, birnessite quickly oxidized sparingly soluble VIV species such as häggite [V2O3(OH)2] into highly mobile and toxic vanadate (HnVO4(3-n)-) in continuously stirred batch reactors under neutral pH conditions. Synchrotron X-ray absorption spectroscopic (XAS) analysis of in situ and ex situ experiments showed that oxidation of VIV occurs in two stages, which are both rapid relative to the measured dissolution rate of the VIV solid. Concomitantly, the reduction of birnessite during VIV oxidation generated soluble MnII, which led to the formation of the MnIII oxyhydroxide feitknechtite (β-MnOOH) upon back-reaction with birnessite. XAS analysis confirmed a bidentate-mononuclear edge-sharing complex formed between VV and birnessite, although retention of VV was minimal relative to the aqueous quantities generated. In summary, we demonstrate that Mn oxides are effective oxidants of VIV in the environment with the potential to increase dissolved V concentrations in aquifers subject to redox oscillations.

Early-Stage Dissolution Kinetics of Silicate-Based Bioactive Glass under Dynamic Conditions: Critical Evaluation.

This manuscript presents a systematic and detailed study of ion release from 45S5 bioactive glass to develop a methodology to directly monitor dissolved ions in a simulated fluid via inductively coupled plasma optical emission spectrometry (ICP OES). For the kinetic study, two dynamic tests, an inline ICP test and a flow-through test, are performed with the same flow rate, temperature, pH, ionic strength of the solution, and sample surface to leaching solution volume ratio. The flow-through test allows for the measurement of an initial dissolution rate, as well the maximum amount of any species released from the surface of the glass. In addition, the data from the inline ICP test are obtained by immediate and direct monitoring of ions from the first minutes of contact of the glass with aqueous fluids with pH values of 4 and 7.4. The overall dissolution rates of the tested commercial bioactive glass in simulated body fluid (SBF) (pH 7.4) were significantly lower compared to the initial rate acquired. The methodology developed in this study can be applied to monitor the controlled release of ions with additional therapeutic functionalities, where the amount of ions released in the first minutes can be critical for the resulting biological performance.

Time-Resolved Measurements of Dissolution Rates of Platinum and Palladium by a Solution Flow Cell Combined with ICP-MS

A time-resolved measurement system, which combined a commercially available solution-flow cell and an inductively coupled plasma mass spectrometer, was established for determining the dissolution rate of platinum (Pt) and palladium (Pd) in this study. The detection limit of the system was successfully improved by thinning the cell channel, and the limits for Pt and Pd were 0.13 pg cm−2 s−1 and 0.39 pg cm−2 s−1, respectively. When the system was applied to Pt and Pd under potential cycling that mimicked the start/stop conditions of a polymer electrolyte fuel cells (PEFCs), it was revealed that the dissolution of Pt and Pd started from a more negative potential than that reported in previous studies. In addition, we succeeded in obtaining time-resolved measurements of the Pt and Pd dissolution rates below the open circuit potential of the PEFCs (approximately 1.0 V) and clarified that the dissolution mechanisms of Pt and Pd were different.

Dissolution Rates of Calcium Boluses and Their Effects on Serum Calcium in Dairy Cattle.

PurposeCalcium supplement boluses vary greatly in content and bioavailability.MethodsIn vivo dissolution and bioavailability studies were conducted to compare commercial calcium supplement boluses with various contents of calcium chloride and calcium carbonate. The products studied included: Bolus 1 (high calcium chloride, no calcium carbonate), Bolus 2 (medium calcium chloride, medium calcium carbonate), and Bolus 3 (low calcium chloride, high calcium carbonate). A bolus was placed in a pre-weighed coarse mesh net for 30, 60, 90, 120, 180, and 240 minutes to measure dissolution rates in the rumen of fistulated animals. To measure calcium uptake, 27 Holstein cows (second and third lactation) were randomly allocated to one of three oral calcium protocols: Treatment 1 (two high calcium chloride boluses at time 0); Treatment 2 (one high calcium chloride bolus at time 0 with a second bolus 12 hours later); or Treatment 3 (two high calcium carbonate boluses at time 0). Treatments were initiated within 12 hours following calving and this was considered time 0.ResultsBolus 1 was the quickest to dissolve (<90 minutes), followed by Bolus 2 (<240 minutes). The high calcium carbonate bolus (Bolus 3) remained after 240 minutes in vivo with a minimum of 75% of the original bolus weight still intact. Cows with severe hypocalcemia (<1.8 mmol/L) responded with a higher serum calcium increase than cows with milder hypocalcemia (>1.8 mmol/L, <2.12 mmol/L). The high calcium carbonate bolus group (Treatment 3) did not show a rapid increase in serum calcium as compared to the high calcium chloride groups (Treatments 1 and 2). The animals receiving Treatment 1 had a greater and more persistent serum calcium response than animals receiving Treatment 2.ConclusionThe study outcome suggests that calcium chloride/calcium sulfate boluses are more effective at generating a serum calcium response than boluses containing high amounts of calcium carbonate and that two boluses administered rapidly after calving may be more effective than the traditional treatment of giving 2 boluses 12 hours apart.

Evaluation of Drug Dissolution Rate in Co-amorphous and Co-crystal Binary Drug Delivery Systems by Thermodynamic and Kinetic Methods

In order to better explain and predict the dissolution characteristics of binary drug delivery systems (BDDSs), the dissolution behaviors of co-crystal (CC) and co-amorphous (CA) systems of sacubitril (SCB) and valsartan (VST) were evaluated in vitro and in vivo by thermodynamic and kinetic methods. The CCs of SCB and VST were prepared into a CA state through rotary evaporation. Solid-state properties were systematically evaluated. Herein, based on the results from previous studies of single-phase systems, we used thermodynamic methods to evaluate the increase in drug dissolution rate after BDDSs change from the crystalline to the amorphous state. After comparing the predicted and measured dissolution rate enhancement of the CC and CA systems, this paper attempts to explain the dissolution rate characteristics of the BDDSs. We then evaluated the bioavailability of two BDDSs in beagle dogs to confirm that there was no discrepancy in vivo with the results obtained in vitro. The results exhibited that there is strong intermolecular interaction between SCB and VST and good physical stability for the CA system. Compared with the CC, the bioavailability of SCB and VST in the CA system increased by 313.9% and 130.5%, respectively. The predicted dissolution rate ratio between CC and CA systems and their actual intrinsic dissolution rates differed by only a factor of 2.5, demonstrating the good correlation between the predicted and measured values. In the future, this method could be expanded to a variety of new samples and exciting drug prospects.