Time For Complete Dissolution Research Articles

Modeling of the dissolution phenomena of solid particles into an infinitely large medium from the analytical solutions of reaction–diffusion equations

Mathematical solutions of the concentration of dissolved component in surrounding fluid were obtained for analyses of the dissolution phenomena of spherical, cylindrical, and slab-type particles. Calculation of the surface flux enabled material balance equations to be derived for the prediction of transient particle size. For the spherical particle, the resulting differential equation was solved numerically to compare with the analytical solution. For the cylindrical particle, the Weber transform was applied to predict the radius of the infinitely long cylinder as a function of time. After obtaining an analytical solution for the thickness of the dissolving slab, the result was compared with those of the sphere and cylinder. The spherical particle exhibited the shortest complete dissolution time (CDT), due to having the greatest surface-to-volume ratio. When external film resistance was important for the mass transfer, the Biot number was included in the governing equation, and to predict the particle size during dissolution, the concentration in the fluid phase could be derived by the combination of variables, or the Weber-type transform. When first-order or zero-order reaction occurs in the surrounding fluid, the concentration could also be predicted by the Laplace transform, and the particle size could be calculated for the solid particles. Similar to the simple diffusion process, CDT was predicted to increase in the order sphere < cylinder < slab. The experimental data of the dissolution of polymeric fiber was compared with the modeling result to estimate the diffusivity and solubility factor, which varied with the pH of the surrounding fluid.

Reducing the formation of asphaltene deposits and increasing the flow rates of oil wells

Purpose. Reducing the formation of asphaltene deposits in the bottom-hole zone of wells and increasing their flow rate. Methodology. The purpose of the work is achieved by conducting theoretical and experimental studies on the formation of asphaltene and paraffin deposits in the bottom-hole zone of the oil reservoir and identifying patterns of their dissolution by pumping heated low-boiling oil components containing carbon atoms C6–C9 in molecules into the well. Findings. The experimental studies conducted under laboratory conditions showed high solubility of asphalt-resin and paraffin compounds in low-boiling oil components. To prevent the deposition of asphaltene deposits in the bottom-hole zone of wells, the turbulent nature of oil movement is necessary, which is achieved by increasing reservoir pressure when water or gas is injected into the oil reservoir. It is also necessary to have a reservoir pressure above the saturation pressure of oil with gas. Effective methods are recommended to reduce the formation of asphaltene deposits in the oil reservoir in the bottom-hole zone and to restore the production rates of producing wells by pumping heated low-boiling oil components containing carbon atoms C6–C9 in molecules into the well. It has been experimentally established that when the temperature of the specified solvent changes from 20 to 800 °C, the time of complete dissolution of the asphalt-resin compound (bitumen) in the form of balls with a diameter of 5 mm is within 0.20–3.0 hours, and in reservoir conditions with a temperature of 60–80 °C – significantly less for 0.2–0.25 hours. This indicates that before pumping low-boiling oil components containing C6–C9 carbon atoms in the molecules, they must be preheated to reservoir temperature. A method is also proposed for treating the bottom-hole zone of an oil reservoir with a complex solution including low-boiling oil components containing carbon atoms C6–C9 in molecules, hydrochloric and fluoric acids. Originality. Effective methods are proposed to reduce the formation of asphaltene and paraffin deposits in the bottom-hole zone of the oil reservoir and to restore the production rates of producing wells by pumping heated low-boiling oil components into the well, as well as a complex solution with the inclusion of acids. Practical value. A technique has been developed to improve technological processes to reduce the formation of asphalt-resin-paraffin deposits and to establish rational parameters of the installation for producing low-boiling oil components containing carbon atoms C6–C9 in industrial conditions. Using the results of research in oil fields allows you to restore the initial permeability and thereby increase the flow rate of oil wells by 20–30 %.

Dissolution mechanism of alumina inclusions into CaO–SiO 2 –Al 2 O 3 –Fe t O–MgO slag via a converter tapping process

Reducing the amount of inclusions during the steelmaking process as much as possible and much earlier plays a vital role in improving the quality of steel products. To reveal the dissolution mechanism of inclusions in slag during the converter tapping process, some comparison experiments were conducted by adding isolated spherical alumina balls as inclusions in CaO–SiO2–Al2O3–FetO–MgO slag, and FetO content up to 10% was contained in slag. The results showed that the dissolution rate of alumina balls in the slag was mainly affected by the diffusion of Al2O3, and the diffusion coefficients of Al2O3 were 4.2 × 10–11, 7.5 × 10–11, and 1.5 × 10–10 m2/s at 1500℃, 1550℃, and 1600℃, respectively. In addition, the upgraded diffusion-distance-controlled dissolution model (DDD-Model), in which FetO content was introduced and applied in the study. The results illustrated that the Al2O3 inclusion apparent dissolution rate was improved by a high FetO content, increasing CaO/SiO2 and raising the temperature as soon as possible at the early stage of the converter tapping process. It is not necessary to increase the FetO content in the slag to enhance the dissolution rate of the Al2O3 inclusion at the last tapping stage. The predicted complete dissolution time of spherical Al2O3 inclusions with 1000 µm in diameter based on the upgraded DDD-Model was approximately 1796 s during the actual converter tapping process.

Improvement of the liquid-jet sulfitators construction to increase the efficiency of sulfitation treatment of sugar production liquids

The article discusses and analyzes the construction of liquid-jet sulfitators used in the beet sugar industry. The importance of sulfitation treatment in the sugar beet processing and raw cane sugar technology is noted and the main advantages of its use at various technological stages are given, namely, preparation of extractant used for diffusion sucrose extraction out of beet cossettes, thin juice processing, thick juice with B- and C-remelts processing, as well as raw cane sugar remelt processing. The advantages and disadvantages of liquid-jet sulfitators in comparison with other constructions are noted and criteria for their improvement are given. It has been noted that the created ejection, which sucks in the sulphitation gas into the contacting chamber, and the fact that the absorption of sulfur dioxide occurs on a larger surface than in other types of structures the main advantages of liquid-jet sulphitators. The main disadvantages are the short length of the contacting chamber, which is insufficient for ensuring complete absorption of sulfur dioxide, as well as instability of the generated ejection when the productivity changes. This determines the criteria given in the article for the improvement of liquid-jet sulfitators. The description of the developed construction of the sulphitator centrifugal-jet nozzle of sugar production liquids is given, which provides: the stability of the sulphitation gas supply in a wide range of plant productivity; stability of the hydroaerodynamic regime of the system «treated liquid – sulphitation gas» inside the sulphitator; sufficient contact time for complete dissolution in the treated liquid of the sulfur anhydride contained in the sulphitation gas. The advantages of the developed centrifugal-jet sulfitators in comparison with typical liquid-jet sulfitators are noted: ensuring the operation range of 50-120% of the nominal capacity (plant production capacity); significant reduction in the technical sulfur consumption for the sulphur anhydride production, which is used as a reagent for the sulfitation treatment of liquids in beet sugar processing; reduction of harmful emissions into the atmosphere due to 100 % sulfur anhydride dissolution in the treated liquid.

Stimuli-Responsive Dual Cross-Linked N-Carboxyethylchitosan Hydrogels with Tunable Dissolution Rate.

Here, we discuss the applicability of (methylenebis(salicylaldehyde)—MbSA) for the fabrication of the stimuli-responsive N-carboxyethylchitosan (CEC) hydrogels with a tunable dissolution rate under physiological conditions. In comparison with non-covalent salicylimine hydrogels, MbSA cross-linking via covalent bis(‘imine clip’) and non-covalent hydrophobic interactions allowed the fabrication of hydrogels with storage moduli > 1 kPa at ten-fold lower aldehyde/CEC molar ratio with the preservation of pH- and amino-acid responsive behavior. Although MbSA-cross-linked CEC hydrogels were stable at neutral and weakly alkaline pH, their disassembly in cell growth medium (Dulbecco’s modified Eagle’s medium, DMEM) under physiological conditions was feasible due to transimination reaction with amino acids contained in DMEM. Depending on the cross-linking density, the complete dissolution time of the fabricated hydrogels varied from 28 h to 11 days. The cytotoxicity of MbSA cross-linked CEC hydrogels toward a human colon carcinoma cell line (HCT 116) and primary human dermal fibroblasts (HDF) was remarkably lower in comparison with CEC-salicylimine hydrogels. Fast gelation, relatively low cytotoxicity, and tunable stimuli-induced disassembly under physiological conditions make MbSA cross-linked CEC hydrogels promising for drug encapsulation and release, 3D printing, cell culturing, and other biomedical applications.

Study of the use of compound feeds in the cultivation of koi carp Cyprinus carpio haematopterus

The object of study – koi carp (Cyprinus carpio haematopterus). The aim of this work was the analysis of piscicultural-biological results of growing koi in 2 variants of feed – Coppens and Tetra. During the experiment to determine the water resistance of the granules of the feed, it was established the time of complete dissolution of the feed in the aqueous medium. The leader of the resistance to water was feed Coppens. Feed German company Tetra showed faster solubility than the Dutch product. Fish-breeding and biological indicators of koi carp also had differences in experimental cultivation. The leader in terms of the increase in linear and weight growth was again the feed Coppens (absolute growth was 6.72 g, the average daily increase – 0.22 g). Feed Tetra showed relatively lower results of growth of the studied fish (absolute increase – 5,15 g; average daily increase – 0,17 g). Mass of fish that were fed with Coppens feed has increased by 156%, Tetra – 116%.

The effect of storage at 4°C on canine-specific albumin on product sterility and albumin concentration.

To determine if lyophilized canine-specific albumin (CSA) can be stored beyond the manufacturer recommended 6hours post-reconstitution without significant concern for bacterial growth. Laboratory research. Large private teaching hospital. Six bottles of lyophilized CSA were retrieved from a medical grade (4°C) refrigerator and were reconstituted with 0.9% NaCl to a 5% solution. Time to complete dissolution of all bottles at room temperature without agitation was recorded in minutes. A 1.5-mL sample was collected from each bottle at the following time points: time 0 (at the time of complete dissolution), and then 6, 12, and 24hours after removal from 4°C. Each aliquot was inoculated into a blood culture tube and was immediately submitted for aerobic and anaerobic bacterial culture. A positive and negative control were cultured at the 24-hour time point. At each time point, an additional 0.5-mL aliquot from each albumin bottle was collected, and these were combined to determine the average albumin concentration (g/L, g/dL) as measured by an in-house analyzer. The albumin was stored at 4°C between sample collection. The reconstitution of CSA and storage at 4°C for up to 24hours did not result in anaerobic or aerobic bacterial growth in any of the 24 cultured samples. Storage did not have a clinically significant effect on the albumin concentration of the solution. The average albumin concentration of all samples was 42g/L (4.2g/dL). No growth was noted in the negative control, and the positive control grew 4 strains of bacteria. It appears safe to use lyophilized CSA up to 24hours post-reconstitution without significant risk of bacterial growth or change in albumin concentration.

Evaluation of the Impacts of Formulation Parameters on the Pharmacokinetics and Bioequivalence of Risperidone Orodispersible Film: a Physiologically Based Pharmacokinetic Modeling Approach.

The purpose of this study was to investigate the impacts of the formulation parameters on the pharmacokinetics and bioequivalence of risperidone orodispersible film (ODF) using physiologically based pharmacokinetic model. The pharmacokinetic profiles of two risperidone ODFs, which exhibit different in vitro dissolution, were examined in Beagle dogs after supralingual administration. Subsequently, a physiologically based pharmacokinetic (PBPK) model was constructed to evaluate the in vivo performance of risperidone ODF. The parameter sensitivity analysis (PSA) was used to access the impacts of formulation parameters on the pharmacokinetics of risperidone. Moreover, the validated PBPK model was applied to predict human pharmacokinetic profiles and examine the bioequivalence of these two ODFs. These two ODFs displayed similar risperidone pharmacokinetic profiles in dogs. The parameter sensitivity analysis indicated that the changes in the solubility, particle size, particle density, and diffusion coefficient did not have obvious influence on the in vivo properties of risperidone ODF. Alternation of the in vitro complete dissolution time in water from 15 to 30min led to a 30% decrease in Cmax and 20% of increase in Tmax. AUC0-∞ would be decreased if risperidone was not fully released within 1h. As both ODFs completely released risperidone within 15min, the difference in the extent of in vivo absorption, intestinal regional absorption location, and plasma concentration-time curves between these two ODFs was almost negligible. Consequently, a bioequivalence was foreseen in humans. The in vitro cumulative dissolution percentage in water at 15min was found to be the major determinant on the in vivo properties of risperidone ODF. PBPK modeling appears to be an innovative strategy to guide the development of risperidone ODF.

Effect of Al2O3 Particle Size on Mullite Formation by In-Situ Reaction of Aluminosilicate Castables

The total output of unshaped refractories has been increasing in recent years due to its short production cycle, safety and energy saving, good integrity and so on. Among them, aluminosilicate castables have been widely used. In order to improve the high temperature properties of castable, Al2O3 micro powder and SiO2 micro powder are usually used. However, few researchers have reported the effect of particle size in matrix on in-situ formation of mullite. In this paper, a mass dissolution rate model and a solution nucleation shrinkage model are established based on the control of the rate of in-situ mullite formation, which takes place by the dissolution of Al2O3 to the liquid phase formed by melting of SiO2 powder containing impurities at high temperature.The results show that with the increase of Al2O3 particle size, the mass dissolution rate of independent particles was accelerated, and the nuclear shrinkage rate of Al2O3 particles decreased fastest when the particle size is 1-10μm. The dissolution rate increases with the increase of service temperature. Moreover, the complete dissolution time is shortened with the decrease of particle size of Al2O3. When the particle size is 80μm, it takes 100.31 seconds for a single particle to dissolve completely, but only 1.00 second when the particle size of Al2O3 decreases to 8μm.

Mechanism of enhanced oxidation ability of dilute nitric acid and dissolution of pure gold in seawater with nitric acid

It has been discovered that dilute nitric acid in reversed micelle systems can oxidize the Br- ion to Br2 and we have proposed that the nitryl (or nitronium) ion NO2+ should be the active species in the oxidation process. Nitration of phenol in reversed micelle systems with dilute nitric acid, CHCl3/CTAC/H2O (2.0 mol dm-3 HNO3 in the 1.0% (v/v) H2O phase), has been performed at 35 oC to obtain 2- and 4-nitrophenols, where CTAC represents cetyltrimethylammonium chloride. In aqueous 2.0 mol dm-3 HNO3 solution accompanied by 4.0 mol dm-3 LiCl (and a small amount of LiBr as the bromide resource), trans-1,4-dibromo-2-butene was successfully brominated to 1,2,3,4-tetrabromobutane. This result is good evidence that the Br- ion can be oxidized to Br2 in dilute nitric acid (2.0 mol dm-3) providing it contains concentrated salts. For chloride salts, the cation effects increased as Et4N+ << Na+ < Li+ < Ca2+ < Mg2+. Even the evolution of Cl2 has been demonstrated from < 2.0 mol dm-3 HNO3 solution containing concentrated LiCl, MgCl2, and CaCl2 as well as AlCl3. The dissolution of precious metals (Au, Pt, and Pd), especially, of gold has been demonstrated in 0.1 - 2 mol dm-3 HNO3 accompanied by alkali metal, alkaline earth metal, and aluminum chlorides. The complete dissolution time of pure gold plate (20±2 mg, 0.1 mm thickness) in 2.0 mol dm-3 HNO3 accompanied by 1.0 mol dm-3 AlCl3 has been shortened remarkably with temperature increase from 15 to 80 oC. The dissolution rate constants, log (k /s-1), of a piece of gold wire (19.7±0.5 mg) in 20 mL of 2.0 mol dm-3 HNO3 accompanied by the metal chlorides, in general, increase with increasing salt concentrations at 40 and 60 oC. The gold can be dissolved in the solution of <1.0 mol dm-3 HNO3 and <1.0 mol dm-3 HCl, i.e. a “dilute aqua regia. We have achieved a total dissolution of five pieces of the gold wire (totally 0.10 g) in 100 mL of the 1:1 mixture between seawater and 2.0 mol dm-3 HNO3 at ca. 100 oC.

The effect of lignin on processing and the properties of lignocellulose material recovered by ionic liquid

As a prospective raw material, lignin containing papermaking fibers can be easily recycled, dissolved with proper solvents and reused. However, in order to utilize this material, more eco-friendly green dissolution methods are also required. As a green solvent, ionic liquids (ILs) have been attracted too much interest in processing of lignocellulosic biopolymers, but the practical effect of lignin on this process was not clear. In this due, production of lignocellulosic bio-composite films from bleached (lignin-free) and unbleached (lignin-containing) soda pulps was studied. First, fibers were dissolved in 1-Buthyl 3-Methyl Imidazolium Chloride (BMIMCL) at 85-95 °C. Following fabrication and preparation of the lignocellulosic films, certain mechanical and physical properties of cellulose composite films were analyzed. FESEM and XRD analytical methods were applied to study the product morphology and structure. Microscopic studies showed both fibers were disappeared in the ionic liquid in less than 1 h, although the unbleached fibers took more time for complete dissolution. The results indicated that the films produced from unbleached pulp had less tensile strength and more dynamic contact angle with water droplet than the ones produced from bleached pulp. Moreover, the optical tests revealed that the lignin resulted in less transparency of the films, but increased absorption of UV radiations. This implies that even impure lignocellulose feedstock can have promising features.

Development of new technological solutions for recovery of heavy non­ferrous metals from technogenic waste of electroplating plants and sludge of water treatment systems

In galvanic cakes and municipal wastewater sludge, there are significant amounts of heavy non-ferrous metals, which are classified as hazard class I ecotoxicants and are currently being disposed. The existing methods of toxic waste processing do not provide for the selection and efficient recovery of valuable components. However, the cost of non-ferrous and precious metals and their industrial content in these types of technogenic waste allow justifying the payback and profitability of their industrial processing. Based on the laboratory and large-scale laboratory experiments, flow diagrams of processing of galvanic cakes and wastewater sludge are proposed. The calculated kinetic and thermodynamic characteristics (activation energy, time of complete dissolution, Gibbs free energy value), the recovery parameters of heavy non-ferrous metals (e Cu =99.5 %, e Ni =99.5 %, e Zn =99.9 %) indicate the possibility of industrial implementation of the given flow diagrams. Dependencies of copper recovery on temperature and leaching time are presented. The obtained results allow speaking about the kinetic limitation of the process of galvanic cake leaching (Е Cu =15.7 kJ/mol) and demonstrate the possibility of conducting the process at low temperatures (t=40 o C), which leads to lower energy consumption. The advantage of the proposed options of processing of galvanic cakes and wastewater sludge is the presence of commercial equipment, the use of traditional hydrometallurgical processes, availability and low cost of reactants, short payback periods and anthropogenic load reduction.

Application of Methods of Autoclave Dissolution for Studying Oil Refining Catalysts

Specific features and potentialities of autoclave technologies for decomposition of oil refining catalysts were studied to develop a method for in-process monitoring of changes in the chemical and phase composition of the catalysts. Under autoclave conditions, the time of complete dissolution of oxide phases (hydrotreatment catalysts) was established to shorten from 2 hours to 5–10 min, and the time of platinum opening (reforming catalysts) to be no more than 10 min. In addition, the opening in a closed system prevents from the component loss and from environmental air contamination. It was shown that individual components of the catalysts can be selectively dissolved, isolated and concentrated; the concentrated phases can be used for XPS studies. For example, XPS studies of the dissolved aluminium-containing phase of the spent reforming catalyst revealed the presence of the corundum phase (1,5 %) that indicated the catalyst operation at too high temperatures. A method for estimation of platinum particle size in the catalysts using the quantity of the metal dissolved under the action of chemisorbed oxygen in non-oxidizing acidic media under autoclave conditions was suggested. In the reforming catalysts, the platinum particles were shown to change in size from 4 to 25 nm during operation.

Thermal explosion in a batch reactor charged with a liquid–solid heterogeneous system

The characteristics of a thermal explosion in an ideal mixing batch reactor charged with a liquid–solid heterogeneous system are studied. The reactor initially contains both phases. The solid reagent dissolves and reacts in the liquid phase. A strong dependence of the critical value of the Semenov parameter on the dimensionless time of complete dissolution of the solid reagent is established. It is shown that, at short times of complete dissolution, the critical value of the Semenov parameter is practically independent on this time, and the thermal explosion occurs as in a homogeneous system, according to Semenov theory. The heterogeneous properties of the reaction system manifest themselves only at long times of complete dissolution.

Large carbide dissolution in GCr15 continuously cast billet core

Abstract In-situ tracking was used to evaluate the large carbide dissolution process in GCr15 continuously cast billet core. The time needed to dissolve the large carbides at different temperatures was investigated. As expected, the results showed that increased temperature can significantly shorten the complete dissolution time. Based on the spherical model, a new carbide surface area model to describe carbide size is presented in this paper; the parameters needed were evaluated from the experimental data. Appropriate homogenization cycles are also proposed.

Dissolution of Precipitates During Solution Treatment of Al-Mg-Si-Cu Alloys

A model combining classical diffusion-controlled dissolution equation for a single spherical particle and Johnson–Mehl–Avrami-like equation is used to deal with dissolution process for different kinds of precipitations (Si, Mg2Si, Q(Al1.9Mg4.1Si3.3Cu)) in Al-Mg-Si-Cu alloys. The results reveal that the dissolution time of precipitates increases with increasing their sizes and solute concentrations in the alloy matrix; for the same size and concentration, their dissolution times follow Si > Q(Al1.9Mg4.1Si3.3Cu) > Mg2Si. Two precipitates (Mg2Si and Al1.9Mg4.1Si3.3Cu) with a size of about 700 nm were obtained in a cold rolled Al-Mg-Si-Cu-Zn alloy, and the complete dissolution time is about 15 seconds, which is basically the same as the calculated time by the developed model. The theoretical prediction of dissolution time can be greatly used to design solution treatment and thermomechanical processing parameters of Al-Mg-Si-Cu alloys.

Phosphoric acid-doped organic-inorganic cross-linked sulfonated poly(imide-benzimidazole) for high temperature proton exchange membrane fuel cells

Silane-cross-linked sulfonated poly(imide benzimidazole) (CSiSPIBI) membranes were prepared using γ-(2,3-epoxypropoxy) propyltrimethoxysilane (KH560) as a cross-linker, and the cross-linked structure was characterized using Fourier transform infrared spectroscopy and solubility test. The resulted cross-linked membranes were further doped with phosphoric acid (PA) by means of the acid–base interaction with the alkaline imidazole ring and the electrostatic interaction with siloxane. The results show that PA-doped CSiSPIBI membranes have high proton conductivity due to the formation of a new proton transport pathway between PA and sulfonic acid. Under high temperature and low humidity conditions, the proton conductivity of PA-doped sulfonated membranes is one to two orders of magnitude higher than that of non-PA-doped membranes and PA-doped non-sulfonated membranes. The silane-cross-linked membranes display improved chemical stability and mechanical strength, especially the oxidative stability. The complete dissolution time in Fenton's reagent increases from 510 min for the sulfonated polyimide/polybenzimidazole blend membrane to 1450 min for the silane-cross-linked membrane.

A New Extrudable Form of Hypromellose: AFFINISOL™ HPMC HME.

Hypromellose is a hydrophilic polymer widely used in immediate- and modified-release oral pharmaceutical dosage forms. However, currently available grades of hypromellose are difficult, if not impossible, to process by hot melt extrusion (HME) because of their high glass transition temperature, high melt viscosity, and low degradation temperature. To overcome these challenges, a modified grade of hypromellose, AFFINISOL™ HPMC HME, was recently introduced. It has a significantly lower glass transition temperature and melt viscosity as compared to other available grades of hypromellose. The objective of this paper is to assess the extrudability and performance of AFFINISOL™ HPMC HME (100LV and 4M) as compared to other widely used polymers in HME, including HPMC 2910 100cP (the currently available hypromellose), Soluplus®, Kollidon® VA 64, and EUDRAGIT® E PO. Formulations containing polymer and carbamazepine (CBZ) were extruded on a co-rotating 16-mm twin-screw extruder, and the effect of temperature, screw speed, and feed rate was investigated. The performance of the solid dispersions was evaluated based on Flory-Huggins modeling and characterized by differential scanning calorimetry (DSC), X-ray powder diffraction (XRD), Raman spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and dissolution. All formulations extruded well except for HPMC 2910 100cP, which resulted in over-torqueing the extruder (machine overloading because the motor cannot provide efficient energy to rotate the shaft). Among the HME extrudates, only the EUDRAGIT® E PO formulation was crystalline as confirmed by DSC, XRD, and Raman, which agreed with predictions from Flory-Huggins modeling. Dissolution testing was conducted under both sink and non-sink conditions. Sink dissolution testing in neutral media revealed that amorphous CBZ in the HME extrudates completely dissolved within 15min, which was much more rapid than the time for complete dissolution of bulk CBZ (60min) and EUDRAGIT® E PO solid dispersion (more than 6h). Non-sink dissolution in acidic media testing revealed that only CBZ contained in the AFFINISOL™ HPMC HME, and EUDRAGIT® E PO solid dispersions rapidly supersaturated after 15min, reaching a twofold drug concentration compared to the CBZ equilibrium solubility. In summary, AFFINISOL™ HPMC HME 100LV and AFFINISOL™ HPMC HME 4M are useful in the pharmaceutical HME process to increase wetting and dissolution properties of poorly water-soluble drugs like CBZ.

Agitation Rate and Time for Complete Dissolution in BCS Biowaivers Based on Investigation of a BCS Biowaiver for Dexketoprofen Tablets.

The objective of the present work is to investigate the validity of the existing requirements for BCS biowaivers of immediate release products containing a class I drug in relation to the agitation rate (50 or 75 rpm in the paddle apparatus) and the time limit for complete dissolution (30 min) in the current biowaivers in vitro dissolution tests. Further, the possibility of extensions will be examined since it has been proposed that the time limit for complete dissolution should be revised to 60 min, and also, if cone formation occurs with apparatus 2 at 50 rpm, then a higher agitation rate is acceptable to eliminate it. The development of four generic dexketoprofen immediate release tablets is described. Dexketoprofen is the eutomer of ketoprofen. According to the BCS, dexketoprofen is a class I drug. Three out of the four products failed to show bioequivalence for Cmax in the initial bioequivalence study conducted with the product despite similar but nonrapid dissolution profiles at 50 rpm in the paddle apparatus, or similar and very rapid dissolution profiles at 75 rpm. In conclusion, these data indicate that BCS biowaivers for class I drugs should be granted only when dissolution with the paddle apparatus is complete in 30 min at 50 rpm. The time limit for complete dissolution should not be extended to 60 min. Furthermore, the agitation rate should not be increased to 75 rpm, even in the case of a coning effect.

Can pure gold be dissolved in seawater mixed with aqueous nitric acid?

In order to demonstrate further the oxidation ability of diluted aqueous nitric acid containing abundant amounts of salts, the dissolution of precious metals (Au, Pt, and Pd), especially, of gold has been examined in 0.1–2moldm−3 HNO3 accompanied by alkali metal, alkaline earth metal, and aluminum chlorides. The complete dissolution time of pure gold plate (20±2mg, 0.1mm thickness) in 2.0moldm−3 HNO3 accompanied by 1.0moldm−3 AlCl3 was shortened remarkably with a temperature increase from 15 to 80°C. The dissolution rate constants, log (k/s−1), of a piece of gold wire (19.7±0.5mg) in 20mL of 2.0moldm−3 HNO3 accompanied by the metal chlorides, in general, increase with increasing salt concentrations at 40 and 60°C. For instance, the log (k/s−1) values linearly increase from −4.15 via −3.77, −3.45 to −3.14 by the addition of 1.0., 2.0, 3.0, and 4.0moldm−3 LiCl in a 2.0moldm−3 HNO3 solution at 60°C. The gold can be dissolved in the solution of 1.0moldm−3 HNO3 and 1.0moldm−3 HCl, i.e. a “dilute aqua regia.” We have achieved a total dissolution of five pieces (0.10g) of the gold wire in 100mL of the 1:1 mixture between seawater and 2.0moldm−3 HNO3 at ca. 100°C, with a complete dissolution time of within 17h and log (k/s−1)=−4.52. At 60°C, the complete dissolution experiments of the gold wire in much lower HNO3 concentrations (down to 0.1moldm−3) with the chloride salts have been also successfully performed. The distortion of bulk water and alternation of water properties are discussed based on the Raman spectra with increasing HCl concentrations.