scholarly journals Lead Immobilization and Hydroxamate Ligand Promoted Chloropyromorphite Dissolution

2014 ◽  
Vol 2014 ◽  
pp. 1-10
Author(s):  
Nadia K. Adam
Keyword(s):  
Dissolution Kinetics ◽  
Dissolution Behavior ◽  
Acetohydroxamic Acid ◽  
Model Calculations ◽  
Batch Dissolution ◽  
Phosphate Mineral ◽  
Soils And Sediments ◽  
Lead Release ◽  
Ph Dependent ◽  
Aqueous Complexation

The immobilization of lead, a major environmental contaminant, through phosphate amendments to form the sparingly soluble lead phosphate mineral chloropyromorphite [Pb5(PO4)3] (CPY) is an effective in situ strategy for soil remediation. An important question is the effect of microbial processes on this remediation. Here, we investigate the role of the microbial siderophore ligand desferrioxamine-D1 (DFO-D1) and its analog acetohydroxamic acid (aHA) in CPY lability using pH-dependent batch dissolution kinetics and model calculations. Both (0.01) M aHA and (0.00024) M DFO-D1 are similarly effective and enhance lead release from CPY by more than two orders of magnitude at pH > 6 compared to in the absence of ligands. This is consistent with model calculations of pH-dependent (aqueous) complexation of lead with hydroxamate ligands. More importantly, pH-dependent ligand sorption is predictive of its ligand promoted dissolution behavior. Our results suggest that organic ligands can significantly increase CPY lability at alkaline pHs in soils and sediments and that addition of P amendments to immobilize Pb as CPY may only be successful at acid pHs.

scholarly journals pH-Dependent Solubility and Dissolution Behavior of Carvedilol—Case Example of a Weakly Basic BCS Class II Drug

2015 ◽  
Vol 17 (2) ◽  
pp. 418-426 ◽  
Author(s):  
Rania Hamed ◽  
Areeg Awadallah ◽  
Suhair Sunoqrot ◽  
Ola Tarawneh ◽  
Sami Nazzal ◽  
...  
Keyword(s):  
Class Ii ◽  
Dissolution Behavior ◽  
Bcs Class Ii ◽  
Ph Dependent

Effects of film thickness and alkaline concentration on dissolution kinetics of poly(4-hydroxystyrene) in alkaline aqueous solution

2022 ◽  
Author(s):  
Naoki Tanaka ◽  
Kyoko Matsuoka ◽  
Takahiro KOZAWA ◽  
Takuya Ikeda ◽  
Yoshitaka Komuro ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Film Thickness ◽  
Thick Films ◽  
Dissolution Kinetics ◽  
Dissolution Behavior ◽  
Chemically Amplified ◽  
Fundamental Understanding ◽  
Chemically Amplified Resists ◽  
Kinetics Of ◽  
Simple Combination

Abstract The dissolution behavior of a simple combination of poly(4-hydroxystyrene) (PHS) films and tetramethylammonium hydroxide (TMAH) aqueous solution was analyzed to gain a fundamental understanding of the effects of film thickness and alkaline concentration on the dissolution kinetics of chemically amplified resists (CARs). Films of four different thicknesses, from thick (approximately 900 nm) to thin (approximately 50 nm), were developed in 22 different developers of different concentrations. The dissolution behavior of each combination was observed using a quartz crystal microbalance (QCM). Differences in dissolution kinetics due to film thickness were observed even between relatively thick films such as 900- and 500-nm thick films in dilute developers. These differences were considered to be caused by the diffusion of the solution into the films. Thin films also showed characteristic behavior with dilution. This behavior was due to the interaction between the substrate and the films, unlike in the case of thick films.

scholarly journals Association of trace elements and dissolution rates of soil iron oxides

Soil Research ◽  
2014 ◽  
Vol 52 (1) ◽  
pp. 1 ◽  
Author(s):  
D. Ketrot ◽  
A. Suddhiprakarn ◽  
I. Kheoruenromne ◽  
B. Singh
Keyword(s):  
Trace Elements ◽  
Dissolution Rate ◽  
Significant Proportion ◽  
Dissolution Kinetics ◽  
Major And Trace Elements ◽  
Cube Root ◽  
Fe Oxide ◽  
Fe Oxides ◽  
Batch Dissolution ◽  
Dissolution Behaviour

In this study, nine Oxisols and five Ultisols from Thailand were used to determine the association of major and trace elements with iron (Fe) oxides. The Fe oxides were concentrated and the association of elements (Al, Ca, Cu, Cr, Mg, Mn, Ni, Pb, P, Si, V, Ti, Zn) with Fe was evaluated using batch dissolution in 1 m HCl at 20°C. The dissolution behaviour of Fe oxide concentrates was determined using batch dissolution and flow-through reactors. In addition to Fe, both Al and Ti were present in significant amounts in the Fe oxide concentrates. Manganese was the most abundant trace element, and Cu, Zn, Pb and As concentrations were <250 mg kg–1 in most samples. The dissolution behaviour of Fe-oxide concentrates indicated that Al, Cr and V were mostly substituted for Fe3+ in the structure of goethite and hematite. A significant proportion of Mn, Ni, Co, Pb and Si was also present within the structure of these minerals. Some Mg, Cu, Zn, Ti and Ca was also associated with Fe oxides. The dissolution kinetics of Fe oxide concentrates was well described by three models, i.e. the cube root law, Avrami–Erofejev equation and Kabai equation, with the dissolution rate constants (103k) corresponding to the three models ranging from 0.44 to 6.11 h–1, from 1.01 to 4.40 h–1 and from 0.03 to 4.12 h–1, respectively. The k constants of Fe oxide concentrates in this study were significantly and negatively correlated with the mean crystal dimension derived from [110] and [104] of hematite, the dominant mineral in most samples. The steady-state dissolution rate of a soil Fe-oxide concentrate (sample Kk) was substantially higher than for synthetic goethite under highly acidic conditions; this is possibly due to the greater specific surface area of sample Kk than the synthetic goethite.

Microenvironmental pH-modification to improve dissolution behavior and oral absorption for drugs with pH-dependent solubility

2014 ◽  
Vol 11 (4) ◽  
pp. 505-516 ◽  
Author(s):  
Chika Taniguchi ◽  
Yohei Kawabata ◽  
Koichi Wada ◽  
Shizuo Yamada ◽  
Satomi Onoue
Keyword(s):  
Oral Absorption ◽  
Dissolution Behavior ◽  
Microenvironmental Ph ◽  
Ph Dependent

scholarly journals Dissolution Kinetics of International Simple Glass and Formation of Secondary Phases at Very High Surface Area to Solution Ratio in Young Cement Water

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1254
Author(s):  
Karine Ferrand ◽  
Martina Klinkenberg ◽  
Sébastien Caes ◽  
Jenna Poonoosamy ◽  
Wouter Van Renterghem ◽  
...  
Keyword(s):  
High Surface ◽  
High Surface Area ◽  
Dissolution Kinetics ◽  
Dissolution Behavior ◽  
Secondary Phases ◽  
Residual Rate ◽  
Glass Dissolution ◽  
Ph Decrease ◽  
Kinetics Of ◽  
Very High

Static dissolution experiments were carried out with the reference International Simple Glass under hyperalkaline pH at 70 °C and very high SA/V ratio. Three aspects of glass dissolution behavior were investigated, (1) the rate drop regime and the residual rate (stage II), (2) the formation of secondary phases including thermodynamic aspects, and (3) the microstructure of the interface of altered glass and secondary phases. A very low residual rate of 6 × 10−6 g/m2d was determined based on boron release, which was several orders of magnitude lower than the initial rate established between the start of the experiments and the first sampling on day 59. The presence of a porous layer with a thickness varying between 80 nm and 250 nm and a pore size between 10 nm and 50 nm was observed. CSH phases with a low Ca/Si ratio of 0.3–0.4 and zeolites were also visible at the surface of the altered glass grains, but no glass alteration resumption occurred, probably due to an important pH decrease already at day 59. Thermodynamic calculations assuming congruent glass dissolution and precipitation of the dissolved aqueous species confirmed the precipitation of CSH phases and zeolites.

scholarly journals Ileo-Colon Targeting of the Poorly Water-Soluble Drug Celecoxib Using a pH-Dependent Coating in Combination with Self-Emulsifying Drug Delivery or Solid Dispersion Systems

Pharmaceutics ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 731
Author(s):  
Annemarie Broesder ◽  
Julia M. E. Berends ◽  
Sophie M. Scheepers ◽  
Duong N. Nguyen ◽  
Henderik W. Frijlink ◽  
...  
Keyword(s):  
Drug Delivery ◽  
Solid Dispersion ◽  
Sodium Dodecyl ◽  
Water Soluble ◽  
In Vitro Dissolution ◽  
Dissolution Behavior ◽  
Dispersion Systems ◽  
Precipitation Inhibitor ◽  
Ph Dependent

Targeting celecoxib to the ileo-colonic region could be beneficial for the treatment and prevention of colon cancer. Ileo-colonic targeting can be achieved by using pH-dependent coating systems such as ColoPulse. Celecoxib has poor aqueous solubility, which may jeopardize optimal treatment. Therefore, we combined a pH-dependent coating with self-emulsifying drug delivery systems (SEDDS) or with solid dispersion systems (SD); two approaches that are often used to improve the dissolution behavior of lipophilic drugs. The dissolution behavior of various formulations of both systems was investigated. Optimized formulations with and without precipitation inhibitors were coated with the ColoPulse and the release of celecoxib was tested under non-sink conditions using an in vitro dissolution system, simulating the pH gradient of the gastrointestinal tract. The dissolution behavior of SDs with and without precipitation inhibitor (sodium dodecyl sulfate) and the SEDDS without precipitation inhibitor was negatively impacted by the coating. Control experiments indicated that components of the coating released in the dissolution medium acted as precipitation mediators. However, the SEDDS formulation with HPMC 4000 cps as a precipitation inhibitor showed excellent dissolution behavior. We hypothesize that HPMC accumulates at the oil/water interface of the emulsion thereby stabilizing the emulsion resulting in maintenance of the supersaturated state.

scholarly journals In vitro Comparative Dissolution Studies of Different Propranolol Generic Tablets Available in Bangladesh

2021 ◽  
Vol 11 (6-S) ◽  
pp. 86-91
Author(s):  
Madhabi Lata Shuma ◽  
Bishyajit Kumar Biswas ◽  
Sheikh Zahir Raihan ◽  
Shimul Halder
Keyword(s):  
Release Kinetics ◽  
Dissolution Kinetics ◽  
Heart Rhythm ◽  
The United States ◽  
In Vitro Dissolution ◽  
Dissolution Behavior ◽  
United States Pharmacopoeia ◽  
Model Independent ◽  
Factor Difference

The present study focused to assess in vitro dissolution profiles of four different products of propranolol 10 mg Tablets (Randomly coded as PRP1-PRP4) available in Bangladesh comparing with the reference brand (coded as REF). Propranolol is a competitive non selective beta-adrenergic receptor antagonist used to amend or restore normal heart rhythm in cardiovascular diseases. An in vitro dissolution study was carried out using the United States Pharmacopoeia (USP) paddle method at 75 rpm with 500 mL of 0.1N HCl dissolution media at 37.0± 0.5 0C. All the tested locally manufactured propranolol products; PRP1, PRP2, PRP3, PRP4 showed compatible dissolution (87%, 86%, 87%, and 80%, respectively) pattern (dissolution criterion Q=80% in 30 minutes) compared with the reference brand (88% dissolution in 30 minutes). The dissolution behavior was estimated with the reference brand using a model dependent and model-independent approach (f2>50, f1 < 15).  A mechanistic mathematical release kinetics was also evaluated. The best-fit kinetic model was Hixon-Crowell release kinetics for reference brand and PRP1; and first order release kinetics was predominant for PRP2, PRP3 and PRP4. Keywords: propranolol, dissolution, similarity factor, difference factor, dissolution kinetics

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