Aqueous Sodium Phosphate Research Articles

Effect of Iodide Ion Concentration on the Physicochemical Properties of Aqueous Sodium Phosphate Solutions as Fertilizer

Effect of Iodide Ion Concentration on the Physicochemical Properties of Aqueous Sodium Phosphate Solutions as Fertilizer

Engineering 3D Printed Scaffolds with Tunable Hydroxyapatite.

Orthopedic and craniofacial surgical procedures require the reconstruction of bone defects caused by trauma, diseases, and tumor resection. Successful bone restoration entails the development and use of bone grafts with structural, functional, and biological features similar to native tissues. Herein, we developed three-dimensional (3D) printed fine-tuned hydroxyapatite (HA) biomimetic bone structures, which can be applied as grafts, by using calcium phosphate cement (CPC) bioink, which is composed of tetracalcium phosphate (TTCP), dicalcium phosphate anhydrous (DCPA), and a liquid [Polyvinyl butyral (PVB) dissolved in ethanol (EtOH)]. The ink was ejected through a high-resolution syringe nozzle (210 µm) at room temperature into three different concentrations (0.01, 0.1, and 0.5) mol/L of the aqueous sodium phosphate dibasic (Na2HPO4) bath that serves as a hardening accelerator for HA formation. Raman spectrometer, X-ray diffraction (XRD), and scanning electron microscopy (SEM) demonstrated the real-time HA formation in (0.01, 0.1, and 0.5) mol/L Na2HPO4 baths. Under those conditions, HA was formed at different amounts, which tuned the scaffolds’ mechanical properties, porosity, and osteoclast activity. Overall, this method may pave the way to engineer 3D bone scaffolds with controlled HA composition and pre-defined properties, which will enhance graft-host integration in various anatomic locations.

Evaluation of butyric acid as a potential supportive treatment in anterior uveitis

Background: The aim of the study was to evaluate the anti-inflammatory effect of topically administered aqueous sodium butyrate solution in an endotoxin-induced uveitis rat model and compare the results with corticosteroid treatment. Material and methods: Forty female Lewis rats were randomly divided into five groups. Uveitis was induced by a single lipopolysaccharide (LPS) injection into each footpad of each LPS+ rat. Group I (naive) received saline injected into the footpad of each rat at a dose of 0.1 mL/each footpad; Group II (LPS+) received saline solution topically. Group III (LPS+ Dex) — an aqueous dexamethasone sodium phosphate solution topically; Group IV (LPS+ But 0.5 mM) — 0.5 mM aqueous sodium butyrate solution topically, Group V (LPS+ But 1 mM) — 1.0 mM aqueous sodium butyrate solution topically. Clinical scoring of inflammation in rat eyes was evaluated before LPS injection and after 24 hours. The iris involvement, posterior synechiae presence, and insight into the eye fundus were clinicallyassessed. A histopathological examination was also performed. The rats were euthanatized 24 hours after LPS injection, and aqueous humor (AqH) was collected from the eyes by anterior chamber puncture. Levels of inflammatory cytokines and chemokines in the AqH were determined with commercially available Luminex assays. Results: Development of iris hyperemia associated with miosis and poor visibility of fundus details occurred 24 hours after LPS injection. Compared to the LPS+ group, the clinical scores were strongly suppressed in rats treated with Dexamethasone and moderately diminished in LPS+ But 0.5 mM. These clinical features were not observed in the controls (Group 1 — naive). Data from inflammatory cytokines evaluation indicates no significant differences between the LPS+ group (Group 2) and the LPS+ But groups (Groups 4 and 5). Histopathological examinations suggest that hyperemia, corneal stratification, and lesions were less common in the group of animals treated with BA in a lower concentration. Conclusion: Topical administration of sodium butyrate as a therapeutic agent might alleviate the severity of intraocular inflammation in eyes with uveitis. The effect of sodium butyrate was slight but clinically significant in 0.5 mM dose, so other doses of topically administered sodium butyrate should be considered and evaluated in further research.

Biofabrication of 3D printed hydroxyapatite composite scaffolds for bone regeneration

Biofabrication has been adapted in engineering patient-specific biosynthetic grafts for bone regeneration. Herein, we developed a three-dimensional (3D) high-resolution, room-temperature printing approach to fabricate osteoconductive scaffolds using calcium phosphate cement (CPC). The non-aqueous CPC bioinks were composed of tetracalcium phosphate, dicalcium phosphate anhydrous, and Polyvinyl butyral (PVB) dissolved in either ethanol (EtOH) or tetrahydrofuran (THF). They were printed in an aqueous sodium phosphate bath, which performs as a hardening accelerator for hydroxyapatite formation and as a retainer for 3D microstructure. The PVB solvents, EtOH or THF, affected differently the slurry rheological properties, scaffold microstructure, mechanical properties, and osteoconductivity. Our proposed approach overcomes limitations of conventional fabrication methods, which require high-temperature (>50 °C), low-resolution (>400 μm) printing with an inadequate amount of large ceramic particles (>35 μm). This proof-of-concept study opens venues in engineering high-resolution, implantable, and osteoconductive scaffolds with predetermined properties for bone regeneration.

Effect of Formulation and Process Parameters on the Disproportionation of Indomethacin Sodium in Buffered Lyophilized Formulations

(i) To investigate buffer salt crystallization and the consequent pH shifts during the freezing stage of the lyophilization of indomethacin sodium (IMCNa) in aqueous sodium phosphate buffer. (ii) To determine the effect of pH shift on the disproportionation of IMCNa in lyophilized formulations. Prelyophilization solutions containing IMCNa in sodium phosphate buffer, at initial buffer concentrations ranging from 10 to 100mM (pH7.0), and at IMCNa concentrations of 5, 10 & 15mg/ml, were investigated. Their phase behavior during cooling was monitored by low temperature X- ray diffractometry (XRD), differential scanning calorimetry (DSC) and pH measurements. The final lyophiles were characterized by infrared spectroscopy (IR) and XRD. Upon cooling to -25°C, pronounced pH shifts were observed only in IMCNa buffered solutions containing high initial buffer concentration (100mM), due to crystallization of Na2HPO4. 12H2O. In the final lyophiles, disproportionation of IMCNa to the free acid (IMC) was observed in systems with buffer concentrations ≥50mM, but not low buffer concentration (10mM). At intermediate buffer concentrations (35 & 20mM) the disproportionation depended on IMCNa concentration. The initial concentrations of both buffer and IMCNa influenced the buffer crystallization. During freeze drying, selective crystallization of a buffer component and the consequent pH shift can cause disproportionation of IMCNa. This can prolong the reconstitution time or retain particles of the poorly soluble free acid in the reconstituted solution.

Interactions of glycine with aqueous solutions of sodium phosphate buffer at T = (288.15, 293.15, 298.15, 303.15, 308.15, 310.15, 313.15, 318.15, 323.15 and 328.15) K: Volumetric and UV absorption studies

Interactions of glycine with sodium phosphate buffer have been investigated by volumetric and UV absorption studies. Densities have been measured for glycine in water of pH=(1.00, 7.40 and 13.40) and in 0.1M, 0.5M and 1M aqueous sodium phosphate buffer (NaPB) solutions as a function of concentration at T=(288.15 to 328.15) K and at pH=(1.00, 7.40 and 13.40) by using digital density meter. Apparent molar volumes (V∅) and partial molar volumes (V2o) obtained from these density data have been used to calculate partial molar volumes of transfer (∆trV2o) from water to aqueous sodium phosphate buffer solutions, which are positive for zwitterionic and deprotonated form of glycine. Interaction coefficients have been obtained from McMillan-Mayer's approach. Effect of temperature on these thermodynamic properties have been studied by determining the partial molar expansibilities (∂V2o/∂T)P at infinite dilution and their second order derivative (∂2V2o/∂T2)P at different temperatures and at pH=(1.00, 7.40 and 13.40). Hydration number (nH) of glycine at pH7.40 have been determined from the V2o data. The results have been rationalized in terms of various interactions taking place in these systems. Further, absorption spectra have also been recorded for the present system with the help of UV–visible spectrophotometer at 298.15K which is helpful in interpreting the possible molecular interactions between glycine and NaPB.

Influence of mixed electrolytes on the adsorption of lysozyme, PEG, and PEGylated lysozyme on a hydrophobic interaction chromatography resin.

In a recent work (Werner A and Hasse H in J Chromatogr A 2013;1315:135) the influence of mixed electrolytes on the adsorption of the macromolecules lysozyme, PEG and di-PEGylated lysozyme on a hydrophobic resin has been studied, but only at one overall ionic strength (3000mM). The present work, therefore, extends these studies to other ionic strengths (2400 and 2700mM), and explores the application of a model to predict the entire data set. The adsorbent is Toyopearl PPG-600M. The solvent is a 25mM aqueous sodium phosphate buffer at pH 7.0. The studied salts are sodium chloride, sodium sulfate, ammonium chloride and ammonium sulfate. Pure salts as well as binary and ternary mixtures of these salts with varying ratios of the amounts of the salts are studied at 25 °C. The loading of the adsorbent increases with increasing salt concentration for all macromolecules. Synergetic effects of the mixed electrolytes are observed. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1104-1115, 2017.

In Operando neutron Imaging of Enzymatic Electrochemical Cells

Enzymatic electrochemical cells (EECs) convert sugars, alcohols, and other fuels into electrical energy through electrochemical reactions catalyzed by naturally occurring enzymes. These devices typically consist of porous carbon electrodes, which may be separated by a polymer membrane. The porous electrodes in EECs are typically saturated with aqueous solutions to support electrochemical activity. The anode contains fuel within the liquid solution, while EECs often incorporate an air-breathing cathode. This work focuses on the characterization of the active anode assembled in a prototype three electrode cell developed to support investigation of the effects of varying environmental conditions on EEC performance. The aluminum three electrode cell reactor was designed and fabricated for in operando neutron imaging. This reactor consisted of two compartments for housing the working and counter electrodes. These halves of the reactor were separated by a Teflon gasket and filter paper. A three electrode cell arrangement was completed by embedding a silver reference electrode in the filter paper. Utilizing neutron tomography the active regions of the three electrode cell were mapped in the absence of the aqueous fuel solution. The reactor was then opened and wetted with a solution of 0.1 M glucose and 0.01 M hydroquinone in an aqueous sodium phosphate buffer. Cyclic voltammetry (CV) was performed to ensure proper function of the cell. Following CV in operando imaging was performed to generate radiographic representations of the anodic components prior to, during, and after discharge. Simultaneous chronoamperometry was performed to provide a connection between the dynamics of the aqueous fuel and buffer solutions and cell performance. Following discharge, tomographic scans were performed to allow for the observation of changes in the active regions of the half-cell. Following the initial measurements the three electrode cell was opened and flushed with fuel solution. The CV, in operando imaging, and tomographic measurements were then repeated. Increased aqueous solution content was found to improve the overall response of the system, yielding higher current in CV and a more consistent discharge behavior during chronoamperometry. Solution content is quantified based on tomographic scans and the related effects on performance are addressed. In general, the studies presented demonstrate a means of controlling test cell geometry to permit the study of EECs using neutron imaging techniques.

Unusual triskelion patterns and dye-labelled GUVs: consequences of the interaction of cholesterol-containing linear-hyperbranched block copolymers with phospholipids.

Cholesterol (Ch) linked to a linear-hyperbranched block copolymer composed of poly(ethylene glycol) (PEG) and poly(glycerol) (hbPG) was investigated for its membrane anchoring properties. Two polyether-based linear-hyperbranched block copolymers with and without a covalently attached rhodamine fluorescence label (Rho) were employed (Ch-PEG30-b-hbPG23 and Ch-PEG30-b-hbPG17-Rho). Compression isotherms of co-spread 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) or 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) with the respective polymers were measured on the Langmuir trough and the morphology development of the liquid-condensed (LC) domains was studied by epi-fluorescence microscopy. LC domains were strongly deformed due to the localization of the polymers at the domain interface, indicating a line activity for both block copolymers. Simultaneously, it was observed that the presence of the fluorescence label significantly influences the domain morphology, the rhodamine labelled polymer showing higher line activity. Adsorption isotherms of the polymers to the water surface or to monolayers of DPPC and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), respectively, were collected. Again the rhodamine labelled polymer showed higher surface activity and a higher affinity for insertion into lipid monolayers, which was negligibly affected when the sub-phase was changed to aqueous sodium chloride solution or phosphate buffer. Calorimetric investigations in bulk confirmed the results found using tensiometry. Confocal laser scanning microscopy (CLSM) of giant unilamellar vesicles (GUVs) also confirmed the polymers' fast adsorption to and insertion into phospholipid membranes.

The evolution of bowel preparation and new developments.

Bowel preparation is essential for successful colonoscopy examination, and the most important factor is the bowel preparation agent used. However, selection of a bowel preparation agent invariably involves compromise. Originally, bowel preparation was performed for radiologic and surgical purposes, when the process involved dietary limitations, cathartics, and enemas, which had many side effects. Development of polyethylene glycol (PEG) solution led to substantive advancement of bowel preparation; however, despite its effectiveness and safety, the large volume involved, and its salty taste and unpleasant odor reduce compliance. Accordingly, modified PEG solutions requiring consumption of lower volumes and sulfate-free solutions were developed. Aqueous sodium phosphate is more effective and better tolerated than PEG solutions; however, fatal complications have occurred due to water and electrolyte shifts. Therefore, aqueous sodium phosphate was withdrawn by the US Food and Drug Administration, and currently, only sodium phosphate tablets remain available. In addition, oral sulfate solution and sodium picosulfate/magnesium citrate are also available, and various studies have reported on adjunctive preparations, such as hyperosmolar or stimulant laxatives, antiemetics, and prokinetics, which are now in various stages of development.

Experimental study and modeling of the influence of mixed electrolytes on adsorption of macromolecules on a hydrophobic resin

The influence of mixed electrolytes on the adsorption of macromolecules on a hydrophobic resin is explored. The macromolecules are native lysozyme, di-PEG-lysozyme-5kDa and pure PEG-6kDa, the adsorbent is Toyopearl PPG-600M, a mildly hydrophobic resin. The solvent is a 25mM aqueous sodium phosphate buffer at pH 7.0 containing additional salts with an overall ionic strength of 3000mM. The studied salts are sodium chloride, ammonium sulfate, sodium sulfate and ammonium chloride. Both pure salts as well as binary and ternary mixtures of these salts with varying ratios of the amounts of the salts are studied. For all solvents adsorption equilibrium isotherms are measured at 25°C. Mixing electrolytes can lead to synergetic effects, i.e. the adsorption in the mixed electrolyte system is sometimes distinctly larger than expected from the results of the single electrolyte systems. The single ions, not the salts, drive the adsorption. A mathematical model is developed, which describes the influence of the different ions and their cross-interactions on the studied adsorption process.

Factors influencing quality of bowel preparation for colonoscopy

Recent technological advances in colonoscopy have led to improvements in both image enhancement and procedural performance. However, the utility of these technological advancements remain dependent on the quality of bowel preparation during colonoscopy. Poor bowel preparation has been shown to be associated with lower quality indicators of colonoscopy performance, such as reduced cecal intubation rates, increased patient discomfort and lower adenoma detection. The most popular bowel preparation regimes currently used are based on either Polyethylene glycol-electrolyte, a non-absorbable solution, or aqueous sodium phosphate, a low-volume hyperosmotic solution. Statements from various international societies and several reviews have suggested that the efficacy of bowel preparation regimes based on both purgatives are similar, although patients' compliance with these regimes may differ somewhat. Many studies have now shown that factors other than the type of bowel preparation regime used, can influence the quality of bowel preparation among adult patients undergoing colonoscopy. These factors can be broadly categorized as either patient-related or procedure-related. Studies from both Asia and the West have identified patient-related factors such as an increased age, male gender, presence of co-morbidity and socio-economic status of patients to be associated with poor bowel preparation among adults undergoing routine out-patient colonoscopy. Additionally, procedure-related factors such as adherence to bowel preparation instructions, timing of bowel purgative administration and appointment waiting times for colonoscopy are recognized to influence the quality of colon cleansing. Knowledge of these factors should aid clinicians in modifying bowel preparation regimes accordingly, such that the quality of colonoscopy performance and delivery of service to patients can be optimised.

Solubility of CO2 in aqueous TSP

The experimental results for CO2 absorption in aqueous tri sodium phosphate (TSP) were presented for total TSP concentrations from 1.0 to 2.0kmol/m3, temperatures from 303.14 to 333.14K and inlet CO2 partial pressures from 10.13 to 20.26kPa. The solubility of CO2 increased with increasing concentrations of TSP from 1.0 to 2.0kmol/m3 at fixed CO2 partial pressure and temperature. Temperature showed positive effect on CO2 solubility and it was increased continuously from 313.14 to 333.14K. The solubility of CO2 also increased slightly with inlet partial pressure of CO2 in the gas stream. The maximum CO2 solubility in TSP was found as 0.960molCO2/mol absorbent at 333.14K and 2.0kmol/m3 TSP concentration. The results of experimental CO2 solubility in aqueous TSP was compared to monoethanol amine (MEA) and other amines mostly used in acid gas treating.

Efficacy and tolerability of split-dose PEG compared with split-dose aqueous sodium phosphate for outpatient colonoscopy: a randomized, controlled trial.

Background and AimsAdequate bowel cleansing is essential for a high-quality, effective, and safe colonoscopy. The aims of this study were to compare the efficacy and tolerability of split-dose polyethylene glycol with aqueous sodium phosphate for outpatients who underwent scheduled colonoscopy.MethodsIn this prospective trial, 207 outpatients (aged between 18 and 65 years, with normal renal function, at low risk for renal damage) were randomized to receive split-dose preparation of PEG (2 L/2 L) (N = 103) or NaP (45 mL/45 mL, 12 h apart) (N = 104) without strict diet restriction the day before colonoscopy. The bowel cleansing efficacy of preparations was rated according to the Ottawa scale and the patient tolerability was assessed using a patient questionnaire.ResultsThere was no significant difference between the two groups for the mean total score using the Ottawa bowel preparation scale (P = 0.181). Significantly greater residual colonic fluid was observed in the split-dose PEG group (1.24 ± 0.49) than in the NaP group (1.04 ± 0.53) (P = 0.007). Patient compliance, preference, and acceptance of a two preparation regimen were similar with no significant differences (P = 0.095, P = 0.280 and P = 0.408, respectively). The overall incidence of adverse events was not significantly different between the two groups; however, the split-dose PEG group tended to have fewer adverse events (52/103 [50.5%], 66/104 [63.5%], P = 0.059) and had significantly less nausea and vomiting (P = 0.036).ConclusionsSplit-dose PEG, compared with split-dose NaP, is associated with more residual colonic fluid, but produces equivalent colon cleansing efficacy and results in less nausea and vomiting, which might improve patient tolerability (clinical trial registration number NCT01229800).

Evaluation of Different Bowel Preparations for Small Bowel Capsule Endoscopy: A Prospective, Randomized, Controlled Study

To obtain an adequate view of the whole small intestine during capsule endoscopy (CE) a clear liquid diet and overnight fasting is recommended. However, intestinal content can hamper vision in spite of these measures. Our aim was to evaluate tolerance and degree of intestinal cleanliness during CE following three types of bowel preparation. This was a prospective, multicenter, randomized, controlled study. Two-hundred ninety-one patients underwent one of the following preparations: 4L of clear liquids (CL) (group A; 92 patients); 90mL of aqueous sodium phosphate (group B; 89 patients); or 4L of a polyethylene glycol electrolyte solution (group C; 92 patients). The degree of cleanliness of the small bowel was classified by blinded examiners according to four categories (excellent, good, fair or poor). The degree of patient satisfaction, gastric and small bowel transit times, and diagnostic yield were measured. The degree of cleanliness did not differ significantly between the groups (P=0.496). Interobserver concordance was fair (k=0.38). No significant differences were detected between the diagnostic yields of the CE (P=0.601). Gastric transit time was 35.7±3.7min (group A), 46.1±8.6min (group B) and 34.6±5.0min (group C) (P=0.417). Small-intestinal transit time was 276.9±10.7min (group A), 249.7±13.1min (group B) and 245.6±11.6min (group C) (P=0.120). CL was the best tolerated preparation. Compliance with the bowel preparation regimen was lowest in group C (P=0.008). A clear liquid diet and overnight fasting is sufficient to achieve an adequate level of cleanliness and is better tolerated by patients than other forms of preparation.

Development of Bacterial Cellulose Nanocomposites

ABSTRACTThe development of synthetic materials with inherent bone properties would allow the safe restoration of bone function and reduce current risks associated with the use of grafts. This study investigated the development of bacterial cellulose–hydroxyapatite composite (CdHA-BC) as a potential bone substitute material. Composites of bacterial cellulose (BC) and oxidized, degradable, cellulose (OBC) were mineralized by sequential incubation in calcium chloride and aqueous sodium phosphate to form a calcium deficient hydroxyapatite (CdHA). The CdHA produced in BC and OBC is similar in morphology and chemistry to the hydroxyapatite found in natural bone. The formation of CdHA is supported by XRD, and EDS results. The CdHA-BC and CdHA-OBC composites degrade in a simulated aqueous physiological environment.

Application of phase optimized liquid chromatography to oligopeptide separations

Stationary phase optimized liquid chromatography (POPLC) has been applied to the separation of oligopeptides. The retention factors and theoretical plate numbers of 13 peptides were determined on five different stationary phases. Based on these values, an optimal stationary phase composition of 250 mm total length consisting of 3 segments of 20 mm octadecyl silica, 10 mm phenyl silica and 220 mm embedded polar octadecyl silica was calculated by the optimizer software. Good agreement between the calculated and experimental chromatograms was observed. In order to achieve short analysis time and baseline separation of all peptides gradient elution and optimization of the column temperature were performed. The optimized mobile phase conditions consisted of (A) acetonitrile and (B) 0.025 M aqueous sodium phosphate buffer, pH 3.0, operated at 10% A (0–12 min) followed by 10–50% A (12–32 min) at a flow rate of 0.5 mL min −1 and column temperature of 35 °C. Using these conditions all peptides could be separated in less than 30 min with good resolution and peak symmetry.

Volumetric and viscosity studies of interactions between sodium phosphate salts and poly(propylene glycol) 400 in aqueous solutions at different temperatures

Density and sound velocity at the 288.15–313.15 K and viscosity at the 298.15–313.15 K temperature range at 5 K intervals for polypropylene glycol (PPG) in aqueous solutions of sodium di-hydrogen phosphate, di-sodium hydrogen phosphate and tri-sodium phosphate with salt mass fractions 0.00, 0.010 and 0.020 are reported at atmospheric pressure. From the experimental density and sound velocity data, the apparent specific volume, excess specific volume, isentropic compressibility and isentropic compressibility deviation values have been determined. The infinite dilution apparent specific volume and isentropic compressibility values of PPG have been obtained and from which the infinite dilution apparent specific volumes of transfer of PPG from water to aqueous sodium phosphate solutions have been obtained for the investigated salt concentrations and temperatures. The excess specific volume, isentropic compressibility and viscosity deviation are negative and decrease in magnitude as temperature, concentration of sodium phosphate and charge on the anion of electrolyte increases.

Phase Transitions in Frozen Systems and During Freeze–Drying: Quantification Using Synchrotron X-Ray Diffractometry

(1) To develop a synchrotron X-ray diffraction (SXRD) method to monitor phase transitions during the entire freeze-drying cycle. Aqueous sodium phosphate buffered glycine solutions with initial glycine to buffer molar ratios of 1:3 (17:50 mM), 1:1 (50 mM) and 3:1 were utilized as model systems. (2) To investigate the effect of initial solute concentration on the crystallization of glycine and phosphate buffer salt during lyophilization. Phosphate buffered glycine solutions were placed in a custom-designed sample cell for freeze-drying. The sample cell, covered with a stainless steel dome with a beryllium window, was placed on a stage capable of controlled cooling and vacuum drying. The samples were cooled to -50 degrees C and annealed at -20 degrees C. They underwent primary drying at -25 degrees C under vacuum until ice sublimation was complete and secondary drying from 0 to 25 degrees C. At different stages of the freeze-drying cycle, the samples were periodically exposed to synchrotron X-ray radiation. An image plate detector was used to obtain time-resolved two-dimensional SXRD patterns. The ice, beta-glycine and DHPD phases were identified based on their unique X-ray peaks. When the solutions were cooled and annealed, ice formation was followed by crystallization of disodium hydrogen phosphate dodecahydrate (DHPD). In the primary drying stage, a significant increase in DHPD crystallization followed by incomplete dehydration to amorphous disodium hydrogen phosphate was evident. Complete dehydration of DHPD occurred during secondary drying. Glycine crystallization was inhibited throughout freeze-drying when the initial buffer concentration (1:3 glycine to buffer) was higher than that of glycine. A high-intensity X-ray diffraction method was developed to monitor the phase transitions during the entire freeze-drying cycle. The high sensitivity of SXRD allowed us to monitor all the crystalline phases simultaneously. While DHPD crystallizes in frozen solution, it dehydrates incompletely during primary drying and completely during secondary drying. The impact of initial solute concentration on the phase composition during the entire freeze-drying cycle was quantified.

Electrophoretic Mobility of Colloidal Gold Particles in Electrolyte Solutions

The electrophoretic mobility of five different-sized spherical colloidal gold particles has been measured in aqueous potassium chloride (KCl) and sodium phosphate electrolyte solutions over the concentration range 0.005-0.154 M solutions. The measured mobilities are independent of electrolyte type and dependent on electrolyte concentration. Interpretation of the mobilities using the simplified electrokinetic formula of Ohshima (J Colloid Interface Sci. 2001, 239, 587-590) indicates that the magnitude of the effective electrokinetic charge density and total charge of particle remains apparently constant with electrolyte concentration. The effective electrokinetic surface charge is negative in KCl and sodium phosphate solutions. The zeta-potential shows a maximum absolute value in both electrolyte solutions (negative).