Distribution by Scientific Domains
Distribution within Chemistry

Kinds of Dihydrate

  • acetate dihydrate
  • acid dihydrate
  • oxalate dihydrate
  • phosphate dihydrate

  • Selected Abstracts

    Anomalous Spin Transition Observed in Bis(2,6-bis(pyrazol-3-yl)pyridine)iron(II) Thiocyanate Dihydrate,

    A. Bhattacharjee
    Abstract Bis(2,6-bis(pyrazol-3-yl)pyridine)iron(II) thiocyanate dihydrate undergoes a two-step singlet (1A1) , quintet (5T2) transition in which both steps are associated with thermal hysteresis. Thermal cycling of the sample results in its conversion to a second phase which displays a single-step transition with a very narrow hysteresis loop. This second phase slowly reverts to the initial phase on standing at 300 K. The interconversions are completely reversible. The spin state changes have been monitored by measurement of magnetism and Mössbauer spectra and by differential scanning calorimetry (DSC) studies. [source]

    ChemInform Abstract: Stannous Chloride Dihydrate: A Novel and Efficient Catalyst for the Synthesis of gem-Dihydroperoxides from Ketones and Aldehydes.

    CHEMINFORM, Issue 52 2009
    Davood Azarifar
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    Calcium Chloride Rhenate(VII) Dihydrate.

    CHEMINFORM, Issue 48 2007
    Urszula Jarek
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

    ChemInform Abstract: An Unexpected Synthesis of 1H-Perimidine , X-Ray Crystal Structure of 1H-Perimidine Hydrochloride Dihydrate.

    CHEMINFORM, Issue 19 2002
    Seik W. Ng
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

    Non-isothermal Decomposition Reaction Kinetics of the Magnesium Oxalate Dihydrate

    Jian-Jun Zhang
    Abstract The thermal decomposition of the magnesium oxalate dihydrate in a static air atmosphere was investigated by TG-DTG techniques. The intermediate and residue of each decomposition were identified from their TG curve. The kinetic triplet, the activation energy E, the pre-exponential factor A and the mechanism functions f(,) were obtained from analysis of the TG-DTG curves of thermal decomposition of the first stage and the second stage by the Popescu method and the Flynn-Wall-Ozawa method. [source]

    Influence of citric acid on calcium sulfate dihydrate crystallization in aqueous media

    S. Titiz-Sargut
    Abstract The crystallization of Calcium sulfate dihydrate produced by the reaction between pure Ca(OH)2 suspension and H2SO4 solution was investigated at different pH values, temperatures and citric acid concentrations. Crystal size distributions, filtration rates and zeta potentials of gypsum were determined as a function of citric acid concentrations at pH 3.5 and 65°C. The influence of citric acid on the morphology of gypsum was also investigated and discussed. The average particle size of gypsum was reached to maximum in the presence of approximately 2500 ppm citric acid concentration, where the minimum cake resistance and maximum filtration rate were obtained. In the presence of citric acid, various crystal morphologies such as tabular, plate-like, double-taper leaf-like and flower-like, etc., were obtained. The change of morphology is related to the preferential adsorption of citric acid on different crystallographic faces. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Thermal, phase transition and spectral studies in erythromycin pseudopolymorphs: dihydrate and acetone solvate

    Zhanzhong Wang
    Abstract The thermal, phase transition and spectral studies of erythromycin A dihydrate and acetone solvate were performed by Differential Scanning calorimetry (DSC), Thermo Gravimetry (TG-DTA), X-Ray Powder Diffraction (XRPD) and Fourier Transform Infra-Red (FTIR) spectrum. The non-thermal kinetic analysis of erythromycin A dihydrate was carried out by DSC at different heating rates in dynamic nitrogen atmosphere. The result showed that heating rate has substantial influence on the thermal behavior of erythromycin dihydrate. The Arrhenius parameters were estimated according to the Kissinger method. Corresponding to dehydration of dihydrate, melting of dehydrated dihydrate, phase transition from dehydrated dihydrate to anhydrate, and melting of anhydrate, the calculated activation energy were 39.60, 269.85, 261.23, and 582.16 kJmol,1, the pre-exponential factors were 3.46 × 103, 8.06 × 1032, 9.23 × 1030, and 7.29 × 1063 s,1, respectively. Ozawa method was used to compare activation energy values calculated by Kissinger method. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Effect of citric acid and 1,2-dihydroxybenzene 3,5-disulfonic acid on crystallization of calcium sulfate dihydrate under simulated conditions of phosphoric acid production

    M. M. Rashad
    Abstract The effect of citric acid and 1,2-dihydroxybenzene 3,5-disulfonic acid (DHBDSA), as additives, on the crystallization of gypsum was studied under simulated conditions of the of phosphoric acid production. Calcium hydrogen phosphate and sulfuric acid were mixed with dilute phosphoric acid at 80 °C, and the turbidity of the reaction mixture was measured at different time periods to calculate the induction time of gypsum crystals formation. Addition of citric acid increased the induction time and decreased the growth efficiency while addition of DHBDSA decreased the induction time and increased the growth efficiency compared with in absence of additives. The crystals mean and median diameters were found to decrease in the presence of citric acid and increased in the presence of DHBDSA. The surface energy decreased with citric acid and increased with DHBDSA compared to the baseline (without additives). Interestingly, the majority of the formed crystals are tabular with DHBDSA and needle-like type with citric acid and baseline [source]

    Effect of phosphonate additive on crystallization of gypsum in phosphoric and sulfuric acid medium

    H. El-Shall
    Abstract Understanding the mechanisms of growth and inhibition during crystallization of calcium sulfate is of primary importance for many industrial applications. For instance, inhibition of the crystallization process may be required to prevent scale formation in pipes, boilers, heat exchangers, reactors, reverse osmosis membrane surfaces, cooling water systems, secondary oil recovery utilizing water flooding techniques and desalination evaporators, etc. On the other hand, control growth and morphology of gypsum crystals is desired in achieving higher filtration rate and higher productivity of phosphoric acid from phosphate rocks. In this regard, this basic study is carried out to understand effect of Aminotris (methylenephosphonic acid (ATMP) on calcium sulfate dihydrate (gypsum) crystallization. The time elapsed between the achievement of supersaturation and the appearance of a solid phase (termed as induction time) is measured under different supersaturation ratios ranging from 1.018 to 1.979. The data are used to calculate the surface energy, critical nucleus size, and crystal growth rates of gypsum under different conditions. The results show that, the induction time decreases exponentially with increasing the supersaturation ratio. In addition, the surface energy decreases with ATMP compared to the baseline (without ATMP). Interestingly, with addition of the ATMP, the crystals mean and median diameters are found to decrease. The inhibition efficiency ranges from 16% to 59% depending on supersaturation ratio. [source]

    Determination of neutral carbohydrates by CZE with direct UV detection

    ELECTROPHORESIS, Issue 17 2007
    Stella Rovio
    Abstract A new CZE method relying on in-capillary reaction and direct UV detection at the wavelength 270,nm is presented for the simultaneous separation of the neutral carbohydrates xylitol, D -(,)-mannitol, sucrose, D -(+)-fucose, D -(+)-cellobiose, D -(+)-galactose, D -(+)-glucose, L -rhamnose, D -(+)-mannose, D -(,)-arabinose, D -(+)-xylose, and D -(,)-ribose. The alkaline electrolyte solution was prepared of 130,mM sodium hydroxide and 36,mM disodium hydrogen phosphate dihydrate. Separation of the sample mixture was achieved within 35,min. Calibration plots were linear in the range of 0.05,3,mM. Reproducibility of migration times was between 0.3 and 1.1%, and the detection limits for the analytes were 0.02 and 0.05,mM. The optimized method was applied for the determination of neutral monosaccharides in lemon, pineapple, and orange juices and a cognac sample. The methodology is fast since no other sample preparation except dilution is required. [source]

    The Effect of Surface Area and Crystal Structure on the Catalytic Efficiency of Iron(III) Oxide Nanoparticles in Hydrogen Peroxide Decomposition

    Cenek Gregor
    Abstract Iron(II) oxalate dihydrate has been used as a readily decomposable substance for the controlled synthesis of nanosized iron(III) oxides. The polymorphous composition, particle size and surface area of these iron oxide nanoparticles were controlled by varying the reaction temperature between 185 and 500 °C. As-prepared samples were characterized by XRD, low-temperature and in-field Mössbauer spectroscopy, BET surface area and the TEM technique. They were also tested as heterogeneous catalysts in hydrogen peroxide decomposition. At the selected temperatures, the formed nanomaterials did not contain any traces of amorphous phase, which is known to considerably reduce the catalytic efficiency of iron(III) oxide catalysts. As the thickness of the sample (, 2 mm) was above the critical value, a temporary temperature increase ("exo effect") was observed during all quasi-isothermal decompositions studied, irrespective of the reaction temperature. Increasing the reaction temperature resulted in a shift of the exo effect towards shorter times and an increased content of maghemite phase. The maghemite content decreases above 350 °C as a result of a thermally induced polymorphous transition into hematite. The catalytic data demonstrate that the crystal structure of iron(III) oxide (i.e. the relative contents of maghemite and hematite) does not influence the rate of hydrogen peroxide decomposition. However, the rate constant increases monotonously with increasing sample surface area (and decreasing thermolysis temperature), reaching a maximum of 27,×,10,3 min,1(g/L),1 for the sample with a surface area of 285 m2,g,1. This rate constant is currently the highest reported value of all known iron oxide catalytic systems and is even slightly higher than that observed for the most efficient catalyst reported to date, which has a significantly larger surface area of 337 m2,g,1. This surprisingly high catalytic activity at relatively low surface area can be ascribed to the absence of a amorphous phase in the samples prepared in this study. Taking into account these new findings, the contributions of the key factors highlighted above (surface area, particle size, crystal structure, crystallinity) to the overall activity of iron oxides forhydrogen peroxide decomposition are discussed. [source]

    Anion-Directed Template Synthesis and Hydrolysis of Mono-Condensed Schiff Base of 1,3-Pentanediamine and o -Hydroxyacetophenone in NiII and CuII Complexes

    Pampa Mukherjee
    Abstract Bis(o -hydroxyacetophenone)nickel(II) dihydrate, on reaction with 1,3-pentanediamine, yields a bis-chelate complex [NiL2]·2H2O (1) of mono-condensed tridentate Schiff baseligand HL {2-[1-(3-aminopentylimino)ethyl]phenol}. The Schiff base has been freed from the complex by precipitating the NiII as a dimethylglyoximato complex. HL reacts smoothly with Ni(SCN)2·4H2O furnishing the complex [NiL(NCS)] (2) and with CuCl2·2H2O in the presence of NaN3 or NH4SCN producing [CuL(N3)]2 (3) or [CuL(NCS)] (4). On the other hand, upon reaction with Cu(ClO4)2·6H2O and Cu(NO3)2·3H2O, the Schiff base undergoes hydrolysis to yield ternary complexes [Cu(hap)(pn)(H2O)]ClO4 (5) and [Cu(hap)(pn)(H2O)]NO3 (6), respectively (Hhap = o -hydroxyacetophenone and pn = 1,3-pentanediamine). The ligand HL undergoes hydrolysis also on reaction with Ni(ClO4)2·6H2O or Ni(NO3)2·6H2O to yield [Ni(hap)2] (7). The structures of the complexes 2, 3, 5, 6, and 7 have been confirmed by single-crystal X-ray analysis. In complex 2, NiII possesses square-planar geometry, being coordinated by the tridentate mono-negative Schiff base, L and the isothiocyanate group. The coordination environment around CuII in complex 3 is very similar to that in complex 2 but here two units are joined together by end-on, axial-equatorial azide bridges to result in a dimer in which the geometry around CuII is square pyramidal. In both 5 and 6, the CuII atoms display the square-pyramidal environment; the equatorial sites being coordinated by the two amine groups of 1,3-pentanediamine and two oxygen atoms of o -hydroxyacetophenone. The axial site is coordinated by a water molecule. Complex 7 is a square-planar complex with the Ni atom bonded to four oxygen atoms from two hap moieties. The mononuclear units of 2 and dinuclear units of 3 are linked by strong hydrogen bonds to form a one-dimensional network. The mononuclear units of 5 and 6 are joined together to form a dimer by very strong hydrogen bonds through the coordinated water molecule. These dimers are further involved in hydrogen bonding with the respective counteranions to form 2-D net-like open frameworks. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Nitrogen-Rich Compounds of the Lanthanoids: The 5,5,-Azobis[1H -tetrazol-1-ides] of some Yttric Earths (Tb, Dy, Ho, Er, Tm, Yb, and Lu)

    Georg Steinhauser
    Abstract A set of N-rich salts, 3,9, of the heavy lanthanoids (terbium, 3; dysprosium, 4; holmium 5; erbium, 6; thulium, 7; ytterbium, 8; lutetium, 9) based on the energetic 5,5,-azobis[1H -tetrazole] (H2ZT) was synthesized and characterized by elemental analysis, vibrational (IR and Raman) spectroscopy, and X-ray structure determination. The synthesis of the lanthanoid salts 3,9 was performed by crystallization from concentrated aqueous solutions of disodium 5,5,-azobis[1H -tetrazol-1-ide] dihydrate (Na2ZT,2,H2O; 1) and the respective Ln(NO3)3,5,H2O and yielded large rhombic crystals of the type [Ln(H2O)8]2(ZT)3,6,H2O in ca. 70% of the theoretical yield. The compounds 3,9 are isostructural (triclinic space group P) to the previously published yttrium salt 2; they show, however, a clear lanthanoid contraction of several crystallographic parameters, e.g., the cell volume or the LnO bond lengths of the Ln3+ ions and the coordinating H2O molecules. The lanthanoid contraction influences the strengths of the H-bonds, which can be observed as a red shift by 4,cm,1 in the characteristic IR band, in particular from 3595,cm,1 (3) to 3599,cm,1 (9). In good agreement with previous works, 2,9 are purely salt-like compounds without a coordinative bond between the tetrazolide anion and the Ln3+ cation. [source]

    Anomalous Spin Transition Observed in Bis(2,6-bis(pyrazol-3-yl)pyridine)iron(II) Thiocyanate Dihydrate,

    A. Bhattacharjee
    Abstract Bis(2,6-bis(pyrazol-3-yl)pyridine)iron(II) thiocyanate dihydrate undergoes a two-step singlet (1A1) , quintet (5T2) transition in which both steps are associated with thermal hysteresis. Thermal cycling of the sample results in its conversion to a second phase which displays a single-step transition with a very narrow hysteresis loop. This second phase slowly reverts to the initial phase on standing at 300 K. The interconversions are completely reversible. The spin state changes have been monitored by measurement of magnetism and Mössbauer spectra and by differential scanning calorimetry (DSC) studies. [source]

    Desorption kinetics of model polar stratospheric cloud films measured using Fourier Transform Infrared Spectroscopy and Temperature-Programmed Desorption

    Birgit G. Koehler
    This study combines Fourier transform infrared (FTIR) spectroscopy and temperature-programmed desorption to examine the evaporation kinetics of thin films of crystalline nitric acid hydrates, solid amorphous H2O/HNO3 mixtures, H2O,ice, ice coated with HCl, and solid HNO3. IR spectroscopy measured the thickness of each film as it evaporated, either at constant temperature or during a linear temperature ramp (temperature-programmed infrared, TPIR). Simultaneously, a mass spectrometer measured the rate of evaporation directly by monitoring the evolution of the molecules into the gas phase (temperature-programmed desorption, TPD). Both TPIR and TPD data provide a measurement of the desorption rate and yield the activation energy and preexponential factor for desorption. TPD measurements have the advantage of producing many data points but are subject to interference from experimental difficulties such as uneven heating from the edge of a sample and sample-support as well as pumping-speed limitations. TPIR experiments give clean but fewer data points. Evaporation occurred between 170 and 215 K for the various films. Ice evaporates with an activation energy of 12.9 ± 1 kcal/mol and a preexponential factor of 1 × 1032±1.5 molec/cm2 s, in good agreement with the literature. The beta form of nitric acid trihydrate, ,,NAT, has an Edes of 15.6 ± 2 kcal/mol with log A = 34.3 ± 2.3; the alpha form of nitric acid trihydrate, ,,NAT, is around 17.7 ± 3 kcal/mol with log A = 37.2 ± 4. For nitric acid dihydrate, NAD, Edes is 17.3 ± 2 kcal/mol with log A = 35.9 ± 2.6; for nitric acid monohydrate, NAM, Edes is 13 ± 3 kcal/mol with log A = 31.4 ± 3. The ,,NAT converts to ,,NAT during evaporation, and the amorphous solid H2O/HNO3 mixtures crystallize during evaporation. The barrier to evaporation for pure nitric acid is 14.6 ± 3 kcal/mol with log A = 34.4 ± 3. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 295,309, 2001 [source]

    Palladium/Tris(tert -butyl)phosphine-Catalyzed Suzuki Cross- Couplings in the Presence of Water

    Sha Lou
    Abstract Dipalladiumtris(dibenzylideneacetone)/tris(tert -butyl)phosphonium tetrafluoroborate/potassium fluoride dihydrate [Pd2(dba)3/[HP(t- Bu)3]BF4/KF,2,H2O] serves as a mild, robust, and user-friendly method for the efficient Suzuki cross-coupling of a diverse array of aryl and heteroaryl halides with aryl- and heteroarylboronic acids. [source]

    Role of uric acid in different types of calcium oxalate renal calculi

    Aim:, The presence of uric acid in the beginning zone of different types of ,pure' calcium oxalate renal calculi was evaluated with the aim of establishing the degree of participation of uric acid crystals in the formation of such calculi. Methods:, The core or fragment of different types of ,pure' calcium oxalate renal calculi was detached, pulverized and uric acid extracted. Uric acid was determined using a high-performance liquid chromatography/mass spectrometry method. Results:, In calcium oxalate monohydrate (COM) papillary calculi with a core constituted by COM crystals and organic matter, 0.030 ± 0.007% uric acid was found in the core. In COM papillary calculi with a core constituted by hydroxyapatite, 0.031 ± 0.008% uric acid was found in the core. In COM unattached calculi (formed in renal cavities) with the core mainly formed by COM crystals and organic matter, 0.24 ± 0.09% uric acid was found in the core. In COM unattached calculi with the core formed by uric acid identifiable by scanning electron microscopy (SEM) coupled to X-ray microanalysis, 20.8 ± 7.8% uric acid was found in the core. In calcium oxalate dihydrate (COD) unattached calculi containing little amounts of organic matter, 0.012 ± 0.004% uric acid was found. In COD unattached calculi containing little amounts of organic matter and hydroxyapatite, 0.0030 ± 0.0004% of uric acid was found. Conclusions:, From these results it can be deduced that uric acid can play an important role as inducer (heterogeneous nucleant) of COM unattached calculi with the core formed by uric acid identifiable by SEM coupled to X-ray microanalysis (these calculi constitute the 1.2% of all calculi) and in COM unattached calculi with the core mainly formed by COM crystals and organic matter (these calculi constitute the 10.8% of all calculi). [source]

    Urolithiasis in Okinawa, Japan: A relatively high prevalence of uric acid stones

    Abstract Aim:, The aim of the present study was to investigate the composition of urinary tract stones in patients from Okinawa, the most southern island group of Japan. Methods:, The study was conducted by 12 hospitals in Okinawa. A total of 1816 urinary tract calculi were obtained from 1816 patients (1323 males; 493 females). The patients had a mean age of 53 ± 15.3 years (mean ± SD). The calculi were examined to determine their chemical composition. Stone samples were analyzed by computed infrared spectrophotometer. Results:, Pure stones comprised 58.4% of the total, with calcium oxalate stones accounting for 40% (21% monohydrate [whewellite]; 6.6% dihydrate [weddellite]; and 12.4% combined monohydrate and dihydrate stones), uric acid/urate stones for 9.6%, calcium phosphate stones for 5.1%, and struvite stones for 3.7%. The other 41.6% of the stones consisted of calcium oxalate mixed with other components. The male-to-female ratio was 2.7 : 1. Conclusion:, In our series, calcium oxalate stones accounted for 81.6% of the urinary tract calculi, while uric acid/urate stones accounted for 15.8%. Uric acid stones, predominantly the anhydrous and/or dihydrate forms, showed a relatively high prevalence. Calcium oxalate stones, predominantly in the form of whewellite, showed a high prevalence among pure calculi; while the predominant combinations among mixed calculi were weddellite + calcium phosphate and whewellite + uric acid/urate. [source]

    Transformation of 3DP gypsum model to HA by treating in ammonium phosphate solution

    Rungnapa Lowmunkong
    Abstract Three-dimensional printing (3DP) is a CAD/CAM built-up using ink-jet printing technique. Commercially available 3DP system can form only gypsum model and not for bioceramics. On the other hand, transformation of hardened gypsum into hydroxyapatite (HA) by treatment in ammonium phosphate solution was found lately. In the present study, transformation of the 3DP gypsum block to HA was attempted. However, the fabricated 3DP block was soluble in water. To insolubilize, it was heated at 300°C for 10 min, and then, gypsum was transformed to calcium sulfate hemihydrate, CaSO4 · 0.5H2O. The 3D block was immersed in 1M (NH4)3PO4 · 3H2O solution at 80°C for 1,24 h, and the transformation into HA within 4 h was ascertained. A heat-treated plaster of Paris (POP) block was also investigated for comparison. The unheated POP block consisting of gypsum dihydrate took 24 h to complete the transformation, while the heat-treated POP consisting calcium sulfate hemihydrate promoted the transformation into HA; but the transformed thickness in the block was less than the 3DP block. This is probably due to higher solubility of the hemihydrate than gypsum dihydrate. Accelerated transformation of the 3DP block was also caused by its porous structure, which enabled an easy penetration of the phosphate solution. With the present method, it is possible to transform the fabricated gypsum by 3D printing that is adaptive to the osseous defect into HA prostheses or scaffold. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2007 [source]

    Utilization of spent petrochemical sulfuric acid in the production of wet-process phosphoric acid

    Andrzej Chojnacki
    Abstract The possibility of the application of spent sulfuric acid from the petrochemical industry in wet-process phosphoric acid technology was investigated. The effect of organic impurities in sulfuric acid from benzol acidic refining on the solubility of calcium sulfate hydrates is discussed. Solubility isotherms and regression equations for CaSO4,H3PO4,H2SO4,H2O (pure and containing impurities) systems are presented. Phase transition temperatures between dihydrate and hemihydrate calcium sulfate were determined. The difference between pure and polluted sulfuric acid systems observed is negligible over the range of typical wet-process phosphoric acid technology parameters. It is concluded that the application of spent sulfuric acid from benzol acidic refining does not have a negative influence on the crystallization process of dihydrate calcium sulfate and therefore can be applied in wet-process phosphoric acid technology. Copyright © 2005 Society of Chemical Industry [source]


    Currently, hundreds of soybean varieties with a wide range of quality attributes are available. The majority of these soybean varieties have not been evaluated for their quality in soymilk and tofu. In this research, tofu was prepared using the hot ground method by coagulating soymilk from four soybean varieties (Macon, Saturn, OHIOFG1 and OHIOFG2) with calcium sulfate dihydrate. Soybean variety significantly affected yield, held water, color parameters, viscosity, storage modulus, and textural properties of tofu cakes. Soymilk with higher pH, viscosity, and protein produced tofu with higher protein, water held, and yield. Varietal differences should be considered in selecting soybeans for tofu production. Macon soybeans produced the best tofu with regards to quality attributes. [source]

    Crystallization Kinetics and X-ray Diffraction of Crystals Formed in Amorphous Lactose, Trehalose, and Lactose/Trehalose Mixtures

    Song Miao
    ABSTRACT: Effects of storage time and relative humidity on crystallization kinetics and crystal forms produced from freeze-dried amorphous lactose, trehalose, and a lactose/trehalose mixture were compared. Samples were exposed to 4 different relative water vapor pressure (RVP) (44.1%, 54.5%, 65.6%, 76.1%) environments at room temperature. Crystallization was observed from time-dependent loss of sorbed water and increasing intensities of peaks in X-ray diffraction patterns. The rate of crystallization increased with increasing storage humidity. Lactose crystallized as ,-lactose monohydrate, ,-anhydrous, and anhydrous forms of ,- and ,-lactose in molar ratios of 5:3 and 4:1 in lactose and lactose/trehalose systems. Trehalose seemed to crystallize as a mixture of trehalose dihydrate and anhydrate in trehalose and lactose/trehalose systems. The crystal forms in a mixture of lactose and trehalose did not seem to be affected by the component sugars, but crystallization of the component sugars was delayed. Time-dependent crystallization of lactose and trehalose in the lactose-trehalose mixture could be modeled using the Avrami equation. The results indicated that crystallization data are important in modeling of crystallization phenomena and predicting stability of lactose and trehalose-containing food and pharmaceutical materials. Keywords: crystallization, lactose, trehalose, crystal form, X-ray diffraction [source]

    In situ thermo-TOF-SIMS study of thermal decomposition of zinc acetate dihydrate

    Anil Vithal Ghule
    Abstract Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used for an in situ thermal decomposition study of Zn(CH3COO)2·2H2O forming ZnO nanoparticles. TOF-SIMS spectra were recorded at regular temperature intervals of 25 °C in positive and negative detection modes in a dynamic thermal process. Controlled heating (5 °C min,1) of Zn(CH3COO)2·2H2O was also carried out using thermogravimetric analysis (TGA) in an oxygen atmosphere (20 ml min,1). Nearly spherical ZnO nanoparticles with no agglomeration and a narrow size distribution (diameter ,50 nm) were observed, which were characterized using scanning electron microscopy, transmission electron microscopy and x-ray diffraction. In situ thermo-TOF-SIMS was used to monitor the 64Zn+ and 66Zn+ ion abundances as a function of temperature, which showed a similar profile to that observed for weight loss in TGA during decomposition. Based on the experimental results, a possible decomposition mechanism for the formation of ZnO is proposed. Copyright © 2004 John Wiley & Sons, Ltd. [source]

    Evaluation of a rotary tablet press simulator as a tool for the characterization of compaction properties of pharmaceutical products

    F. Michaut
    Abstract The Stylcam 100R, a rotary press simulator, was designed to simulate speed profiles of rotary tablet presses. Such a simulator was qualified by numerous laboratories and, actually, its ability to be used for studying the behaviour of powders under pressure should be examined. Then, the purpose of this work was to investigate the performances of the Stylcam 100R for characterizing the compaction behaviour and the tabletting properties of pharmaceutical powders. The compressibility of three pharmaceutical excipients (microcrystalline cellulose, dicalcium phosphate dihydrate and ,-lactose monohydrate) was studied. Four compression speeds were used on the compaction simulator. Force,displacement cycles were associated with two energy parameters, the specific total energy (Estot) and the specific expansion energy (Esexp). The mean yield pressure was calculated from Heckel's plots obtained with the in-die method. The diametral tensile strength of compacts was measured in order to evaluate mechanical properties. To evaluate the accuracy of all these parameters, a comparative study was carried out on an eccentric instrumented press. The values of energy parameters and tensile strengths of tablets are close between the eccentric press and the compaction simulator, whatever the compression speed on the latter. The mean yield pressure values obtained using the two presses are different. Finally, the Stylcam 100R seems to be a good tool for characterising tabletting properties of powders, except for the Heckel's model probably due to an unadapted equation of deformation and a lack of accuracy of the displacement transducers. Future improvements should allow correcting these two points. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 2874,2885, 2010 [source]

    Process-induced phase transformation of berberine chloride hydrates

    Henry H.Y. Tong
    Abstract Berberine is a natural quaternary ammonium alkaloid used clinically in the chloride salt form for the treatment of diarrhea in many Asian countries. Although the hydrate formation of berberine chloride (BCl) is well documented, the associated mechanism and implications in pharmaceutical formulation have not been studied in detail. In this study, pure BCl dihydrate and BCl tetrahydrate were recrystallized from water and their phase transformation behaviors under defined conditions were investigated. Additionally, pharmacopoeial grade BCl material consisting predominantly of the dihydrate form was examined for potential phase changes when being subjected to a conventional wet granulation procedure for tablet production. Results from solubility measurements, thermal analysis, variable temperature-powder X-ray diffraction (VT-PXRD), and variable temperature-Fourier transform infrared spectroscopy (VT-FTIR) confirmed the solid-state interconversions between the tetrahydrate and dihydrate at 30,49°C and between the dihydrate and anhydrate at 70,87°C. Consistent with the observed phase changes of the two pure hydrates, wet massing of the pharmacopoeial grade BCl sample led to a thermodynamics-driven transition to the tetrahydrate form at room temperature while subsequent tray drying at 50°C caused a reversion back to the dihydrate form. The rate and extent of such hydrate conversion depended largely on the water activity of the granulated powder matrix, which in turn was governed by the particular excipients employed. The present findings have important implications in the regulation of the hydrate forms of BCl in the finished products using specific excipients. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 1942,1954, 2010 [source]

    Solvent-mediated solid phase transformations of carbamazepine: Effects of simulated intestinal fluid and fasted state simulated intestinal fluid

    Paula Lehto
    Abstract Solvent-mediated transformations of carbamazepine (CBZ) anhydrate form III were investigated in Simulated Intestinal Fluid, a simple USP buffer medium, and in FaSSIF, which contains sodium taurocholate (STC) and lecithin, important surfactants that solubilize lipophilic drugs and lipids in the gastrointestinal tract. Raman spectroscopy (in situ) was utilized to reveal the connection between the changes in solid phase composition and dissolution rate while simultaneously detecting the solid state and the dissolved amount of CBZ. Initial dissolution rate was clearly higher in FaSSIF, while the solid phase data revealed that the crystallization of CBZ dihydrate was inhibited in both the dissolution media, albeit by different mechanisms. In SIF this inhibition was related to extensive needle growth, which impeded medium contact with the solid surface by forming a sterical barrier leading to retarded crystallization rates. Morphological changes from the needle-like dihydrate crystals to plate-like counterparts in FaSSIF, combined with the information that the transformation process was leveled off, evidenced strong hydrogen bonding behavior between the CBZ and STC molecules. These results underline the importance of biologically representative dissolution media in linking the in vitro dissolution results of solids that are capable of hydrate formation to their in vivo dissolution behavior. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:985,996, 2009 [source]

    Determination of outer layer and bulk dehydration kinetics of trehalose dihydrate using atomic force microscopy, gravimetric vapour sorption and near infrared spectroscopy

    Matthew D. Jones
    Abstract Knowledge of the kinetics of solid state reactions is important when considering the stability of many medicines. Potentially, such reactions could follow different kinetics on the surface of particles when compared with their interior, yet solid state processes are routinely followed using only bulk characterisation techniques. Atomic force microscopy (AFM) has previously been shown to be a suitable technique for the investigation of surface processes, but has not been combined with bulk techniques in order to analyse surface and bulk kinetics separately. This report therefore describes the investigation of the outer layer and bulk kinetics of the dehydration of trehalose dihydrate at ambient temperature and low humidity, using AFM, dynamic vapour sorption (DVS) and near infrared spectroscopy (NIR). The use of AFM enabled the dehydration kinetics of the outer layers to be determined both directly and from bulk data. There were no significant differences between the outer layer dehydration kinetics determined using these methods. AFM also enabled the bulk-only kinetics to be analysed from the DVS and NIR data. These results suggest that the combination of AFM and bulk characterisation techniques should enable a more complete understanding of the kinetics of certain solid state reactions to be achieved. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:4404,4415, 2008 [source]

    Phase transformation of erythromycin A dihydrate during fluid bed drying

    Meike Römer
    Abstract An in-line near infrared (NIR) spectrometer was employed to monitor phase transformations of erythromycin dihydrate during a miniaturized fluid bed drying process. The pellets, containing 50% (w/w) erythromycin dihydrate and 50% (w/w) microcrystalline cellulose, were dried at 30, 45, and 60°C. Principal component analysis was used to determine solid-state changes. For this purpose the wavelength range of 1360,2000 nm was selected and preprocessed to remove multiplicative effects. Transformation to erythromycin dehydrate was observed for the pellets dried at 45 and 60°C by NIR spectrometry and X-ray powder diffractometry (XRPD). The formation of erythromycin dehydrate was observed at a moisture content 1.4% (w/w) (mass of water per dry mass of sample) while at 1.8% (w/w) neither XRPD nor NIR were able to detect dehydration. Transformation to erythromycin dehydrate therefore depends strongly on the moisture content of the pellets. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:4020,4029, 2008 [source]

    Multivariate chemometric approach to thermal solid-state FT-IR monitoring of pharmaceutical drug compound

    Wei Jian Tan
    Abstract The study of thermal-related solid-state reaction monitored by spectroscopic method needs the use of advanced multivariate chemometric approach. It is because visual inspection of spectral data on particular functional groups or spectral bands is difficult to reveal the complete physical and chemical information. The spectral contributions from various species involved in the solid-state changes are generally highly overlapping and the spectral differences between reactant and product are usually quite minute. In this article, we demonstrate the use of multivariate chemometric approach to resolve the in situ thermal-dependent Fourier-transform infrared (FT-IR) mixture spectra of lisinopril dihydrate when it was heated from 24 to 170°C. The collected FT-IR mixture spectra were first subjected to singular value decomposition (SVD) to obtain the right singular vectors. The right singular vectors were rotated into a set of pure component spectral estimates based on entropy minimization and spectral dissimilarity objective functions. The resulting pure component spectral estimates were then further refined using alternating least squares (ALS). In current study, four pure component spectra, that is, lisinopril dihydrate, monohydrate, anhydrate, and diketopiperazine (DKP) were all resolved and the relative thermal-dependent contributions of each component were also obtained. These relative contributions revealed the critical temperature for each transformation and degradation. This novel approach provides better interpretation of the pathway of dehydration and intramolecular cyclization of lisinopril dihydrate in the solid state. In addition, it can be used to complement the information obtained from differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97: 3379,3387, 2008 [source]

    Qualitative in situ analysis of multiple solid-state forms using spectroscopy and partial least squares discriminant modeling

    Karin Kogermann
    Abstract This study used in situ spectroscopy to reveal the multiple solid-state forms that appear during isothermal dehydration. Hydrate forms of piroxicam and carbamazepine (CBZ) were investigated on hot-stage at different temperatures using near-infrared (NIR) and Raman spectroscopy combined with multivariate modeling. Variable temperature X-ray powder diffraction, differential scanning calorimetry, thermogravimetric analysis, and Karl Fisher titrimetry were used as reference methods. Partial least squares discriminant analysis (PLS-DA) was performed to qualitatively evaluate the phase transition. It was shown that the constructed PLS-DA models, where spectral differences were directly correlated to solid-state modifications, enabled differentiation between the multiple forms. Qualitative analysis revealed that during dehydration, hydrates, such as CBZ dihydrate, may go through several solid-state forms, which must be considered in quantitative model construction. This study demonstrates that in situ analysis can be used to monitor the dehydration and reveal associated solid-state forms prior to quantification. The utility of the complementary spectroscopic techniques, NIR and Raman, have been shown. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 1802,1820, 2007 [source]