Quantitative analyses of complex pharmaceutical mixtures by the Rietveld method

2001 ◽  
Vol 16 (1) ◽  
pp. 20-24 ◽  
Author(s):  
Sampath S. Iyengar ◽  
Neelima V. Phadnis ◽  
Raj Suryanarayanan
Keyword(s):  
Lithium Fluoride ◽  
Goodness Of Fit ◽  
Rietveld Method ◽  
Internal Standard ◽  
Model System ◽  
Analyte Concentration ◽  
Xrd Pattern ◽  
X Ray ◽  
Carbamazepine Dihydrate ◽  
Quantitative Analyses

The object was to perform simultaneous quantitative analyses of complex pharmaceutical solid mixtures by the Rietveld method. Mixtures consisting of anhydrous β-carbamazepine, anhydrous α-carbamazepine, and carbamazepine dihydrate were chosen as the model system. Lithium fluoride was used as the internal standard. Mixtures of various compositions were prepared and subjected to X-ray powder diffractometry (XRD). The XRD pattern of each mixture was analyzed by the Rietveld method and at the end of the refinement, the goodness of fit was evaluated. When the analyte concentration was high (≥20%), the relative error in the determination was <±5%. The detection of analyte was possible even when its concentration was low (<1% w/w). A unique advantage of the method is that it enables simultaneous quantitative analyses of multiple phases without the requirement of “standard curves.” © 2001 International Centre for Diffraction Data.

scholarly journals QUANTIFICAÇÃO DE MULLITA PROVENIENTE DE RESÍDUOS DE CAULIM DA REGIÃO AMAZÔNICA: USO DO MÉTODO DE RIETVELD

Química Nova ◽  
2020 ◽  
Author(s):  
Marlice Martelli ◽  
Eric Mochiutti ◽  
João Lima ◽  
Roberto Neves
Keyword(s):  
Rietveld Method ◽  
Internal Standard ◽  
Amazon Region ◽  
Synthesis Process ◽  
X Ray Diffraction ◽  
Crystalline Phases ◽  
X Ray ◽  
Mineral Phases ◽  
Precursor Material ◽  
Quantitative Analyses

QUANTIFICATION OF MULLITE FROM KAOLIN WASTES FROM THE AMAZON REGION: USE OF THE RIETVELD METHOD. Mullite is used to obtain a refractory material, there are several factors that influence the synthesis process of mullite: the preparation of the mixture, the precipitation and the reaction of SiO2 and Al2O3. For the synthesis of mullite, samples of kaolin processing residues were used as precursor material, because it presents SiO2 and Al2O3 in its composition. This work aimed to identify, by X-ray diffraction, and quantify the mineral phases present in samples of kaolin processing residues from the Amazon region calcined at 1300, 1400 and 1500 ºC, using the Rietveld method. The method allowed the refinement of the complex crystalline structures and was applied to the data supply for quantitative analyses with satisfactory results of good accuracy. The results of the quantification of crystalline and non-crystalline phases (with internal standard) in the samples calcined at 1500 ºC presented approximate values of mullite (62%), cristobalite (32%) and non-crystalline phases (6%), for both samples, indicating that the refinement model applied is optimal. These results obtained from the quantification of the phases by the method of Rietveld are presenting coherent and satisfactory values, in comparison with the theoretical ones by the phase diagram Al2O3 and SiO2

A semi-empirical asymmetry function for X-ray diffraction peak profiles

1995 ◽  
Vol 10 (3) ◽  
pp. 204-206 ◽  
Author(s):  
P. Riello ◽  
P. Canton ◽  
G. Fagherazzi
Keyword(s):  
Goodness Of Fit ◽  
Rietveld Method ◽  
Rietveld Analysis ◽  
Opening Angle ◽  
X Ray Diffraction ◽  
X Ray ◽  
Asymmetry Function ◽  
The Asymmetry ◽  
Fit Index ◽  
Semi Empirical

A new semi-empirical approximation for the asymmetry function to be used in the X-ray Rietveld analysis has resulted in lower values of the so-called goodness-of-fit index, defined as S = Rwp/Rexp, where Rwp is the R-weighted pattern and Rexp is the R-expected [R. A. Young, The Rietveld Method (Oxford U.P., Oxford, 1993)], with respect to the corresponding values obtained with the classical approximation used by Rietveld in his fundamental paper. A comparing test of the two asymmetry functions was carried out for the cubic Y2O3 and for αAl2O3 using either pseudo-Voigt or Pearson VII symmetrical functions and two diffractometers. As in the case of the Rietveld approximation, the present one, which employs an exponential function, is optimized using only one fitting parameter. Experimentally, the asymmetry can be considerably diminished by using Soller slits with a small opening angle (≤2°).

scholarly journals Local-site cation ordering of Ln3+ions in doped PbTiO3

2014 ◽  
Vol 70 (a1) ◽  
pp. C1769-C1769
Author(s):  
Arbelio Madrigal ◽  
Yanela González ◽  
Aime Barranco ◽  
Beatriz Rosabal ◽  
Ernesto Rams ◽  
...  
Keyword(s):  
Rietveld Method ◽  
Calculated Data ◽  
Ferroelectric Material ◽  
High Porosity ◽  
Two Phase ◽  
Xrd Pattern ◽  
X Ray ◽  
Donor And Acceptor ◽  
Ion Substitution ◽  
The Difference

The study of doped PbTiO3 with lanthanide (Ln3+) elements is an alternative way in order to obtain high density samples with near optimal piezoelectric properties, avoiding at the same time a high porosity microstructure and a crystal structure with a large c/a ratio. X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), and scanning electron microscopy experiments were carried out in the (Pb0.88Ln0.08)TiO3 ferroelectric system with a perovskite type structure (Ln = La, Sm; Eu, Gd and Dy). Qualitative EXAFS analysis has shown that Ln ions substitute to Pb2+ and Ti4+ ions at A and B sites of the ABO3 structure, respectively except for La doped PbTiO3. The XRD pattern refinement was consistent with the Ln ion substitution at both A and B sites, which provides the formation of donor and acceptor type defects. The shape of the observed X-ray lines profiles has shown features, which are known for this kind of ferroelectric material to be typical of the ferroelectric domains microstructure. A phenomenological model has been used for fitting the diffraction profiles by the Rietveld method [1]. A two phase model considering isotropic size and anisotropic strain broadening was used as a suitable approximation for describing the peculiar peak shapes of the diffraction pattern[2], resulting in a useful approach for analyzing the effects of the domains microstructure. As example, the figure 1 shows the result of the XRD pattern refinement for the sample (Pb0.88Eu0.08)TiO3 taking into account asymmetric and anisotropic effects [3]. The observed and calculated patterns are denoted with dots and continuous lines, respectively. Bragg reflections are represented by vertical marks. The difference between the observed and the calculated data is plotted at the bottom.

Rietveld-based mineralogical quantitation of deferrified oxisol clays

Soil Research ◽  
2007 ◽  
Vol 45 (3) ◽  
pp. 224 ◽  
Author(s):  
M. E. Alves ◽  
Y. P. Mascarenhas ◽  
D. H. French ◽  
C. P. M. Vaz
Keyword(s):  
Quantitative Analysis ◽  
Management Practices ◽  
Rietveld Method ◽  
Clay Fraction ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
X Ray ◽  
Quantitative Analyses ◽  
Soil Clay ◽  
Derived Data

Although the mineralogical quantitative analysis of the soil clay fraction can provide useful information for the improvement of soil management practices, the quantitation of all clay components normally requires a combination of different analytical techniques, which makes this determination expensive and time-consuming. One alternative for more expeditious mineralogical quantitations consists of using the Rietveld method for the treatment of X-ray diffraction (XRD) data. In this study we evaluate the accuracy of the mineralogical quantitative analyses of oxisol deferrified clays carried out with the application of the Rietveld method to XRD data obtained for both non-spray- and spray-dried samples. Linear regression analyses were carried out for comparing the XRD-Rietveld results with those calculated from X-ray fluorescence spectroscopy (XRF) data. Correspondence was observed between the XRD-Rietveld and XRF-derived data, confirming the potential utility of the Rietveld method for soil clay mineralogical quantitative analysis. Although sample preparation by using the spray drying procedure tended to improve XRD mineralogical quantitation, accurate results can be also achieved when this procedure is not available in the XRD laboratory.

Qualitative and quantitative phase analyses of Pingguo bauxite mineral using X-ray powder diffraction and the Rietveld method

2007 ◽  
Vol 22 (4) ◽  
pp. 300-302 ◽  
Author(s):  
Liangqin Nong ◽  
Xiying Yang ◽  
Lingmin Zeng ◽  
Jingping Liu
Keyword(s):  
Rietveld Refinement ◽  
Phase Analysis ◽  
Powder Diffraction ◽  
Rietveld Method ◽  
X Ray ◽  
Quantitative Phase ◽  
Qualitative And Quantitative ◽  
Refinement Method ◽  
Quantitative Analyses ◽  
Qualitative Phase

X-ray powder diffraction technique and the Rietveld refinement method have been used successfully for the qualitative and quantitative analyses of Pingguo bauxite from Guangxi, China. Qualitative phase analysis shows that the Pingguo bauxite contains diaspore (AlOOH), hematite (Fe2O3), goethite (FeOOH), anatase (TiO2), and kaolinite (Al2(Si2O5)(OH)4). Quantitative Rietveld refinement shows that the weight concentrations of diaspore, goethite, hematite, anatase, and kaolinite for the Pingguo bauxite are 71.9(4)%, 7.0(8)%, 11.3(7)%, 6.5(6)%, and 3.3(9)%, respectively.

Certification of standard reference material 1878b respirable α-quartz

2016 ◽  
Vol 31 (3) ◽  
pp. 211-215 ◽  
Author(s):  
David R. Black ◽  
Marcus H. Mendenhall ◽  
Pamela S. Whitfield ◽  
Donald Windover ◽  
Albert Henins ◽  
...  
Keyword(s):  
Powder Diffraction ◽  
Occupational Safety ◽  
Internal Standard ◽  
Lattice Parameter ◽  
Standard Reference Materials ◽  
Quartz Powder ◽  
Phase Purity ◽  
X Ray ◽  
Safety And Health ◽  
Quantitative Analyses

The National Institute of Standards and Technology (NIST) certifies a suite of Standard Reference Materials (SRMs) to address specific aspects of the performance of X-ray powder diffraction instruments. This report describes SRM 1878b, the third generation of this powder diffraction SRM. SRM 1878b is intended for use in the preparation of calibration standards for the quantitative analyses of α-quartz by X-ray powder diffraction in accordance to National Institute for Occupational Safety and Health Analytical Method 7500, or equivalent. A unit of SRM 1878b consists of approximately 5 g of α-quartz powder bottled in an argon atmosphere. It is certified with respect to crystalline phase purity, or amorphous phase content, and lattice parameter. Neutron powder diffraction, both time of flight and constant wavelength, was used to certify the phase purity using SRM 676a as an internal standard. A NIST-built diffractometer, incorporating many advanced design features was used for certification measurements for lattice parameters.

scholarly journals Rietveld Analysis on X-Ray Diffraction Of South Kalimantan Kaolin Clays

2018 ◽  
Vol 6 (2) ◽  
pp. 171
Author(s):  
Ruliana Febrianti ◽  
Firda Herlina ◽  
Muhammad Saukani
Keyword(s):  
Quantitative Analysis ◽  
Goodness Of Fit ◽  
Least Squares Method ◽  
Rietveld Method ◽  
Rietveld Analysis ◽  
Peak Height ◽  
Peak Position ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Difference

At least 13 million tons of kaolin claystone lie in several regencies of South Kalimantan covering Banjar, Tapin, Hulu Sungai Utara and Kotabaru regencies. This paper reports an attempt to explore their crystalline state characteristics, projecting their potential use for geopolymer. Sungai Tabuk, Cintapuri and Tatakan, due to their largest kaolin claystone deposits, were chosen as the sampling sites. The kaolin samples were prepared by syphoning method prior to X-ray diffraction (XRD) characterizations in determining their crystalline phases. X’Pert HighScore Plus and Rietica software were respectively responsible for the qualitative and quantitative phase analyses. The qualitative analysis used search and match method at peak position and peak height between measured and calculated diffraction patterns. Our study revealed the existence of two main phases in the sample, i.e. quartz (SiO2) and kaolinite (Al2Si2O5(OH)4). In addition, the Quantitative analysis used the Rietveld method with the least squares method approach. Rietveld refinement was based on a goodness of fit score of less than 4% by minimizing the difference in the character of the diffraction pattern (position, height, width and peak shape) between the observed and the calculated XRD patterns. The Rietveld quantitative analysis shows, Tatakan is an area with kaolinite-richest deposit (±84%), followed by Cintapuri (±76%) and Tabuk (±70%); quartz is found in reverse.

Structure Re-determination of LASSBio-294 – a cardioactive compound of the N-acylhydrazone class – using X-ray powder diffraction data

2013 ◽  
Vol 28 (S2) ◽  
pp. S491-S509 ◽  
Author(s):  
Fanny N. Costa ◽  
Fabio Furlan Ferreira ◽  
Tiago F. da Silva ◽  
Eliezer J. Barreiro ◽  
Lídia M. Lima ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Goodness Of Fit ◽  
Rietveld Method ◽  
Therapeutic Interventions ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Cell Parameters

Many N-acylhydrazone derivatives synthetized in LASSBio® cannot be prepared as single crystals of sufficient size and/or quality for structure determination to be carried out using single crystal X-ray diffraction techniques. This article highlights the opportunity for determining crystal structures of this class of compounds directly from powder diffraction data. For this task, the crystal structure of LASSBio-294 was re-determined by means of conventional X-ray powder diffraction data and so, compared with the crystal structure already determined for single crystal data. LASSBio-294 is a cardioactive compound of the N-acylhydrazone class, which can become part of the therapeutic interventions designed to decrease exertional fatigue, and, consequently, improve the quality of life of patients suffering from chronic heart failure. Its final crystal structure was refined by means of the Rietveld method (Rietveld, 1967; 1969). This drug crystallizes in a monoclinic (P21/c) space group, with unit cell parameters a = 11.3413(3) Å, b = 12.3573(4) Å, c = 9.0158(3) Å, β = 89.821(2)°, V = 1263.55(7) Å3, Z = 4, Ź = 1 and ρcalc = 1.4419(1) g cm−3. The goodness-of-fit indicator and R-factors were, respectively: χ2 = 1.203, RBragg = 0.696%, Rwp = 5.59%, Rexp = 4.65% and Rp = 4.18%. The molecules in LASSBio-294 are H-bonded along the c-axis involving the atoms N(3)–H(8)···O(4).

Quantitative X-Ray Diffraction Analysis of Anhydrous and Hydrated Portland Cement - Part 2: Computer-Based Methods

2015 ◽  
Vol 1087 ◽  
pp. 498-503 ◽  
Author(s):  
Duong D. Nguyen ◽  
Liam Devlin ◽  
Pramod Koshy ◽  
Charles C. Sorrell
Keyword(s):  
Portland Cement ◽  
Rietveld Method ◽  
Internal Standard ◽  
Xrd Analysis ◽  
Internal Standard Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
External Standard ◽  
Computer Based ◽  
General Aspects

The present work reviews current practices in quantitative XRD analysis of anhydrous and hydrated Portland cement. While Part 1 of this two-part work reviews the conventional internal standard method and the reference intensity ratio (RIR) method, Part 2 reviews the more commonly used computer-based methods, which include the Rietveld method (with or without internal standard) and the G-factor method (with external standard). Further, some critical general aspects of the experimental procedures that affect the accuracy of the analysis are discussed.

The Application of X-Ray Diffraction for Glass Batch Homogeneity Determination

1981 ◽  
Vol 25 ◽  
pp. 379-382
Author(s):  
H. S. Kim ◽  
C. I. Cohen
Keyword(s):  
Sample Preparation ◽  
Glass Batch ◽  
Reference Sample ◽  
Internal Standard ◽  
Data Sets ◽  
Internal Standard Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Integrated Intensity ◽  
Quantitative Analyses

AbstractAn X-ray diffraction (XRD) technique is employed to determine the presence or absence of crystalline phases in glass batch and to determine its homogeneity qualitatively and quantitatively.Sample preparation problems are discussed, and promising techniques for sample preparation are presented. Qualitative batch homogeneity determination is accomplished by comparing the integrated intensity of a particular reflection of the reference sample to that of the unknown sample. Quantitative batch determination is accomplished by using the internal standard method. Three replicated data sets indicate that the standard deviation of kaolinite and colemanite are higher than those of quartz and calcite. However, the overall data from the quantitative analyses lie within an acceptable range of precision and accuracy.

Sign in / Sign up

Export Citation Format

Share Document