Outcomes of the International Union of Crystallography Commission on Powder Diffraction Round Robin on Quantitative Phase Analysis: samples 2, 3, 4, synthetic bauxite, natural granodiorite and pharmaceuticals

Abstract

The International Union of Crystallography (IUCr) Commission on Powder Diffraction (CPD) has sponsored a round robin on the determination of quantitative phase abundance from diffraction data. The aims of the round robin have been detailed by Madsen et al. [J. Appl. Cryst. (2001), 34, 409±426]. In summary, they were (i) to document the methods and strategies commonly employed in quantitative phases analysis (QPA), especially those involving powder diffraction, (ii) to assess levels of accuracy, precision and lower limits of detection, (iii) to identify speci®c problem areas and develop practical solutions, (iv) to formulate recommended procedures for QPA using diffraction data, and (v) to create a standard set of samples for future reference. The ®rst paper (Madsen et al., 2001) covered the results of sample 1 (a simple three-phase mixture of corundum,¯uorite and zincite). The remaining samples used in the round robin covered a wide range of analytical complexity, and presented a series of different problems to the analysts. These problems included preferred orientation (sample 2), the analysis of amorphous content (sample 3), microabsorption (sample 4), complex synthetic and natural mineral suites, along with pharmaceutical mixtures with and without an amorphous component. This paper forms the second part of the round-robin study and reports the results of samples 2 (corundum,¯uorite, zincite, brucite), 3 (corundum,¯uorite, zincite, silica¯our) and 4 (corundum, magnetite, zircon), synthetic bauxite, natural granodiorite and the synthetic pharmaceutical mixtures (mannitol, nizatidine, valine, sucrose, starch). The outcomes of this second part of the round robin support the ®ndings of the initial study. The presence of increased analytical problems within these samples has only served to exacerbate the dif®culties experienced by many operators with the sample 1 suite. The major dif®culties are caused by lack of operator expertise, which becomes more apparent with these more complex samples. Some of these samples also introduced the requirement for skill and judgement in sample preparation techniques. This second part of the round robin concluded that the greatest physical obstacle to accurate QPA for X-ray based methods is the presence of absorption contrast between phases (microabsorption), which may prove to be insurmountable in some circumstances.

Application of a New Method in Identifying the Sludge Deposits from Refineries and Gas Plants: A Case of Laboratory-Based Study

“…In this article, the authors used the software package PANalytical High Score Plus (X'Pert High Score Plus Version 2.2c PANalytical Inc.), combined with the ICDD of the PDF-4+ database of the standard reference materials to determine the phase identification of the XRD data of the crystalline materials at the treated sludge samples. Subsequently, the Rietveld method was used to refine whole XRD patterns for the phase composition analysis [14][15][16][17] (i.e., wt% for each of the identified phases). The parameters refined for the random orientation of crystallites were the same as those described by Sitepu et al [12].…”

“…If the sample preparation is taken with great care, XRD provides accurate information on phase identification [8], Figure 2(b). When all the phases are identified accurately, the Rietveld method [9][10][11] can be used to perform the crystal structures [12], crystallographic preferred orientations [13], and quantitative phase analysis [14][15][16][17] of XRD data of crystalline materials. Additionally, the other structural parameters, such as average grain size, crystallinity, strain, and crystal defects can also be determined if they are required.…”

Analyse ved røntgendiffraktion - Rietveld-metoden

“…Endvidere blev der lavet en raekke blandinger af standardprøverne. "Monomineralerne" var følgende: Anhydrit, CaSO 4 …”

Clínqueres Pórtland Belíticos. Síntesis y Análisis Mineralógico

“…On the other hand, a combination of Rietveld methodology (10) and X-ray powder diffraction (XRPD) is the most efficient tool for the quantitative phase analysis (QPA) of mixtures of crystalline substances (11,12). This approach uses no standard, but requires the prior knowledge of the crystal structures of all the phases present as it involves comparing a theoretical XRD pattern -obtained from the crystal structures-and the experimental one, provided by the diffractometer.…”