Accurate quantification of quartz and other phases by powder X-ray diffractometry

Hurst, Vernon J.; Schroeder, Paul A.; Styron, Robert W.

doi:10.1016/s0003-2670(96)00425-4

Cited by 55 publications

(22 citation statements)

References 12 publications

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“…Nonetheless, there are differences in the locations and intensities of the weak peaks. Some of those differences can most likely be attributed to preferred orientation (19)(20)(21)(22). Photomicrographs of lots A-D (Fig.…”

Section: Comparison Of Analytical Techniquesmentioning

confidence: 99%

Investigating Gabapentin Polymorphism Using Solid-State NMR Spectroscopy

et al. 2012

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Abstract. Solid-state NMR spectroscopy (SSNMR), coupled with powder X-ray diffraction (PXRD), was used to identify the physical forms of gabapentin in samples prepared by recrystallization, spray drying, dehydration, and milling. Four different crystalline forms of gabapentin were observed: form I, a monohydrate, form II, the most stable at ambient conditions, form III, produced by either recrystallization or milling, and an isomorphous desolvate produced from desolvating the monohydrate. As-received gabapentin (form II) was ball-milled for 45 min in both the presence and absence of hydroxypropylcellulose (HPC). The samples were then stored for 2 days at 50°C under 0% relative humidity and analyzed by 13 C SSNMR and PXRD. High-performance liquid chromatography was run on the samples to determine the amount of degradation product formed before and after storage. The 1 H T 1 values measured for the sample varied from 130 s for the as-received unstressed material without HPC to 11 s for the material that had been ball-milled in the presence of HPC. Samples with longer 1 H T 1 values were substantially more stable than samples that had shorter T 1 values. Samples milled with HPC had detectable form III crystals as well. These results suggest that SSNMR can be used to predict gabapentin stability in formulated products.

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Section: Comparison Of Analytical Techniquesmentioning

confidence: 99%

Investigating Gabapentin Polymorphism Using Solid-State NMR Spectroscopy

et al. 2012

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“…Details of these methods are presented in Table 7. Although IR is less specific than XRD (IR methods cannot readily distinguish crystalline silica polymorphs), the technique is less expensive and can be optimized for measuring quartz in well-defined sample matrices [Madsen et al 1995;Smith 1997;Hurst et al 1997]. Samples that contain other silicates (such as kaolinite) and amorphous silica can present interferences in the analyses.…”

Section: Ir Spectrometrymentioning

confidence: 99%

Summary of Notifiable Noninfectious Conditions and Disease Outbreaks: Surveillance for Silicosis — Michigan and New Jersey, 2003–2010

Filios

Mazurek²,

Schleiff³

et al. 2015

MMWR Morb. Mortal. Wkly. Rep.

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“…As one of the goals for this study was the identification of the different crystal structures, our predominant interest was the position of the x-ray reflections. The difference in the sample environment between DSC and XRPD might be responsible for the minor difference at what temperature the dehydration started 14 (see section 3.4 and Figure 3). The DSC measurements were made in sealed pans, while the x-ray measurements were made in an open sample holder.…”

Section: Visual Characterization Of β-Sitosterol Crystals During Heatingmentioning

confidence: 99%

Physical changes of β-sitosterol crystals in oily suspensions during heating

et al. 2005

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The aim of this research was to describe the thermal behavior of β-sitosterol crystals in oil-suspensions with a focus on the role of water during heating. The suspensions were prepared by recrystallization in order to achieve a microcrystalline particle size. The structural changes together with the mechanical properties of the suspensions during heating were studied by using variable temperature X-ray powder diffractometry (VT-XRPD), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). Hydrated β-sitosterol crystals in an oil-suspension dehydrated, despite the composition of the suspensions, at low temperatures. At high β-sitosterol concentration, the monohydrate crystal form changed partially to a hemihydrated form, and when only a small amount of water was initially incorporated, the hemihydrate crystal form dehydrated to a mostly anhydrate crystal form. The released water, which was immiscible in the surrounding oil, caused the recrystallization of hydrated β-sitosterol during cooling. This procedure indicated a reversible dehydration process. Structural and thermal analysis of β-sitosterol crystals in suspensions, together with mechanical analysis made it possible to understand various physical changes during heating.

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Accurate quantification of quartz and other phases by powder X-ray diffractometry

Cited by 55 publications

References 12 publications

Investigating Gabapentin Polymorphism Using Solid-State NMR Spectroscopy

Investigating Gabapentin Polymorphism Using Solid-State NMR Spectroscopy

Summary of Notifiable Noninfectious Conditions and Disease Outbreaks: Surveillance for Silicosis — Michigan and New Jersey, 2003–2010

Physical changes of β-sitosterol crystals in oily suspensions during heating

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