Comparison of solid-state NMR and isothermal microcalorimetry in the assessment of the amorphous component of lactose

Gustafsson, Christina; Lennholm, Helena; Iversen, Tommy; Nyström, Christer

doi:10.1016/s0378-5173(98)00272-5

Cited by 75 publications

(34 citation statements)

References 22 publications

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“…High-resolution 13 C ss-NMR spectra are obtained using proton decoupling and magic angle spinning (MAS) and sensitivity enhancement is achieved by cross-polarization (CP). 13 C ss-NMR has the advantage of being a nondestructive test method that provides information about the structure of the material (90). Furthermore, one of the advantages of ss-NMR is that it is very sensitive to minor conformational changes but is insensitive to particle size.…”

Section: Ss-nmrmentioning

confidence: 99%

“…In particular, 13 C CPMAS (cross polarization magic angle spinning) appears to be well adapted for studying poly-(or poorly) crystalline solids, revealing qualitative and quantitative features such as identification of phases and structural changes in crystalline polymorphs of pharmaceutical molecules (92)(93)(94). Recently, the development of proper analysis methods to measure relative amorphous and crystalline fractions has raised considerable interest (90,95). Lefort et al (10) have shown, in a study of ball milling trehalose, that an NMR approach can be readily implemented in many situations involving continuous transformations of pure compounds and can still remain a successful method for estimating amorphous content of a sample, even though DSC might fail at it (10).…”

Section: Ss-nmrmentioning

confidence: 99%

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Methods of amorphization and investigation of the amorphous state

Einfalt¹,

Planinšek²,

Hrovat³

2013

Acta Pharmaceutica

117

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.g., polymorphs) provides pharmaceutical scientists with an opportunity to select the preferred form of the material to be used in a formulation. This is very useful since critical properties, such as particle morphology and dissolution properties, are frequently different in the different physical forms of a material. The amorphous form of pharmacologically active materials has received considerable attention because, in theory, it represents the most energetic solid state of a material, and should thus provide the biggest advantages in terms of dissolution rate and bioavailability (1). However, the amorphous form also shows various disadvantages, such as lower physical stability compared to crystals.The structure of an amorphous solid is usually described as possessing a crystal--like short-range molecular arrangement, but lacking a long-range order. As illustrated by Fig. 1, the immediate environment of a molecule (m) in an amorphous solid may not differ significantly from that in a crystal (e.g., similar number of and distance to nearest neighbors), but an amorphous solid lacks any long-range transational-orientational symmetry that characterizes a crystal (1). However, this is only true when we are dealing The amorphous form of pharmaceutical materials represents the most energetic solid state of a material. It provides advantages in terms of dissolution rate and bioavailability. This review presents the methods of solid--state amorphization described in literature (supercooling of liquids, milling, lyophilization, spray drying, dehydration of crystalline hydrates), with the emphasis on milling. Furthermore, we describe how amorphous state of pharmaceuticals differ depending on the method of preparation and how these differences can be screened by a variety of spectroscopic (X-ray powder diffraction, solid state nuclear magnetic resonance, atomic pairwise distribution, infrared spectroscopy, terahertz spectroscopy) and calorimetry methods.

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Section: Ss-nmrmentioning

confidence: 99%

Section: Ss-nmrmentioning

confidence: 99%

Methods of amorphization and investigation of the amorphous state

Einfalt¹,

Planinšek²,

Hrovat³

2013

Acta Pharmaceutica

117

View full text Add to dashboard Cite

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“…Gustafsson et al 10 were able to detect amorphous content as low as 0.5% using NMR and isothermal microcalorimetry. Briggner et al 9 used isothermal microcalorimetry to quantify amorphous content at levels of 1%.…”

Section: Low Level Quantificationmentioning

confidence: 99%

“…Fourier transform infrared (FTIR; mid-infrared) spectroscopy has been applied for determining crystallinity; 4 however, unless attenuated total reflectance sampling is used, significant sample manipulation may be required. Other spectroscopic methods, such as nuclear magnetic resonance (NMR) 10 and Raman spectroscopy, 11 have been investigated recently. No one method can be expected to provide adequate quantification for every material in each application.…”

Section: Introductionmentioning

confidence: 99%

Application of Diffuse Reflectance Near‐Infrared Spectroscopy for Determination of Crystallinity

Seyer

Luner

Kemper

2000

Journal of Pharmaceutical Sciences

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“…8 Water vapor sorption measurements 6 are effective for samples with only 1% amorphous content, however, much attention must be paid to the measurements. 8 Therefore, other techniques such as the use of heat of solution, 6 infrared spectroscopy, 9 and solid-state nuclear magnetic resonance 9,10 are under development. Microcalorimetry has attracted much interest among pharmaceutical researchers recently because it can be used for various preformulation studies, such as those on stability 11±14 and compatibility with excipient.…”

Section: Introductionmentioning

confidence: 99%