Correction of the Effect of Particle Shape on the size distribution measured with a laser diffraction instrument

Heffels, Camiel; Verheijen, P.J.T.; Heitzmann, Daniel; Scarlett, B. Florence

doi:10.1002/ppsc.19960130504

Cited by 28 publications

(16 citation statements)

References 5 publications

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“…When the particle shape deviates from a sphere, a single index such as a diameter is no longer representative. Investigators have proposed that it is possible to deconvolute the particle size and shape information obtained by laser diffraction 7–11. This a daunting task when considering the computer codes used for laser diffraction instruments are confidential, a variety of light sources and detector arrays are used to gather the scattered light, and no single solution exists for all instruments.…”

Section: Physical Properties For Drug Substance Characterizationmentioning

confidence: 99%

“…Two schools of thought have developed around this topic: one is to try to understand the impact of particle shape on laser diffraction measurements, while the other is to select alternate particle sizing techniques that are better equipped to deal with both particle size and shape. Investigators have proposed that it is possible to deconvolute the particle size and shape information obtained by laser diffraction 7–9, 24, 25. This is a daunting task considering the computer codes used for laser diffraction instruments are proprietary, a variety of light sources and detector arrays are used to gather the scattered light, and no single solution exists for all instruments.…”

Section: Physical Properties For Drug Substance Characterizationmentioning

confidence: 99%

See 1 more Smart Citation

Particle engineering: A strategy for establishing drug substance physical property specifications during small molecule development

Iacocca

Burcham

Hilden

2010

Journal of Pharmaceutical Sciences

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Section: Physical Properties For Drug Substance Characterizationmentioning

confidence: 99%

Section: Physical Properties For Drug Substance Characterizationmentioning

confidence: 99%

Particle engineering: A strategy for establishing drug substance physical property specifications during small molecule development

Iacocca

Burcham

Hilden

2010

Journal of Pharmaceutical Sciences

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“… Muhlenweg and Hirleman [1998] also used a similar approach. Probably the most detailed shape‐related calculations suitable for this method were performed by Heffels et al [1996]. The shapes included rods, prisms, and crystalline shapes.…”

Section: Introductionmentioning

confidence: 99%

Light scattering by random shaped particles and consequences on measuring suspended sediments by laser diffraction

Agrawal¹,

Whitmire²,

Mikkelsen³

et al. 2008

J. Geophys. Res.

151

161

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[1] We present new observational data on small-angle light scattering properties of natural, random shaped particles, as contrasted with spherical particles. The interest in this ''shape effect'' on scattering arises from the need for a suitable kernel matrix for use in the laser diffraction method (LD) of particle sizing. LD is now used broadly for measuring size distribution of suspended marine particles. LD involves the measurement of small-angle forward scattering at multiple angles. This data is inverted using the kernel matrix to produce size distribution. In the absence of a suitable matrix for random shaped particles, past practice has been to use a model based on Mie theory, applicable strictly only to homogeneous spheres. The present work replaces Mie theory with empirical data. The work was motivated in part by anomalous field observations of size distribution and settling velocity distributions reported in literature. We show that a kernel matrix for random shaped particles results in improved interpretation of field multiangle scattering observations. In particular, a rising edge at the fine particle end of the size spectrum is shown to be associated with shape effects.

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“…To illustrate the latter, in LD small irregularities on the surface of the particles are known to give rise to high angle scattering, which is interpreted by some laser diffractometers as small 'ghost' particles. Second, since the measured scatter intensities will be processed by the LD instrument on the basis of an assumed sphericity of the particles, all shapes that significantly differ from spherical may give rise to seriously biased results [21,22]. Finally and third, the scattered light is generally assumed to be averaged over the various orientations of the particles relative to the laser beam [23].…”

Section: Introductionmentioning

confidence: 99%

Particle shape and orientation in laser diffraction and static image analysis size distribution analysis of micrometer sized rectangular particles

Tinke¹,

Carnicer

Govoreanu³

et al. 2008

Powder Technology

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A systematic study has been described on the laser diffraction (LD) and static image analysis (SIA) of rectangular particles [1]. To rule out powder sampling, sample dispersion and particle orientation as a possible root cause for differences in size distribution profile, powder samples were initially immobilized by means of a dry disperser onto a glass plate. For a defined region of the glass plate the diffraction pattern as induced by the dispersed particles, and the 2D dimensions of the individual particles were measured by LD and optical microscopy, respectively. Correlation between LD and SIA could be demonstrated considering the scattering intensity of the individual particles as the most dominating factor. For both spherical and rectangular particles, theory explains the latter to relate to the square of their projected area. In traditional LD, the size distribution profile is dominated by the maximum projected area of the particles (A), and the diffraction diameters of a rectangular particle with length L and breadth B are perceived by the LD instrument to correspond by approximation with spheres having a diameter of ∅ L and ∅ B , respectively. Weighting for differences in scattering intensity between spherical and Page 3 of 56 rectangular particles exlains each rectangular particle to contribute to the overall LD volume probability distribution proportional to A 2 /L and A 2 /B. Accordingly, for rectangular particles this scattering intensity weighted diffraction diameter (SIWDD) concept explains an overestimation of their shortest dimension and an underestimation of their longest dimension. For this study various samples have been analysed with the longest dimension of the particles ranging from ca. 10 to 1000 µm. For a variety of pharmaceutical powders all with a different rectangular particle size and shape, the demonstrated correlation between LD and SIA aims to facilitate the user in a better validation of LD methods based on SIA data.

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Correction of the Effect of Particle Shape on the size distribution measured with a laser diffraction instrument

Cited by 28 publications

References 5 publications

Particle engineering: A strategy for establishing drug substance physical property specifications during small molecule development

Particle engineering: A strategy for establishing drug substance physical property specifications during small molecule development

Light scattering by random shaped particles and consequences on measuring suspended sediments by laser diffraction

Particle shape and orientation in laser diffraction and static image analysis size distribution analysis of micrometer sized rectangular particles

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