PTL News

The Journal of GXP Compliance - [Spring 2011] issue features an article by PTL's Analyst, Rebecca Wolfrom.  Entitled The Language of Particle Size, this article addresses the importance in understanding how distributions and associated statistical terms relate to particle size analysis and subsequent compliance to specifications.  To learn more about the Journal of GXP Compliance and this article, visit www.gxpandjvt.com.

The Language of Particle Size

Rebecca Wolfrom, Fine Particle Analyst I

ABSTRACT

The vocabulary of particle size analysis is unique and complex.  Each sizing technology uses its own “language” for data expression and graphical representation.  Clear understanding of the varying terminology is necessary for correct interpretation of the data.   With this knowledge and understanding, a material’s compliance to established specifications can then be determined.  This article will enable the reader to understand current particle size terminology and definitions, associated assumptions with different technologies, as well as the fundamental differences in graphical representations by histograms or cumulative distributions.

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The Journal of Validation Technology - [Winter 2011] issue features an article by PTL's Senior Chemist, Eric Olson.  Entitled Blending of Log Normal Particle Size Distribution Data from Multiple Image Analyses into a Single Continuous Data Set, this article addresses how to blend multiple image analyses in a useful continuous particle size distribution with optimal accuracy.  To learn more about Journal of Validation Technology and this article, visit www.gxpandjvt.com.

Blending of Log Normal Particle Size Distribution Data from Multiple Image Analyses into a Single continuous Data Set

Eric Olson, Senior Chemist

ABSTRACT

Image analysis is one method by which particle size may be measured.  In many cases, it is considered the “gold standard” of particle size measurement and is often used to verify the results of other techniques.  Sample particle size distributions are often broad, sometimes covering two to three decades of particle diameter.  It is also common to analyze samples that are multi-modal, e.g., a single sample that may contain primary particles and hard agglomerates with overlapping particle size distributions.  Typical results when analyzing these samples are frequently inaccurate at the particle size extremes, depending on the instrument operating parameters used.  This paper describes a methodology by which data from multiple image analyses that used different operational parameters are exported from the instrument into a suitable spreadsheet.  The data are then be blended into a useful continuous particle size distribution with optimal accuracy.

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PTL is pleased to announce that Bill Kopesky, Vice President of Analytical Services has been named to the Editorial Advisory Board for both The Journal of Validation Technology and The Journal of GXP Compliance. 

Effective January 1, 2011, Bill will contribute his expertise in particle size characterization to two respected industry journals.   The Journal of Validation Technology is a peer-reviewed publication that provides an objective forum for the dissemination of information to professionals in regulated industries. The Journal of GXP Compliance embraces a comprehensive approach that includes information in advance of compliance performance, demonstrating compliance, and maintaining a compliant state.  For both journals, members of Editorial Advisory Board review article submissions to ensure that they have been researched thoroughly, reflect current industry standards, and are not promotional in nature. 

We look forward to the industry benefiting from Bill's many years of expertise in particle characterization and compliance! See the combined website for these scientific journals here.

The Model 95 Fisher Sub-Sieve Sizer is an odd sight in PTL's collection of state of the art, computerized particle testing equipment.  Built on a particle testing technique dating at least to the 1940s, the instrument's wood housing, rubber tubing and analog manometer for fluid pressure measurement may inspire more nostalgia than technical confidence at first glance.

But lately, it seems the pharmaceutical industry can't get enough of this classic particle testing technique.  PTL clients are increasingly requesting testing via FSSS per current ASTM, ISO and USP methods. The Sub-Sieve Sizer tests powders quickly and reproducibly for their Average Particle Diameter - also known as the Air Permeability Diameter.   

The analytical technique determines the average particle size by measuring the pressure drop across a packed powder bed using a water manometer.  The pressure drop is a function of the permeability of the packed bed.  This is related to the surface area of the particles which is then transformed to an "average size" based upon the assumption that the particles are spherical.  The disadvantage of the technique is that it does not report on the statistics of the size distribution.