Abstract
Theoretical sphericity factors for objects of various geometric shapes were calculated based on ideal performance of a light blockage detector, an electrolyte displacement sensor, and an automatic image analyzer performing microscope oversize counts based on the horizontal projection of the objects. The sphericities calculated relate the dimension of these objects to the measurement required by the USP method, i.e., the longest effective linear dimension. Using as a mathematical model a suspension which at the 10-?m size contains five spheres, five cubes, 15 equants, five rods, 10 prolate ellipsoids, five flakes, and five fibers per milliliter, it is shown that while the hypothetical suspension would barely meet the USP requirement for large-volume parenterals, based on the longest dimension by manual microscopy, only about one-third of these particles would be detected using electrolyte displacement, about one-half would be accounted for by light blockage, and on the average the automated microscope would reveal almost three-fourths of the particles present. The use of correction factors to account for these discrepancies is suggested.
- Received December 14, 1979.
- Accepted February 20, 1980.
- Copyright © Parenteral Drug Association. All rights reserved.
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