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Fractionating Polymer Microspheres as Highly Accurate Density Standards.

Blox Bloxham^1,2, Jonathan W Hennek¹, Ashok A Kumar¹

¹†Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford St., Cambridge, Massachusetts 02138, United States.

Analytical Chemistry

|June 20, 2015

Summary

This study presents a new method for isolating small, accurate density-standard beads using aqueous multiphase systems (AMPS). This technique significantly narrows density distributions, improving bead accuracy for various scientific applications.

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Area of Science:

Materials Science
Analytical Chemistry
Physical Chemistry

Background:

Accurate density standards are crucial for applications like density gradient characterization.
Existing glass density standards are too large for many uses.
Commercial polymer microspheres have broad density distributions, limiting their precision.

Purpose of the Study:

To develop a method for isolating small, highly accurate density-standard beads.
To improve the precision of density standards for applications requiring fine density steps.
To reduce density heterogeneity in polymer microspheres.

Main Methods:

Fractionation of commercial polymer microspheres using aqueous multiphase systems (AMPS).
AMPS utilize polymer and salt mixtures that spontaneously separate into distinct density phases.
Characterization of bead densities using accurate and experimentally traceable techniques.

Main Results:

Successfully isolated microspheres with significantly narrower density distributions (standard deviations from 0.0003 to 0.0008 g cm(-3)).
Achieved a substantial reduction in density heterogeneity compared to original commercial microspheres.
Demonstrated improved accuracy for density standards by reducing bead density uncertainty.

Conclusions:

Aqueous multiphase systems (AMPS) provide an effective method for producing highly accurate, small density-standard beads.
This technique enhances the precision of polymer microspheres, making them suitable for demanding applications.
The method offers improved accuracy for density measurements by minimizing variability in standard bead densities.