NIST Traceable Particle Size Standards


1. Size standard particles have long been used as size references to estimate the sizes of other particulates, biomolecules, and living organisms.

2. Particle size standards can also be utilized to conduct routine instrument calibration,development and testing of particle sizers, particle counters

3. Instrument QC: check for instrument problems and shifts in laser function, check the calibration curve shape, etc.

4. Equipment efficiency studies: vial cleaning, contamination studies, filter testing (including filter leaks), broad distribution material analysis.

5. Spacers: liquid crystal displays, precision microelectronics

To serve as a size reference, the particle size and size distribution of the monodisperse microspheres are determined by established standard methods.

These well characterized size standards have become valuable in applications including microscopy, physical measurement of micron and submicron sizes, study of colloid systems and equipment efficiency.

Size Standards History

Particle size standards are typically either crosslinked polymer or silica microspheres. Traditional particle size standards made of non-crosslinked polystyrene are only stable in aqueous dispersion and form aggregates upon drying. Crosslinked particles have much higher physical and chemical stability than non-crosslinked particles and can be stored as dry powder or aqueous dispersion.

Silica microspheres are designed for applications requiring additional rigidity and durability especially in organic solvents. The density of silica particles is much higher than that of the polymer particles. Under optical and electron microscopes, more contrast appears from the opaque silica particles than the polymer particles.

What Can We Supply?

EPRUI Biotech supplies a full range of size standard microspheres based on patented particle technology. All of our standard particles are determined by Coulter Counter, DPS Disk Centrifuge, Dynamic Light Scattering, TEM, SEM, and Optical Microscope against Standard Reference Materials (SRMs) from the National Institute of Standards and Technology, U.S. Department of Commerce (NIST). The particle sizes of these microspheres are therefore traceable to globally recognized primary standards of NIST SRMs.

All particle size standards supplied from EPRUI are either cross-linked polymer or silica microspheres. The polymer particle size standards >1um in diameter are based on highly crosslinked polystyrene or poly(methyl methacrylate) for improved physical and chemical stability.


EPRUI supplies particle size standards dispersing in ultrapurewater and some might contain a small percentage of surfactant to ensure a good dispersion.

Packing in 10ml dropper-tipped vials with w/v 1%. These aqueous dispersions of the particle size standards are easy to store and disperse. Dry powder samples of the particle size standards are also available upon request.