Particles of uniform spheres and diameter have long been used as size references to estimate the sizes of other particulates, biomolecules, and living organisms.  They can also be utilized to conduct routine calibration and checking of the performance of particle sizing instruments.  In addition, QC and validation of analytical methods often depend on them to meet various requirements and regulations.  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.
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.
Nano-Micro supplies a full range of size standard microspheres based on patented particle technology.  All of them 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 by Nano-Micro are either cross-linked polymer or silica microspheres.  The polymer particle size standards above one micron in diameter are based on highly crosslinked polystyrene or poly(methyl methacrylate) for improved physical and chemical stability.  Nanomicro Tech particle size standards are dispersed in water of high purity and some of them contain a small amount of surfactant to ensure a good dispersion.  Packaged in 10 or 15 mL dropper-tipped vials at the solids content of 1 wt%, these aqueous dispersions of the particle size standards are easy to store and dispense.  Dry powder samples of the particle size standards are also available upon request.

Product Characteristics:
Broad size range available from nano to micron-scale
Diverse material selection from different polymers and silica
Perfect roundness
Sharp particle size distribution
Stable physical and chemical properties
Nano-Micro. Size Standards.Submicron Particles on CPS Disk Centrifuge (Left) and Micron-sized particles on Beckman Coulter Multisizer III (Right)

Nanomicro Tech. Size Standards Specification

Nano Particle Size Standards

Micron Particle Size Standards