Calibration standards (NIST)
This range of Estapor© Calibrated Standards Microspheres is used in scientific and industrial laboratories for the calibration and the standardization of particle measurement systems. They also can be used in quality control programs and development of new analytical methods in numerous fields.

Principle of measurement:
First ECS sample and Standard Reference Material 1690 or 1691 (NNBS) are mixed together. Then, this preparation observed by Transmision Election Microscope (TEM) and photo are taken.

Our Calibration Standard Microspheres are supplied at 0.5% concentration in water (50mg/10ml).

Functionalized Estapor® Microspheres
Our functionalized polystyrene microspheres are extremely uniform with an excellent lot-to-lot reproducibility. The introduction of highly polar or ionisable chemical groups increases the colloidal stability of the suspension and also allows the covalent binding of polyclonal or monoclonal antibodies, proteins and haptens.

The different groups -COOH, -NH 2 , -OH, -CONH 2 , -SO 3 H, -COOCH 3 are produced by copolymerisation of the corresponding functional monomers. Due to their more hydrophilic surface, our functionalized polymer microspheres have a very low grade of non-specific-binding.

The most popular protocols for covalent binding have been carried out with our functionalized Microspheres (see our Estapor® Technical Data Sheets "ETDS", page 15 - Annexe).

We offer a large range of sizes (from 50 nm to 2 µm and more), making this range suitable for most microspheres-based technologies.

Our Estapor® Microspheres are worldwide used for the following applications:
• Immunoturbidimetric and Nephelemetric Assays
• Enhanced Immunoturbidimetric Assays
• Latex Agglutination Test "LAT"
• Solid phase ImmunoAssays
• Microspheres capture ELISA

Our Estapor® Microspheres are currently made by emulsion polymerization using different type of surfactants which usually are negatively charged.
Once adsorbed onto the surface of the microspheres, those surfactants induce an increased colloidal stability.

On the other hand, surfactants are well known for interfering with the binding or coupling of proteins onto the microspheres.
Then, it is recommended to remove all surfactant, by additional washing steps. Most of the microspheres developers and users know how tedious washing steps are with small microspheres. For an efficient washing procedure, small microspheres need to be first centrifuged at a high speed and then they must be completely redispersed in an appropriate buffer.

Recently, our chemists working at the Estapor® Technical Center, have come over with new Surfactant Free products.

Most of the Microspheres developers know how tedious washing steps are with small polystyrene microspheres (low sedimentation behaviour even when centrifuged at high speed).
Microspheres greater in density than 1.06 (for polystyrene) are more easily spun down.

Hydrophilic microspheres such as COOH-modified ones are less likely to clump irreversibly during the centrifugation washing process.

With a high density (1.2g/cm3) and a very high concentration up of COOH groups (>400 µEq/g), our chemists have come with new High Density COOH-Microspheres.

Standard Plain Polystyrene Microspheres

Large Plain Polystyrene Microspheres

Estapor® Calibrated Standards Microspheres

Very small Carboxyl-Modified Microspheres (-COOH)
Density : 1.059 g/cm3

Standard Carboxyl-Modified Microspheres (-COOH)

Large Carboxyl-Modified Microspheres (-COOH)

Very Small Amino-Modified Microspheres (-NH 2 )

Amino-Modified Microspheres (R-NH 2 )

Standard Amino-Modified Microspheres (Ar-NH 2 )

Hydroxyl-Modified Microspheres (-OH)

Sulfite-Modified Microspheres (-SO 3 H)

Quaternary Ammonium-Modified Microspheres [(-CH 3 ) 3 N+)]

Chloromethyl-Modified Microspheres (-CH 2 Cl)

Sulfate-Modified Microspheres (-SO 4 H)

Carboxyl-Modified Microspheres (-COOH)

Amide-Modified Microspheres (-CONH 2 )

Surfactant-Free Polystyrene Microspheres.
Density: 1.059 g/cm3

High density COOH-Polystyrene Microspheres
Density: 1.2g/cm3