FOQELS

Fiber Optic Quasi Elastic Light Scattering
Particle Sizing in Concentrates by Dynamic Light Scattering

A special Instrument

At last, a simple, practical approach to automatic particle size analysis of concentrated suspensions. Brookhaven Instruments brings together the fiber-optic (FO) detection and quasi-elastic light-scattering (QELS) technologies to create the innovative FOQELS particle size analyzer. The Brookhaven FOQELS particle size analyzer allows measurements to be made over a much greater range of concentrations than than standard Dynamic Light Scattering (DLS) instruments. The unique, state-of-the-art, optical microfiber probe (US Pat. No. 5,155,549) provides the key technology for a compact and inexpensive instrument to measure in suspensions concentrated up to 40% by weight. Our new high-temperature sample cell holder provides controlled temperatures from ambient up to 160 C. This device uses a space-age insulation material and is ideal for applications such as high-temperature oils.

FOQELS shown with the high temperature sample cell holder

Operation

Two fibers are housed in a single stainless steel probe. In use the probe is positioned to view the sample either through the wall of a cuvette or through a window. The illustration below shows details of the construction of the probe. Note that the probe does not touch the cuvette wall and that the sample never touches the probe.

Principle of Operation: Visible light from a laser diode is launched into the sample via a monomode fiber and the scattered light is collected by a second monomode fiber at an angle of 153 . The scattered light is analyzed using the established techniques of Dynamic Light Scattering (DLS) with our TurboCorr digital autocorrelator. The troublesome homodyne signals that arise in single fiber optic designs are eliminated. The FOQELS yields accurate and reliable results because it operates in a well controlled self beating mode.

Typical Applications

• Particle sizing in situ!, and in real time!
• Micro-emulsion technology
• Stratification and hydrodynamic instabilities
• New!! High temperature capability for oils and similar
• Emulsion polymerization, particle size growth
• Metallic oxide manufacture
• Nucleation processes
• Medical and biological systems
• Protein crystal growth
• Cataractogenesis in human eye lenses

Specifications

Suspension Concentration: 0.001% to 40% (approx.) Actual range of applicability depends on both particle size and concentration.

Size Range: 0.002 to 2 microns

Sample Type: Most colloidal sized materials suspended in any liquid.

Temperature Control: 4 C to 70 C. or ambient to 160 C using the high temperature cell holder option (see below.)

Dimensions:
Probe length: 1 meter standard (other lengths available)
Probe termination: 85 mm long, 6mm diameter, stainless steel
Control Unit: 85(H) x 210(W) x 230(D), mm

Weight: 2 Kgs

Power Requirements: 100/115/220/240 VAC 50/60 Hz, 200 Watts.

Computing: Requires link to a Windows PC which carries a TurboCorr digital autocorrelator. Such computers can be supplied by BIC with the instrument.

A policy of continued improvement may lead to specification changes

Options and Accessories

BI-FHTC: This high-temperature sample cell holder provides controlled temperatures from ambient up to 160 C. It uses a space-age insulation material and is ideal for applications such as high-temperature oils.