Centrifugal Sedimentation Particle Size Analyzer

What is the Centrifugal Sedimentation Particle Size Analyzer?

A sedimentation analyzer that applies Stokes' law under centrifugal force, detecting particles by light or X-ray attenuation as they settle. It provides high-resolution separation of narrow and multimodal distributions from about 10 nm to 100 µm, particularly for latex, pigments and fine ceramics.

Overview

In a disc or cuvette centrifuge, particles settle through a fluid of known density and viscosity at a controlled speed, typically up to 24000 rpm for disc types, and detectors measure turbidity or X-ray absorbance versus time or radius. Stokes' law gives diameter from settling velocity, and because separation occurs physically before detection, the method resolves closely spaced peaks such as 220 and 240 nm latex that light-scattering methods merge. A density gradient in the disc stabilises the sample zone. Particle density must be known, and shape effects and fluid effects must be controlled. Analysis takes several minutes to an hour, slower than diffraction, but the resolution benefits formulation and nanoparticle development where multimodal populations carry functional significance.

How does it work?

Laser diffraction analyzers pass a laser beam through a dispersed sample; particles scatter light at angles inversely related to their size, and a detector array records the angular intensity pattern. The Mie or Fraunhofer model converts this pattern into a volume-based size distribution. Dynamic light scattering instead measures intensity fluctuations caused by Brownian motion, and the Stokes–Einstein equation converts the diffusion coefficient into a hydrodynamic diameter. Dynamic image analysis captures particle silhouettes with a high-speed camera and reports size and shape descriptors directly. Sedimentation methods apply Stokes' law to settling velocity under gravity or centrifugal force. Key components include the light source, sample dispersion unit (wet or dry), detector array or correlator, and software with optical-property databases.

What are the key features?

• Disc or cuvette centrifuge with speed to 24000 rpm
• Physical separation before detection for high peak resolution
• Optical turbidity or X-ray absorbance detection options
• Density gradient fluid preparation for stable sample zone
• Automatic calibration with internal standard
• Programmable speed ramps for wide distributions

What are the technical specifications?

A typical centrifugal sedimentation particle size analyzer configuration offers size range of 10 nm–100 µm (density dependent), measurement principle of Centrifugal sedimentation, Stokes' law, maximum speed of 24000 rpm (disc), detection of Optical turbidity or X-ray absorbance, sample volume of ≈ 0.1 mL per injection and resolution of Separates peaks with ≤ 5% size difference. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Centrifugal Sedimentation Particle Size Analyzer is used in latex and polymer emulsion characterisation, nanoparticle formulation development, pigments and carbon black, fine ceramic powders and silica and catalyst supports. Across the wider Particle Size Analyzers class, laboratories also deploy it for pharmaceutical powder and inhaler development, battery cathode and anode materials and ceramics and cement.

Which standards and certifications apply?

Relevant standards and methods include ISO 13320, USP <429>, ISO 13322-1, ISO 13322-2, ISO 22412, GB/T 19077 and Ph. Eur. 2.9.31. Certification candidates for this model are CE and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Particle size results depend heavily on sampling and dispersion, so representative sub-sampling, a documented dispersion protocol and sonication or pressure settings must be validated for each material. Install the instrument on a vibration-free bench away from direct sunlight, and keep the optical bench clean; check background and alignment before each session. Verify performance periodically with certified reference materials such as polystyrene latex or glass beads, following ISO 13320 acceptance criteria. Replace dispersant and clean the cell to avoid carry-over. Enter refractive index and absorption values correctly, because they strongly influence Mie results. Regulated laboratories should perform IQ/OQ/PQ and use audit-trail-enabled software.

How do I select the right Centrifugal Sedimentation Particle Size Analyzer?

Select centrifugal sedimentation when resolving multimodal or very narrow distributions of fine particles matters more than speed, and particle density is known. Specify size range, particle and fluid density data, detector type (optical or X-ray), injection volume and speed range. Broad routine QC of powders is faster on laser diffraction, and unknown-density samples need extra characterisation.

How does it compare with other Particle Size Analyzers variants?

Start from the expected size range and sample state. Laser diffraction covers roughly 0.1 to 3500 µm and suits most powders and suspensions; dynamic light scattering is preferred below about 1 µm; dynamic image analysis is chosen when shape matters or when a few oversize particles must be detected; centrifugal sedimentation resolves narrow multimodal distributions of fine particles. Next decide between wet and dry dispersion: dry dispersion avoids solvents and suits free-flowing powders, while wet dispersion gives better deagglomeration of cohesive or fine materials. Check whether the method must follow ISO 13320 or USP <429>, and whether 21 CFR Part 11 audit trails are needed. Also consider sample volume, automation, cleaning time between samples and the availability of validated SOP templates.