Dynamic Light Scattering Particle Size Analyzer

What is the Dynamic Light Scattering Particle Size Analyzer?

A dynamic light scattering analyzer that determines hydrodynamic diameter of sub-micron particles and macromolecules from Brownian-motion fluctuations. It fits dilute colloids, proteins, liposomes and emulsions in the roughly 1 nm to 10 µm range where laser diffraction loses resolution.

Overview

A dynamic light scattering analyzer illuminates a dilute suspension with a coherent laser, usually 633 nm, and records scattered intensity at 90°, 173° backscatter or both using an avalanche photodiode. A digital correlator builds the autocorrelation function, and cumulant or regularisation algorithms derive the diffusion coefficient, which the Stokes–Einstein equation converts to a z-average hydrodynamic diameter and polydispersity index. Temperature control of the cuvette holder, typically 0 to 90 °C, is essential because viscosity and diffusion depend on it. Backscatter detection tolerates higher concentrations and reduces dust sensitivity. Results are intensity-weighted, so a few large aggregates can dominate; volume and number conversions are model-dependent. Sample volumes can be as low as 2 to 12 µL in microcuvettes, which suits scarce biologics.

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?

• Hardware correlator with cumulant and multi-exponential analysis
• Backscatter 173° detection for concentrated and turbid samples
• Peltier temperature control of cuvette holder from 0 to 90 °C
• Microcuvette option requiring only a few microlitres of sample
• Polydispersity index and size quality indicators in the report
• Optional zeta potential and titration accessories

What are the technical specifications?

A typical dynamic light scattering particle size analyzer configuration offers size range of 0.3 nm–10 µm, measurement principle of Dynamic light scattering (photon correlation), laser of He-Ne 633 nm or 532 nm solid state, detection angle of 90° and 173° backscatter, temperature range of 0–90 °C, ±0.1 °C and minimum sample volume of ≥ 2 µL (microcuvette). 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 Dynamic Light Scattering Particle Size Analyzer is used in protein aggregation screening, liposome and lipid nanoparticle sizing, latex and polymer dispersions, nanoemulsion stability studies and quantum dot and metal colloid characterisation. 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 Dynamic Light Scattering Particle Size Analyzer?

Choose dynamic light scattering when the sample is a dilute, stable suspension below about 1 µm, when sample volume is limited, or when you need hydrodynamic size and polydispersity. Specify the concentration range, temperature control, cuvette type, need for zeta potential or titration, and any 21 CFR Part 11 requirement. For broad distributions extending into tens of micrometres, laser diffraction is more appropriate.

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.