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BI-DCP – Disc Centrifuge Photosedimentometer

  • BI-DCP Particle Size Analyzer

Differential Centrifugal Sedimentation (DCS)

High-Resolution Particle Size Analysis

The Brookhaven BI-DCP Disc Centrifuge Photosedimentometer (DCP) is a digitally controlled, high-resolution, particle size distribution analyzer. It yields high-resolution results in the size range from 0.01 to 30 microns with typical analysis times ranging from 5 to 30 minutes. The BI-DCP software provides easy instrument control, data analysis, and database management. The software is menu-driven and permits a variety of report formats.

Brookhaven Instruments is renowned for light scattering instruments dedicated to sub-micron particle sizing and polymer characterization. Having identified the need to produce high resolution in the 1-micron size range, Brookhaven has produced an instrument with a resolution unmatched by any other technique in this range. Sedimentation is intrinsically a fractionation technique and the BI-DCP Particle Size Analyzer provides a means to separate the components of mixtures and also characterize a wide variety of distributions.

Differential Centrifugal Sedimentation Particle Size Analysis

Try our DCP Modeling Utility: Quickly model your measurable particle size range before running DCP experiments—just input sample and spin parameters to eliminate guesswork and save time. Available as a free standalone download. 

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Overview

Features at a glance

  • Resolves particle sizes in complex mixtures
  • Simple, rapid operation, stable
  • No calibration necessary, exact derivations
  • Suitable for a wide range of sizes and densities
  • Variety of operating modes
  • External and internal gradient
  • LINE or HOST start methods
  • Successive sample injections allowed
  • Stationary or scanning detector
  • variable rotation speed
  • Quantitative determination of weight distributions
  • Optimize experimental conditions in advance
  • Customizable analysis and reports
  • Continuous monitoring of temperature

 

No other type of instrument can resolve several peaks in the difficult range of around 1 micron.

The DCP incorporates a custom electronic drive system with high efficiency while operating quietly on your benchtop. An integral strobe light is synchronized to the drive circuit to check the hydrodynamic stability of the sample. A sensor is used to monitor the temperature in the disk. The BI-DCP offers the largest range of speeds, 500 to 15,000 rpm, which allows an even greater range of particle size measurements. A scanning detector head reduces measurement time.

 

Benefits of Use

An instrument is an investment in the present as well as in the future. The BI-DCP is truly cost-effective because it enables users to:

  • Resolve complex particle size distributions to improve rheological and structural properties.
  • Monitor incoming raw materials to reduce rework.
  • Fingerprint finished products to minimize lot-to-lot variations.
  • Increase cost-effectiveness by reducing process and scale-up time.
  • Optimize material properties to enhance product performance.
  • Study particle size fundamentals to develop new products and processes.

Measurement Principles

Measurement Principles

Particles scatter and for some, absorb light. A beam of LED light is used, and the following relationships describe the basic principles of the DCP. This analysis relies on a simplified form of light scattering, namely turbidity. Whereas static and dynamic light scattering rely on the quantification of scattered light to calculate particle size, turbidity only requires that you be able to measure the light lost due to scattering and/or absorption, essentially via a reduction in transmittance.

 

  • It =  I0 exp (-Qext * C * L)  where I0 = incident intensity and It  is transmitted intensity
  • Qext = Extinction efficiency = f(dp, np/nf, λ)
  • c = Mass concentration
  • L = Path length (width of the fluid segment in the disc)
  • Light is either absorbed or scattered, the sum of which is called extinction.
  • Extinction is a strong function of particle size. Significant optical corrections are necessary for dp ≤ 5 μm
  • Sensitive, but less quantitative for high-density materials such as metal oxides where Qext is not easy to calculate accurately.

 

The key equation for the diameter of the particle is:

image of particle diameter equation

 

Note that the relationship between time and particle size squared is inversely proportional.

Where:

t = time

ƞL = viscosity of the liquid

RD = radius of the detector

RI = radius to the meniscus

ρp = density of the particle

ρL = density of the liquid

disc centrifuge x-ray sedimentometry illustration

 

The final particle size distribution obtained from the BI-DCP depends on hydrodynamics to the extent that this dictates the time required for a band of particles to pass the detector.  The optical correction becomes more difficult when materials with complex refractive indices are considered, such as metal and metal oxide particles.  These sorts of samples are better suited to X-ray detection.  Higher atomic mass nanomaterials tend to have higher densities, and thus sediment more rapidly. This is common with metal and metal oxide particles.

Typical Applications

Applications 

The versatile BI-DCP offers high resolution results to particle sizing problems where the particles are dispersed in a liquid and cover the size range from 0.01 to 30 microns. This range is useful for a variety of materials and many applications:

  • Polystyrene, PVC, other polymers
  • Carbon blacks
  • Metal oxides, refractories
  • Ink particulates, alumina, titania
  • Pharmaceuticals, cosmetics, foods
  • Coatings, paints
  • Minerals, silicas
  • Clays, ceramics

 

A Case History:

The Bl-DCP’s value was demonstrated in a coatings application involving an emulsion polymerized latex. The performance of the coating varied from batch-to-batch with each latex produced, and was not within he desired specifications. So, the unacceptable product was discarded or stored for use in less exacting applications. This resulted in increased handling charges, storage/disposal problems and greatly reduced profitability. Using the Bl-DCP, the problem was traced to variations in the particle size distribution of the latex produced in a typical large production reactor. The detection of variations in particle size distributions and the subsequent corrections, resulted in much tighter controls over the end product. This in turn resulted in a completely usable product that eliminated storage/disposal problems and brought the company higher profit margins.

Specifications

Specifications 

AnalysisSize range of 0.01 to 30 µm maximum; 0.05 to 10 µm typical for low density particles, 0.01 to 2 µm for high density particles; wide variety of materials dispersed in water and other solvents
Data SystemWindows computer with printer. Real time graphics and data display, high resolution color (SVGA). Menu driven data analysis and management system, with single copy license and software distribution copy.
Drive SystemMicroprocessor controlled digitally driven electronic motor. Digital readout for setting and monitoring speed. Speed continuously variable from 500 to 15,000 rpm. Speed accuracy and stability better than + 0.01%. Temperature sensor and digital readout. Dual purpose integral strobe.
Disc CavityPolymethylmethacrylate with stainless steel hub. Dynamically balanced over range of rotational speeds. Spin fluid volume from 10 to 40 ml.
Power Requirements100/115 VAC, 220/240 VAC, 50/60 Hz, 1,000 Watts
Dimensions260 x 500 x 550 mm (HWD)
Weight33 kg
CertificationsCE Marked

A policy of continual improvement may lead to specification changes

Options & Accessories

Accessories

Standards

BI-SVK993 Particle size validation kit, (993 +/- 21) nm
BI-LTX993Latex reference material, nominal 993 nm
BI-TIO2Titanium dioxide reference material, MMD ~ 300nm
Syringe KitIncludes Syringes, tubing, etc.

Replacement Parts

BI-DSCStandard disc for aqueous dispersions, 15,000 RPM max, PMMA
BI-DSCRDisc for use with aggressive solvents, 10,000 rpm max, polycarbonate

Download Brochure

Available Downloads 

BI-DCP Brochure PDF

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