BI-DCP

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

High Resolution Particle Size Analysis
The Brookhaven BI-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 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 resolution unmatched by any other technique in this range. Sedimention is intrinsically a fractionation technique and the BI-DCP provides a means to separate the components of mixtures and also characterize a wide variety of distributions.

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

The DCP incorporates a custom electronic drive system with high efficiency while operating quietly on your bench top. An integral strobe light is synchronized to the drive circuit for checking hydrodynamic stability of the sample. A sensor is used to monitor 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.

Data Analysis and Presentation

The BI-DCP Data System is a flexible and powerful tool that provides complete analysis and management of DCP data.Compatible with the newest PC, the DCP programs are menu-driven to provide both automatic data acquisition and database management for the Bl-DCP particle size analyzer and other disc centrifuges . The system's high resolution color display plots raw data in real time. Automatic and manual baseline selection, under the entire curve or peak-by-peak, and user-selectable extinction coefficient corrections are provided as are the uncorrected raw data. A color plotter provided with the system allows customized reports to be obtained
Reported results include.

• Number, Area, Weight average diameters and distribution widths.
• Polydispersity indices such as D w /D n and Std. Deviations.
• Overlays for comparison of distributions.
• Experimental conditions including run numbers, titles, and sample identifications.
• Raw data curve with base-line, differential and cumulative forms of the Number, Area, and Weight distributions.

A Database management facility includes: automatic data storage; menu-driven data retrieval (for review or reanalysis); and generation of tables of user-selectable results from the disk-based data for convenient comparison of runs.
The Bl-DCP Data System, including the interface hardware and cables, can be purchased separately for use with other disc centrifuges.

Operation Methods

Line Start Method (LIST)
While the disc is spinning, a small volume (typically 1/4 mL) of a dilute suspension (typically less than 1 % concentration) is injected onto the surface of a liquid (spin fluid) previously injected into the disc cavity. The particles sediment radially through the fluid in the centrifugal field. Spin fluid volumes are typically on the order of 15mL.

Light from a narrow-band, LED is passed through the disc. As particles pass through the light beam, the light intensity is reduced due to scattering and absorption. The transmitted light is measured by a photodiode and recorded by the computer as a function of time.

Hydrodynamically stable sedimentation is ensured by using any of the three gradient methods. A density and viscosity gradient between the suspension and spin fluid is created. The gradient cushions the hydrodynamic shock experienced by the particles as they enter the spin fluid. Thus a smooth transition and subsequent laminar flow is ensured.

The key to the very high resolution using the LIST method in the BI-DCP is the fractionation that takes place prior to detection. This is a result of starting all the particles sedimenting from the same position at the same time

Theory of Operation: Based on the principle of photosedimentation in a disc centrifuge, the BI-DCP utilizes the buffered line start, external gradient line start or homogeneous start methods of operation.The sedimentation behavior of particles depends on the particle density and the density and viscosity of the liquid through which the particles sedimentThe time, t, for a spherical particle of diameter, d, to travel from the initial radius, R j , at the surface of the spin fluid to the radius at the detector, R d . is given by:

This fundamental equation is easily derived by balancing the centrifugal, frictional drag, and buoyancy forces on the particle. Several interesting consequences arise.

The maximum size is primarily dependent upon the particle density and the fluid viscosity. For low density materials such as polymer latexes the maximum size is approximately 30 µm. For high density materials such as pigments or oxides the maximum size is about 5 µm.

These limits can be extended by decreasing the rate of sedimentation in several different ways: by selecting a more viscous spin fluid; by matching the particle and spin fluid density more closely; by using a lower rotation speedThe minimum size is limited by diffusion. For low density particles such as latexes, the minimum size is approximately 0.07 micron; for higher density particles such as carbon blacks, the minimum size is approximately 0.008 microns.

Homogeneous Start Method (HOST)
When stable sedimentation is not possible utilizing the LIST technique, the HOST technique is preferred. A larger volume (typically 10-20 mL) of the dilute suspension is injected directly into the disc cavity. Though resolution is lessened, a HOST run is simpler and, using the scanning mode, faster. Brookhaven can help you determine which technique will provide you with the best results.