Electrozone sensing

The electrozone sensing technique, also called the Coulter principle, was originally developed for biomedical applications for counting blood cells. This method counts and sizes particle based on changes in the electrical resistance caused by nonconductive particles suspended in an electrolyte. It presently finds uses in a wide variety of industries, including the food, environmental, coatings, ceramics, and metals industries. 

Larry Arnold, a technician with the National Soil Survey Laboratory in Lincoln, Nebraska, prepares soil samples for particle size analysis. 

Drawing a partial vacuum on the sensing cell carefully controls the quantity of the suspension drawn through the aperture. This allows for repeatable measurements. 

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Several methods are used to determine the size of particles. They include sieves, sedimentation, electrozone sensing, microscopy, and light scattering. The method selected will depend on the application. 

Figure 15.26 shows a schematic of an electrozone sensing cell. The suspended particles are placed in a container with two electrodes. One of the electrodes is within a tube that has a small hole, or aperture, in it. If there is no obstruction in the orifice, a steady current flows between the electrodes. As the particle moves near the sensing zone, it displaces a volume of the conductive electrolyte equal to the volume of... 

Electrophoresis, see Polyacrylamide gel electrophoresis Electrozone sensing, 583 Ellipticity, CD spectra, 196, 221,... 

Malvern Sysmex SD-2000 particle counter and sizer delivers high-performance particle size analysis from 1 to 120 pm by combining electrozone sensing with hydrodynamic sheath flow focusing. 

Multiple techniques can be used to measure the particle size distribution, for example electrozone sensing, sedimentation, laser diffraction, and microscopy. With the exception of microscopy, they all require calibration and the results depend on the technique. For example, in a round-robin study reported in Reference 4, the commonly used electrical sensing zone technique (Coulter Counter) was compared to microscopy and sedimentation. The average particle size determined by the electrical sensing zone method was by about 25%... 

In the electrozone sensing method of size analysis, (a) what equivalent sphere particle diameter is measured and (b) what type of distribution is reported ... 

The cellulosic fibers in the samples were counted by using instruments based on the electrozone sensing technique. For... 

Some popular methods of particle size analysis and their ranges of applicability are listed in Table 8.3. The methods used most often to analyze polymer emulsions, described below, are conveniently divided into three categories (a) ensemble techniques (e.g. laser diffraction (LD) and dynamic fight scattering (DLS)) (b) separation techniques (e.g. capillary hydrodynamic fractionation (CHDF) and disk centrifugation) (c) ultrahigh separation techniques (e.g. SPOS and electrozone sensing). 

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