Coulter principle

Cough medicines Coulomb s law Coulometry Coulter principle Coumachlor [81-82-3]... 

The aperture impedance principle of blood cell counting and sizing, also called the Coulter principle (5), exploits the high electrical resistivity of blood cell membranes. Red blood cells, white blood cells, and blood platelets can all be counted. In the aperture impedance method, blood cells are first diluted and suspended ia an electrolytic medium, then drawn through a narrow orifice (aperture) separating two electrodes (Fig. 1). In the simplest form of the method, a d-c current flows between the electrodes, which are held at different electrical potentials. The resistive cells reduce the current as the cells pass through the aperture, and the current drop is sensed as a change in the aperture resistance. 

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. 

Lines, R.W. 1996. The electrical sensing zone method (The Coulter Principle). In Liquid and Surface Borne Particle Measurement Handbook. (J.Z. Knapp, ed.) pp. 113-154 Marcel Dekker, New York. 

Dilute suspensions may be studied using the Coulter principle. It is sometimes found that the count level at the lower sizes decreases with time and this may be attributed to flocculation or dissolution. A problem arises in that the suspending liquid needs to be electrically conducting and one would expect this to reduce the potential energy barrier and decrease suspension stability [108]. 

The most widely used stream scanning technique employs the Coulter principle (Figure 9.1a) where the interrogating field is electrical and particle size (volume) is proportional to the change in electrical impedance as the particles pass through the field. 

The electrical sensing zone method (the Coulter principle)... 

The Coulter principle was patented in 1949 [2] and described in 1956 [3] as a method for counting and sizing blood cells. Kubitschek [4,5] introduced modifications which permitted the counting of bacterial cells, and pointed out that the method could be applied to the measurement of cell volumes as well as number counting. Modified instruments were soon developed with which particles could be sized as well as counted. In 1998 the company was acquired by Beckman and renamed Beckman Coulter. 

The Coulter principle is also standard for dry toners [8,9] and an accepted method for aluminum oxide powder [10], chromatography media [11], polymeric powders [12], plutonium [13], filter evaluation [14], catalytic material [15] and comparing particle size distribution using alternative types of particle counters [16]. In ASTM method C-21 it states that the experience of several laboratories indicates that the method is capable of a repeatability of 1% and a reproducibility of 3% at the 95% confidence level. Operating procedures for this technique are also covered in BS3405 [17]. The method is also the subject of an international standard [18]. 

The Coulter principle has also been applied to fiber length determination [74,75] in which the aperture length was made greater than the fiber length. This approach is interesting in that the pulse duration is a measure of fiber length and pulse height is a measure of fiber volume. 

Drop size distribution in dilute suspensions of electrical conducting liquids may be determined using the Coulter principle but the need to add what may be undesirable conductive materials limits its applicability [213-215]. The use of chemical means to measure interfacial area has been used extensively for gas-liquid dispersions. Chemical reaction methods for determining the interfacial area of liquid-liquid systems involve a reaction of a relatively unchanging dispersed-phase concentration diffusing to the continuous phase. The disadvantage of this approach is that the mass transfer can affect the interfacial tension, and hence the interfacial area [216-218]. 

British Standard BS3405 Part 5,(1983), Determination of Particle Size Distributions, Recommendations for the Electrical Sensing Zone Method, The Coulter Principle, 450, 462, 463... 

Another clinical application of conductance is for electronic counting of blood cells in suspension. Termed the Coulter principle, it relies on the fact that the conductivity of blood cells is lower than that of a salt solution used as a suspension medium.The cell suspension is forced to flow through a tiny orifice. Two electrodes are placed on either side of the orifice, and a constant current is established between the electrodes. Each time a cell passes through the orifice, the resistance increases this causes a spike in the electrical potential difference between the electrodes. The pulses are then amplified and counted. 

A second class of measurement techniques, based on particle number, overcomes some of the problems associated with mass-based techniques. Electronic zone sensing, sometimes referred to as the Coulter principle, permits simultaneous particle size and number measurement. Particles are sized by suspending them in an electrolyte and drawing them through an aperture tube across... 

One of the earliest electronic particle sizing devices available was developed in the late-1940 s and was originally designed to count blood cells (Coulter, 1956). The Coulter Counter rapidly gained immense popularity in many industry and research applications, including the Earth sciences, and is still a very commonly used instrument in sedimento-logical laboratories. The Coulter Principle is sufficiently well established to be included in many A.S.T.M. (American Society for Testing Materials) reference method standards. 

Coulter, Wallace H. (1913-1998) was born in Little Rock, Arkansas. He patented the Coulter principle in 1953 and began production of the Coulter counter with his brother Joseph. The instrument was originally used to count blood cells. He established the Coulter Corporation in Miami Florida in 1961. 

Coulter counter Coulter principle Electrical particle detection... 

To date, nanofluidic single-molecule detection has been done in two ways. One takes the advantage of the comparable size of nanochannels and macromolecules and detects the modulation of ion current through a nanochannel or a nanopore when an individual macromolecule enters the nanochannel/nanopore. This method is well known as resistive-pulse sensing or the Coulter principle. The other uses a nanochannel as a confined region to limit the number of molecules inside the nanochannel and uses other methods such as optical microscopy to sense a single molecule inside the nanochannel. Both approaches have demonstrated successful detection of single molecules inside nanofluidic channels. However, to date, only a few examples for each approach have been reported since nanofluidic systems have been developed only within the last decade. 

Methods Based on Electrical Sensing Zone (or Coulter Principle)... 

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