Coulter method

The Coulter method of sizing and counting is based on measurable changes in electrical resistance produced by non-conductive particles suspended in an electrolyte. 

Because of this importance, different techniques have been developed to characterize the droplet size distribution in emulsions, each with its own pros and cons. Light microscopy, for example, is qualitative and only suited for particles larger than about 1 )im. When using electron microscopy, correct sample preparation is crucial to the examination and interpretation of the dispersions. The Coulter method is an indirect method which detects a... 

The overall initial particle size distribution used for the computations in this paper is on Figure 5. This thirteen-step distribution was the most recent of several taken by the Coulter Method (MeOH, LiCl) and is in agreement by shape and mean diameter to previous Coulter and other determinations (16,3A). This determination, as well as the percent sulfite in the solid is critical to calculating the initial number of particles in an experimental run ... 

FIGURE 27.1 Coulter method. Blood cells are surrounded by an insulating membrane, which makes them non-conductive. The resistance of electrolyte-filled channel will increase slightly as cells flow through it. This resistance variation yields both the total number of cells which flow through the channel and the volume of each cell. 

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 automated method differs from the ICSH method chiefly in that oxidation and ligation of heme iron occur after the hemes have been released from globin. Therefore, ferricyanide and cyanide need not diffuse into the hemoglobin and methemoglobin, respectively. Because diffusion is rate-limiting in this reaction sequence, the overall reaction time is reduced from approximately three minutes for the manual method to 3 —15 seconds for the automated method. Reaction sequences in the Coulter S + II and the Technicon H 1 and H 2 are similar. Moreover, similar reactions are used in the other Coulter systems and in the TOA and Unipath instmments. 

Perhaps the most useful method for determining particle distributions is that of electrical conductivity, the most widely used instrument is the Coulter Counter (named after the Inventors), although there are now other similar instruments on the market. Originally, this instrument was designed to measure blood corpuscles which are 2-8 p in size. It has proven to be very... 

Various techniques and equipment are available for the measurement of particle size, shape, and volume. These include for microscopy, sieve analysis, sedimentation methods, photon correlation spectroscopy, and the Coulter counter or other electrical sensing devices. The specific surface area of original drug powders can also be assessed using gas adsorption or gas permeability techniques. It should be noted that most particle size measurements are not truly direct. Because the type of equipment used yields different equivalent spherical diameter, which are based on totally different principles, the particle size obtained from one method may or may not be compared with those obtained from other methods. 

Just as a Coulter Counter or a flow cytometer can automate or at least increase efficiency in counting heterospecific pollen transfer, use of artificial germination media still is an effective method of screening for pollen allelopathy. The fundamental approach recommended has not changed much in the last decade, i.e. sequentially dilute extracts from non-macerated... 

Again, the majority of these parameters are interrelated and highly dependent on the method used to determine them. Red blood cell count (RBC), platelet counts, and mean corpuscular volume (MCV) may be determined using a device such as a Coulter counter to take direct measurements, and the resulting data are usually stable for parametric methods. The hematocrit, however, may actually be a value calculated from the RBC and MCV values and, if so, is dependent on them. If the hematocrit is measured directly, instead of being calculated from the RBC and MCy it may be compared by parametric methods. 

This is the classical method of carrying out particle-size analysis. Coulter supply two instruments—the Model ZM (video display optical) and the top-of-the-range multisizer—the latter having built-in video display of results. 

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. 

The 11 nm-sized Ti02 were crystallized using either hydrothermal or thermal methods from 100 nm, amorphous gel spheres. The Ti02 crystal and agglomerate sizes were determined by X-ray diffraction (Philip 1080) and transmission electron microscopy (JEOL JEM 2010), respectively. The surface area and chemistry of the nanostructured Ti02 were analyzed by nitrogen physisorption (Coulter SA 3100) and Fourier transform infrared spectroscopy (FTIR, Perkin-Elmer GX 2000). Metal catalyst was deposited by incipient... 

This method has been approved as an ASTM procedure (F316). The typical apparatus used is schematically illustrated in Figure 3.11. An instrument based on this method has been introduced by Coulter Electronics recently (Venkataraman et al. 1988). 

Methods development strategy for enantiomer analysis using the P/ACE MDQ chiral system, Application information A-1889A, Beckman coulter, www.beckman-coulter.com... 

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