Particles magnetizable

This method was used, for example, for the solid-phase immunoassay of thyroxine (affinity chromatography). Various activation methods (CDI, periodate, and cyanogen bromide procedures) were compared with each other for coupling antibodies to magnetizable cellulose/iron oxide solid-phase particles. 211]... 

Motional magnetism, caused by rotation, vibration or translation of charged particles will be ignored. Thus all diamagnetism aspects will enter only implicitly. Thus we will not focus on static magnetic susceptibility theory (e.g. magnetizability) or measurements. 

Solid Phase Immunoassay, Use of Magnetizable Particles in (Pourfarzaneh, Kamel,... 

Laser printers and many copiers work by the one-component process, which allows the design of particularly compact machines. The principle of the magnetic brush is retained, however, the toner itself is magnetizable. This can be done by dispersing ca. 30-50 wt.% of black, magnetizable iron oxide particles in thermoplastic resins. Apart from the iron oxide, various additives are generally also incorporated to control the electrostatic chargeability, the flow characteristics and the color. The particle size of these toners is ca. 5-15 pm. 

To develop the magnetic-polarization model, note that an isolated magnetizable particle of radius a acquires a magnetic dipole m in the presence of a magnetic field H ... 

M. Pourfarzaneh, R. S. Kamel, J. Landon, and C. C. Dawes, The use of magnetizable particles in solid-phase immunoassay, Methods. Biochem. Anal., 28 267-295 (1982). 

Cortex Biochem has found interesting applications for magnetizahle particles in analytical fields. Particles of the analytic aid are prepared Ifom a combination of magnetizable materials (iron oxide) and absorbing material (e.g., charcoal, polyacrolein, ion exchange, cellulose). The particles are dispersed in a biological sample to selectively absorb required compounds. After absorption was accomplished, particles with absorbed substance are removed from solution by a magnetized rod. The materials are used for separation of enzymes, protein, cells or bacteria. 

There are examples in this book of fillers which have magnetic properties, but somebody in the act of inventiveness came to the conclusion that such material can be used for removing materials from their solutions and designed a composite which contains magnetizable particles attached to the various materials (e.g., selective adsobent of a particular material). By mixing this composite with a solution of material, material is adsorbed by adsorbent and removed from solution by a simple magnet. A new analytic technique was created which is very useful in pharmaceutical and biochemical research. 

Magnetizable particles were used in the separation of biochemical compounds. Magnetizable particles of iron oxide are produced on different supports capable of absorbing various biological substances which are then removed from suspension by a magnetic field (see more about this application in Chapter 2). 

Many solid-phase assays have been described using the so-called enhanced technology (T15). Solid phases have ranged from 6-mm-diameter beads (M32, TIO, Til, W18), coated tubes (T10-T12), microtiter plates (06, S3, T14, T16, W2), magnetizable latex particles (H12), micropins (T8, T15), and nitrocellulose discs (HI6). 

The various applications of monodisperse poly(styrene) latex particles require different particle diameters. For example, we have mentioned above the use of 3 jjia magnetizable particles. 

Since N and u(r) fix the Hamiltonian (H) they completely characterize an N-particle wavefunction. When N varies at constant o(/ the response of a system is measured by x and rj. A density response function can take care of the situation when the external potential changes at a fixed N. Response of a system in the presence of an external weak electric field F or a magnetic field B is explained in terms of polarizability (a) or magnetizability" ( ), respectively. They are respectively defined as... 

In heterogeneous FIA the separation step generally serves two functions firstly, the antibody-bound and free fractions are separated (a requirement of the assay), and secondly, interfering substances present in the sample are removed, resulting in an increase in sensitivity in many cases provided that adequate washing procedures are employed. Heterogeneous FIA techniques have been widely based on solid-phase systems commonly used solid-phase FIA techniques include (i) competitive, (ii) sandwich, and (iii) fluoroimmuno-metric assays. Typical supports that may well also find application in sensor development are polyacrylamide beads, magnetizable particles and polystyrene tubes (6). 

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