External gradient method

The analysis method employed is the patented external gradient method described in detail elsewhere (1,4). The overall instrument performance was evaluated using monodisperse polystyrene latex standards, covering a range from 0.176 urn to 1.09 pm, obtained from Dow Diagnostics, Indianapolis, Indiana. 

BLS). This paper describes a novel and alternative method for performing DCP analyses and in particular a new procedure for the formation of the spin fluid density gradient external to the DCP disc. This new patented method ( 3), known as the External Gradient Method (EGM), will be compared to the BLS method of analysis. The quantitative precision of the results obtained with EGM and BLS will be compared by statistical analysis.In addition, qualitative advantages of the EGM over the BLS method will be given. 

There are two basic methods used with the (fisc centrifuge instrumoits (a) buffered line start and (b) external gradient methods. 

In the external gradient method, the spin fluid density gradient is formed external to the disc and injected into the disc while the disc is spiiming. The externally formed spin fluid contains at least two miscible or partially miscible liquids of different densities in an incompletely mixed condition. 

Run Module The run module is used to set up the LC conditions, including the pump (e.g., gradient method), UV methods (e.g., wavelength), and autosampler (e.g., sequence setup). Apart from the LC, the method for radiochemical detection and the volume of liquid scintillant for radioactivity counting is also programmed in this module. The autosampler (as set up by the mn module) is used to trigger the Start Run for all other instruments through external contact closures. 

Holsworth, R. M. Provder, T. Stansbrey, J. J. "A Novel External Gradient Formation Method for Disc Centrifuge Photo-sedimentometry Particle Size Distribution Analysis" This Volume. 

External-Gradient-Formation Method for Disc Centrifuge Photosedimentometric Particle Size Distribution Analysis... 

Apart from the passive encapsulation methods, different active entrapment techniques are described in the literature. Nichols and Deamer (1976) prepared liposomes with a pH gradient across the membrane (acidic interior with respect to the external buffer). These liposomes efficiently incorporated several catecholamines added to the external buffer. The same technique has been used to concentrate doxorubicin (DXR) in pH gradient liposomes (Mayer et al., 1986b). 

DSPC/Chol (55 45) LUVs (diameter = 100 nm) are prepared as described in section Preparation of Sphingomyelin/Cholesterol (55 45) Large Unilamellar Vesicle by Extrusion [(Lipid) = 20 mM, volume = 5mL], using 350 mM citrate pH 4.0 as the hydration buffer, and 20 mM HEPES 1.50 mM NaCl pH 7.5 (HEPES-buffered saline) as the external buffer. In this case, the pH gradient is formed during the final dialysis step. It would also be possible to omit the final dialysis step and form the pH gradient by one of two common column methods. This could be desirable if the LUV... 

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