Particle manufacture

The development and optimization of porous supports for chromatographic applications have depended on advances in polymer chemistry together with advances in particle manufacturing technology. Separations that required hours or days to achieve with early SEC supports are now typically performed in less than an hour. The following description of various types of media is presented in the approximate chronological order in which the various media were developed. 

Drug delivery to the respiratory tract has been characterized in the past decade by an increase in knowledge of drug droplet or particle manufacture, behavior, aerosol dispersion, lung deposition and clearance. The number of diseases for which aerosol therapy may be applicable has increased dramatically. The pharmaceutical scientist is no longer limited to pulmonary diseases as therapeutic targets. Substantial progress has been made in every area of pharmaceutical aerosol science, and it is anticipated that this will ultimately lead to many new therapies. 

Many particle types contain functional groups that are built into the polymer backbone and displayed on their surface. The quantity of these groups can vary widely depending on the type and ratios of monomers used in the polymerization process or the degree of secondary surface modifications that have been done. Some common particle functionalities are shown in Figure 14.6. Many of these functionalized particles can be used to couple covalently biomolecules through the appropriate reaction conditions (Ilium and Jones, 1985 Arshady, 1993). For each type of particle, manufacturers may offer several different densities of functional groups for different applications. 

Dissolve the amine-containing ligand to be coupled in 5 ml coupling buffer at a concentration sufficient to provide a 1- to 10-fold molar excess of ligand over the maximal calculated carboxylate group concentration for the amount and type of beads used. For particle manufacturers reporting a carboxylate concentration in meq/g, this is equivalent to pmol/mg. 

Summary of Particle Manufacturing Techniques and Employed Polymers... 

Pig. 8.16 Mercury intnision in HPMCAS spray-dried particles manufactured at a Niro PSD4... 

In addition to particle manufacture, it is also possible to manipulate particles, thus enabling their movement between different chemical treatment zones [157,158] as well as sorting them by size [159-164]. Particle manipulation theories are not just useful in particle manufacture they can also be apphed to cell enrichment and purification procedures [165,166] or sample preparation [167] among others. 

The pores of the solid may be interconnected (accessible to fluid from both ends of the pores), dead-end (connected to the outside of the solid only from one end), or isolated (inaccessible to external fluid). The pores in most solids are neither straight nor of constant diameter. Catalyst particles manufactured by pressing powders containing micropores into pellets, with macropores surrounding the powder particles of a different order of magnitude in size, are said to be bidisperse [19]. 

Originally, iron powder from mill scrap was used in powder metallurgy. The soap was primarily iron oxide that would fall off the steel as it was being milled. The iron oxide dust was heated in a hydrogen atmosphere to reduee the oxide to iron particles. Manufacturers called the powdered metal iron sponge because numa-ous holes form in the particles when the oxygen escapes. 

---