药学英语翻译

Havingbrieflyexaminedthestructureoforganicpackingsandthevariousroutesintheirmanufacture，themostimportantfeaturesmaybesummarizedasfollows:>Hydrophilicaswellaslipophilicorg... Having briefly examined the structure of organic packings and the various routes in their manufacture， the most important features may be summarized as follows: > Hydrophilic as well as lipophilic organic packings are synthesized with a controlled pore and surface structure depending on the type of monomer/comonomer and the polymerization reaction. Surface structure can be altered by controlled consecutive surface reactions. > In accordance with the bulk composition， polymer packings are stable across almost the entire pH range， particularly under strong alkaline conditions. > Chemical stability is affected by oxidizing and reducing solutions. > Although cross-linking reactions have been optimised in as much as rigid pressure stable particles can be manufactured， some remaining swelling property is often noted when changing the solvent composition in HPLC. > As in the manufacture of silica， porosity， pore size， and surface area of polymer packings can be adjusted over a wide range， and micro-， meso-， and macro- as well as non-porous beads are synthesized reproducibly. 3.2.4.2 Hydrophobic Polymer Stationary Phases The synthesis of cross-linked copolymers of styrene and divinylbenzene has been studied intensively and is well documented. The starting monomer is styrene， and divinylbenzene (DVB) is used as cross-linker. The amount of DVB can reach up to 55wt.%. At 55% DVB， the copolymer shows practically no swelling and possesses a permanent porosity. Figure 3.21 illustrates the network structure of poly(styrenedivinylbenzene) (St-DVB). Commercial products differ in bead size and pore size. There are even non-porous products on the market， designed for the rapid separation of peptides and proteins by reversed phase HPLC (Maa and Horvath， 1988). St-DVB copolymers are stable in the pH range 0–14. They find increasing application in the separation of low molecular weight compounds， peptides， and proteins by means of reversed phase chromatography (Tanaka et al.， 1987， Tweeten and Tweeten， 1986) and as parent materials for the synthesis of derivatized packings in interaction chromatography of biopoly-mers (Unger et al.， 1987， Regnier， 1987). Numerous other organophilic polymer packings have been synthesized for size exclusion and interactive HPLC after suitable derivatization. They are reviewed in depth by Mikes (1988).