Silanol Deactivation Procedures

For maximum column performance, blank or raw fused-silica tubing must receive pretreatment prior to the final coating with stationary phase. The purpose of 

Inert stainl ss steel equivalent to Stabllwax fused silica columnsi 

0 lit on-column Injection of neat paratin wax In methylene chloride. Oveh temp. 100 °C to 400 °C 10 °C/min. (hold 20 mih.). 

Ihjeotor type hP cool on-oolumn pressure programmable 

A variety of agents and procedures have been explored for deactivation purposes (26-40). For subsequent coating with nonpolar and moderately polar stationary phases such as polysiloxanes, fused silica has been deactivated by silylation at elevated temperatures, thermal degradation of polysiloxanes and polyethylene glycols, and the dehydrocondensation of silicon hydride polysiloxanes (37,41-45). 

---

One approach to solving the problem of residual silanol interactions has involved improvements in the synthetic procedures for the production of hydrocarbonaceous stationary phases. One synthetic approach for the elimination of residual silanol groups involves the reaction of the bonded phase with a small silylating reagent such as trimethylchlorosilane which is presumed to have easier access to silanol groups than bulkier, long-chained chlorosilanes. An alternative, synthetic approach involves surface polymerization of the stationary phase, which is believed to reduce the accessibility of surface silanol groups to polar analytes in the mobile phase. Stationary phases produced by the former method are often referred to as end-capped and stationary phases produced by the latter method are sometimes called base-deactivated. ... 

The most popular fabrication method of soKd sihcone nanoparticles is, however, emulsion polymerization or polycondensation. Figure 4.5 depicts the synthetic route, which can be used to obtain nanoparticles using this approach. The synthesis follows a two-step procedure. (1) In the first step the precursor is solubiHzed in the micelles to form an emulsion and the solidification process is performed. (2) Next, nanoparticles are isolated from surfactant, concomitantly with the endcapping procedure to deactivate silanol groups on the surface. 

The nanoparticles with a core-shell architecture are mainly prepared using the solidification in emulsion approach, as shown in Figure 4.5. The first step of the synthesis is the preparation of a surfactant-stabilized dispersion of uniform solid particles, as described in Section 4.2.1. These nanoparticles are treated as cores. Next, new precursors are introduced to the dispersion and solidification process is carried out. Finally, the nanopartides are isolated from the surfactant concomitantly with the end-capping procedure to deactivate silanol groups on the surface. As a result, the particles exhibiting heterogeneous structure are obtained. They consist of a solid core surrounded by a silicone shell. 

---