Fused silica, properties

Table 8. Dielectric Properties of Synthetic Fused Silica ...

CE, another high performance separation technique, was also proved to be a powerful tool and an alternative for HPLC in the analysis of natural dyestuffs, even if its application in this field is still considerably limited. It could play an important role especially in the analysis of artworks, as it requires a very small volume of a sample solution (a few dozen nanolitres). In CE[ 10 14] separation of charged species is based on their different migration properties along the capillary tube which is in a constant electric field. Two platinum electrodes and both ends of a narrow bore (i.d. 25 100 pm) flexible fused silica capillary (usually 60 100 cm long) filled with a suitable conducting buffer are immersed in two... 

Rezac, J. P., Properties and Applications of Whispering Gallery Mode Resonances in Fused Silica Microspheres, PhD dissertation, Oklahoma State University, 2002... 

Capillary wall Generally, the most straightforward approach is to use an uncoated fused silica capillary. But sometimes this is not possible because of adsorption problems to the capillary wall, or other wall properties are needed to control the electroosmotic flow. In literature, there are multiple examples. Besides permanently coated capillaries, there are several descriptions of dynamic coatings available, e.g., triethanolamine, Triton X-100, Polybrene, and quaternary ammonium salts. The advantage of these dynamic coatings is that the coating can be renewed between injections, which could improve repeatability and reproducibility of the separation. 

Gas chromatographic analysis of the product (Hewlett-Packard fused silica, cross-linked methyl silicone capillary column, 25 m x 20 mm, column temperature 100-270°C, injection temperature 250°C) shows that the product is over 99% chemically and isomerically pure, (Z,E)-l-Phenyl-l,3-octadiene shows the following spectral properties IR (neat) cm 1640, 1595, 1490, 985 ... 

In addition to providing highly selective separations, there are a multitude of other desired characteristics that a gas chromatographic stationary phase should possess. These properties include high viscosity, low surface tension allowing for wetting of the fused silica capillary wall, high thermal stability, and low vapor pressure at elevated temperatures. The stationary phase solvent should also not exhibit unusual mass transfer behavior. 

Optical Applications. Vitreous silica is ideal for many optical applications because of its excellent ultraviolet transmission, resistance to radiation darkening, optical polishing properties, and physical and chemical stability. It is used for prisms, lenses, cells, windows, and other optical components where ultraviolet transmission is critical. Cuvettes used in scatter and spectrophotometer cells are manufactured from fused silica and fused quartz because of the transmissive properties and high purity (222). 

---