Topics - Quartz
Quartz is a very pure form of silica and is used in gas chromatography in the form of fused silica to construct capillary columns. Quartz is also employed in liquid chromatography for the construction of cell widows for UV detectors. Quartz is a very inert material and, thus, is ideal for the construction of capillary columns. Actually, capillary columns are rarely made from crystalline quartz but from pure, often synthetically produced, fused silica. Although fused silica is essentially very pure, the capillary columns are often first cleaned with hydrochloric acid to remove any remaining traces of metal ions which can affect the chromatographic performance The fused silica surface has now a considerable number of hydroxyl groups on the surface which can also cause peak distortion. These hydroxyl groups are then blocked by treatment with hexamethyldisilazane. Quartz is transparent to UV light from a wavelength of about 180 nm through the whole of the visible spectrum. It is thus ideal for use as windows in UV absorption cells. Quartz is also strong and windows only 2 mm thick can tolerate the high pressures used in liquid chromatography.