Quartz Labware - Information and Care

Regardless of the supplier, all fused quartz used in ICP glassware begins life as sand, the majority of which is mined by the Unimin Corporation. In general, quartz tubing, rod and plate used in ICP and general labware are manufactured using one of two different manufacturing processes: Electric fusion and flame fusion. Electric fusion involves the heating of the raw material (sand) in a electrically heated crucible perched atop a five story tower. As the molten quartz exits the crucible, it travels through a hole of a specific dimension and around a "pin", also of a specific dimension, resulting in tubing of the desired dimension and tolerance.  Flame fusion involves the introduction of sand into a hydrogen/oxygen flame. Upon introduction into the flame, the sand melts and collects on a rod which is slowly removed from the flame, resulting in a solid quartz ingot.

Devitrification

Quartz exists in a state of imbalance. The atomic structure of quartz glass is a chaotic maze of atoms and atomic bonds. Devitrification is simply the quartz atoms rearranging themselves into an orderly, crystalline structure. Quartz only exists as a smooth, clear material because, during the manufacturing process, the atoms have difficulty rearranging themselves in an orderly pattern before the molten material cools into a solid material. Devitirification is caused primarily by two factors: contamination and atmosphere. Contamination, as it relates to quartz devitrification, typically refers to the introduction of alkali to the quartz. Alkali's include sodium, potassium and lithium and are usually introduced to the torch as a result of contact with the oils present in the skin. Fortunately, simply touching the quartz will not necessarily promote devitrification. A catalyst must be present to start the process. In the case of quartz, the catalyst is heat, specifically 1000 degrees C. It is interesting to note that contamination may also be introduced to the quartz by way of water. Water drops on the surface of the quartz may attract contaminants and, when dried, the contaminants may remain on the surface of the quartz.

Atmosphere also has an impact on devitrification. Quartz is manufactured in a partial vacuum and, as such, has an oxygen deficit. In order to re-crystalize, quartz requires a more perfect stoichiometry (a 1:2 ratio of silicon to oxygen in quartz). As the atmosphere contains a fair amount of oxygen, there is always oxygen present to promote devitrification, but adding additional oxygen will cause quartz to devitrify faster. Temperature also plays an obvious role in devitrification. As high temperatures are necessary to cause devitrification, the higher the temperature, the faster the quartz will devitrify. This explains why torches used in high temperature applications like oil labs tend to devitrify faster than those used in water labs.

Care and Handling of Quartz

Obviously, the best way to ensure long torch life is to avoid contamination.  Lab technicians should never touch the outer shield of an ICP torch with the bare hand. Additionally, rinsing a dirty torch in water, detergent or acid solution may result in either decreased performance or a broken torch. The heating and cooling cycle inherent to ICP operation places a tremendous amount of stress on the ICP torch and this, combined with any level of devitrification, can cause a torch to shatter instantly when placed in liquid. Though this may not be possible in all labs, we have found that the best way to clean an ICP torch is to bake the torch in a muffle furnace.  If you must clean your torch in a liquid bath please take great care.

Article Courtesy of Precision Glassblowing

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