3. Sample Materials Handling
1. The heated valve contains a cartridge to hold the solid (or liquid) sample materials
The demountable stainless steel sample cartridge is inserted into the valve body. It is heated together with the valve. There are two gas filters at the inlet and outlet of the cartridge. The inlet and outlet filters are made of stainless steel sintered frit. These filters are designed to prevent particles (Solids or liquids) from entering the delicate valve mechanism. We recommend the use of binder free glass fiber filter paper:
inside both ends to immobilize further the sample. This is a must when using liquids sample. No sample droplets should enter the valve mechanism, so the liquid should be immobilized by soaking it in the glass paper!. Glass filter paper contains absorbed water, and should be dried over a hot plate before use. This Glass paper (1821-019 Grade GF/B discs, 19.1 mm, 50/pk is available from: http://www.whatman.com/GlassMicrofiberBinderFree.aspx)
Sample consumption is low (less than 0.1 mg per hour for 10Hz operation) so you do not need to overload the cartridge. Cleaning the cartridge when changing samples is achieved by ultrasonic rinsing in an alcohol or acetone bath. Binder free glass fiber paper is also available from other chemistry lab suppliers.
2. What materials are exposed to the gas?
The gas is exposed to Stainless steel parts, oxide ceramics and "Kapton" seals. This material selection allows the valve to be highly corrosive resistant. The corrosion resistance is such than when operated with dried gasses, even Fluorine or Ammonia can be used (at less than 10%) . Even small trace of water vapor (remaining adsorbed on the inner valve surfaces) can cause rapid corrosion. We recommend running the valve with DRY carrier gas for several hours before introduction of a corrosive gas mixture. Baking and long pumping time of the gas supply lines is also recommended. Halides can harm stainless steel alloys, especially those that are magnetic. We therefore do not recommend the uses of Halides (like Chlorine, Iodine and Fluorine or compounds that contain these halides) unless special care is taken (like using the halides in low concentration and dry conditions and short exposure times).
3. How long will the Kapton gaskets last?
The Kapton gaskets that seal the valve, are designed to be replaced by the user when worn out. Operating at room temperature or bellow, they should last for weeks of continuous use. The Kapton polymer is known for its resistance to most organic solvent, but is also known to be attacked by strong amines (like ammonia at high concentration).
4.Optional Quartz cartridge container, with build-in quartz sinter
The optional Quartz cartridge replaces the S.S. cartridge container, which is seated inside the rear part of the HT valves.The quartz cartridge slows down the decomposition of some sample molecules that can react with the stainless cartridge (and stainless sintered frit of the front filter) at higher temperatures.