KIN-TEK Trace Source™ permeation tubes use a permeable membrane to dispense a small flow of chemical vapor. The most common type is a small tubular device that has liquid analyte sealed inside the tube. A very small but stable flow (nanograms-per-minute) of analyte vapor is emitted through the tube wall at constant temperature. The emission rate of the tube is determined by measuring the rate of weight loss. These tubes are used in KIN-TEK Gas Standards Generators to create dynamic gas standards with concentrations traceable to NIST through physical standards. Immersing the tube in a carefully controlled flow of inert dilution gas forms a trace concentration mixture of the analyte.
The emission rate of a permeation tube is dependent on the following factors:
- Physical characteristics of its permeable membrane.
- Permeability of its chemical analyte through the membrane.
- Temperature of the permeation tube.
- Partial pressure across its permeable membrane.
Each certified permeation tube is assigned a unique serial number and the certification data is kept on file for a minimum of two years.