Calibration gases are vital for ensuring the accuracy of analytic systems and equipment, establishing a reference point to verify an analysis. Traditionally, gas cylinder standards have been used for applications such as calibration of gas monitoring systems and chromatographs, checking the accuracy of gas detectors, and generating known test atmospheres. But bottled trace level (ppb and ppm) standards can be costly, calibration cylinders can take up valuable lab space, and gas in stored cylinders can degrade over time.
Eliminating the challenges of working with bottled gases, VICI Metronics permeation tubes and other types of permeation devices provide a reliable, “plug-and-play,” traceable gas calibration solution. Permeation devices provide a stable concentration of a specific trace chemical, including those with low vapor pressures. The calibrant gas permeates through a proprietary membrane system and mixes with a carrier gas (such as nitrogen) at a controlled rate to obtain a known mixture in ppm or ppb (parts-per-million/-billion).
Permeation rates can be certified using standards traceable to NIST by the most basic and accurate laboratory procedure—measuring the gravimetric weight loss over a known time period at a known temperature. In fact, permeation rate data is already established for hundreds of different compounds, and rates for new compounds can be easily certified using NIST-traceable standards.
Multi-component gas mixtures can also be generated easily with NIST traceability using established EPA and ASTM protocols by using appropriate combinations of permeation devices. This technique also allows the removal of any single component from a gas mixture by simply removing the applicable permeation device. A wide range of concentrations can also be generated by simply varying the dilution flow rate and/or the setpoint temperature.