The reliability of measurement results depends directly on the level of reliability of the calibration performed. The success of the calibration, on the other hand, depends on the availability of accurate and metrologically traceable calibration standards. In gas analysis, bottled static gas standards are traditionally used. However, reactive gases cannot be easily bottled and stored. To eliminate gas storage, we have developed a method to dynamically generate reference gases.
The reliability and metrological traceability of static gas mixtures stored in gas cylinders are generally well known and bottled reference gases are available through several commercial operators. However, the shelf life and availability of chemically active water-soluble compounds as a bottled reference gas is often challenging, even impossible. The compounds are reactive and tend to adhere to surfaces, resulting in poor stability and usability.
The dynamic reactive gas generation equipment developed at VTT MIKES is particularly well suited for chemically active water-soluble compounds. The known gas mixture produced by the equipment can be fed directly to, for example, a gas analyser or through the entire measuring system to perform the calibration of the sampling system. The storage step of the reference gas is eliminated, which reduces the measurement uncertainty and improves the reliability. The known gas mixture can be implemented with the desired target chemicals and concentrations. Typical concentration ranges range from ppm levels in the exhaust gases to ppb concentrations in the room air.
The developed equipment has applications both in laboratory conditions and in the calibration of field equipment and sensors. The dynamic calibration method has been successfully applied to oxidized mercury (HgCl2), acids and bases (ammonia NH3, hydrogen chloride HCl, hydrogen fluoride HF, amines) and formaldehyde in various applications, among others. In general, the method is suitable for water-soluble compounds.
Calibration service based on this method is available for customers at VTT MIKES. The calibration can be tailored, and measurement points and compounds selected according to the customer’s needs. Calibration, measurement, or test results are reported with traceability and measurement uncertainty data. Our national standard laboratories comply with ISO/IEC 17025 standard (General requirements for the competence of testing and calibration laboratories) and our management system is certified according to the ISO 9001 (Quality management) and ISO 14001 (Environmental management) standards.