Volatile Organic Compounds (VOCs) are organic substances in our environment that are volatile at room temperature. They can be emitted from a number of common materials, such as construction material, textiles, and adhesives. The link to harmful health effects of VOCs has resulted in an increased awareness and regulations to limit VOC exposure in various countries in recent years. Axetris mass flow meters (MFM) and controllers (MFC) are implemented in a number of analytical instruments which are used to detect and quantify VOCs, delivering key performance advantages.
VOC concentrations in the environment have a major impact on our well-being, comfort, and productivity. A number of countries have thus acted to set up new legislations to measure and control VOC emissions. The amendments to the Clean Air Act (CAA) of the United States and the “10 Measures for Environmental Protection” passed by the Chinese Government, initiated in 1990 and 2013 respectively, are important milestones in VOC regulation. Testing for VOC emissions from various materials, e.g. in automotive interiors, has gained importance across the world. Analytical techniques must provide sensitive and definitive measurements of VOCs in ambient air at sub parts per billion (ppb) concentrations to prove conformity to such legislations. Axetris mass flow meters (MFM) and controllers (MFC) are used in a variety of analytical instruments, such as gas chromatographs or air samplers, where they help achieve the required detection performance.
Key parameters to measure VOC concentration
Sorption rates of VOCs onto/from indoor surfaces are important factors driving their concentrations in the environment. VOC emission/sorption by indoor surfaces needs to be measured taking into account different key parameters such as the sorption coefficients, diffusion coefficients and the mass transfer coefficient through the boundary layer. An important prerequisite in achieving repeatable results is a high-performance flow measurement or control of the carrier gas used.
All about the right flow
Advantages over a wide range of analytical techniques
For sampling applications in VOC measurement, Axetris mass flow meters and controllers are often used in analytical techniques such as purge-and-trap, headspace and thermal desorption. For VOC quantification, gas chromatography (GC) is often applied, often in combination with a mass spectrometer (GC-MS) for analysis. Here again, high reproducibility of Axetris mass flow meters and controllers supports carrier and detection gas flow control.
Fur further information, read our application note on Gas Chromatography (GC) and our success story on how Axetris MFCs helped increase split ratio flexibility of a GC Injector 30-fold, to learn more about Axetris solutions.
Creating Standard Reference Samples
Axetris mass flow meters and controllers provide the accuracy and repeatability needed to produce standard reference samples. A standard sample is a mixture of known VOC concentration from liquid injection and/or bottled gas. Precise sample preparation to analyze for VOC concentrations requires highly reproducible mass flow controllers. Additionally, gas mixers that are used to create sample concentrations should be able to work across a wide flow range to allow for analytical flexibility. Because of this, besides delivering high precision and reproducibility, the mass flow controllers must work across a wide dynamic range and various performance parameters.