The second mass flow controller introduces a helium flow into the combustion oven, which serves a as carrier gas for these combustion gases. Water (H2O) is removed in a water trap downstream of the combustion oven, and the helium flow transports the combustion gases through a gas chromatographical (GC) column which separates these constituents from each other. Then the gases are conveyed to a thermal conductivity detector (TCD) to quantitatively determine the amount of each of these gases, and in turn of the corresponding elements. The third mass flow controller supplies a helium gas flow to the thermal conductivity detector.
For the analysis of oxygen in a sample, the analyser needs to be operated in a reducing mode without supplying gaseous oxygen. Helium is still used here as sweep gas. The oxygen is converted into a compound that is separated in the chromatographical (GC) column to be detected by the thermal conductivity detector.
To be able to accurately determine the composition of very small samples, the Bronkhorst devices, EL-FLOW Base and MANI-FLOW solutions, can accurately and reproducibly control small gas flows in the range of 100 ml/min. Moreover, the compactness of the gas flow devices themselves makes them a very useful part of the analysis equipment to reduce the footprint in the lab, savings costs.
Prior to using flow controllers, the analysis equipment applied a pressure difference as a driving force for the combustion gases to be transported through the process. Indeed, the combustion analysis process is more accurate by using flow devices.
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