The detection of volatile organic compounds is of great importance for assessing the quality of water. In this contribution, we describe a miniaturized stripping device that allows fast online detection of organic solvents in water. The core component is a glass microfluidic chip that facilitates the creation of an annular-flowing stream of water and nitrogen gas. Volatile compounds are transferred efficiently from the water into the gas phase along the microfluidic pathway at room temperature within less than 5 s. Before exiting the microchip, the liquid phase is separated from the enriched gas phase by incorporating side capillaries through which the hydrophilic water phase is withdrawn. The gas phase is conveniently collected at the outlet reservoir by tubing. Finally, a semiconductor gas sensor analyzes the concentration of (volatile) organic compounds in the nitrogen gas. The operation and use of the stripping device is demonstrated for the organic solvents THF, 1-propanol, toluene, ethylbenzene, benzaldehyde, and methanol. The mobile, inexpensive, and continuously operating system with liquid flow rates in the low range of microliters per minute can be connected to other detectors or implemented in chemical production line for process control.
Microfluidics Open loop stripping Water monitoring Volatile organic compounds Process analytical technology
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We thank Valentian Arima and Ross Rinaldi (CNR Lecce, Italy) for providing the glass chip, Stefan Schmid (ETH Zurich) for providing the gas detector, Oliver Lade (Siemens AG Berlin) and Alexander Schocker (BASF Schweiz AG) for helpful discussions, and Tom Robinson for careful proofreading of the manuscript. The authors acknowledge the EU project Radiochemistry on chip “ROC”, grant agreement no. 213803 for financial support.
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