Photothermal Lens-Based Trace Water Detection in Organic Solvents Using Quantum Cascade Laser as Pump Source

The photothermal lens technique has been used to determine optical, thermal, and mechanical properties of liquids [1], [2]. The infrared spectroscopy methods allow probing fundamental vibrational transitions, providing direct access to molecular-specific information. The strong optical absorption of water attributed to the H-O-H bending vibration at ~1645 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup>allows the detection of traces of water in organic solvents using an excitation laser with emission in the mid-infrared [3]. Determination of trace water content in solvents is important in many industrial applications, therefore a range of advanced sensing systems have been developed to address this need.