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Sensing of Water Dissolved in Solvents Using a 5.629 m Multimode Quantum Cascade Laser

Volume 62, Number 12 (Dec. 2008) Page 1349-1353

Ouvrard, A.; O'Dwyer, K.; MacCraith, B.D.

We report herein the detection of liquid water dissolved in a variety of solvents using a thermoelectrically cooled, pulsed, Fabry-Perot quantum cascade laser, operating at 5.629 μm at room temperature. The prototype sensor system consisted of the laser, a series of off-axis parabolic mirrors, and two mercury cadmium telluride detectors. When applied to the detection of water in tetrahydrofurane, a limit of detection of 0.85 parts per million was achieved. It is envisaged that such a sensor would be well suited to process control applications within the pharmaceuticals industry.