Abstract

Recent research has identified carbonyl sulfide (OCS) in expired human breath as a possible marker for liver disease and acute allograft rejection in lung transplant recipients [1,2]. This is an exciting possibility in that exhaled breath analysis may offer a non-invasive alternative to such procedures as transbronchial biopsies for diagnosing acute rejection [2]. However, there is a need to develop sensors capable of real-time, robust, and routine measurement of OCS at low- to mid- parts-per-billion (ppb) levels. Mid-infrared tunable laser absorption spectroscopy (TLAS) is a candidate technology on account of its molecular selectivity, rapid response times, and strong absorption intensities of OCS near 4.86 µm (>1 × 10⁻¹⁸ cm⁻¹/molecule _x cm⁻²). We report on the use of a near-room temperature pulsed quantum cascade (QC) laser based sensor to perform OCS measurements with ppb sensitivities. Isotopic selectivity was also demonstrated for ¹⁶O¹²C³²S and ¹⁶O¹²C³⁴S.

© 2003 Optical Society of America