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Cantilever-enhanced photoacoustic spectroscopy coupled with gas chromatography is used to quantitatively analyze a mixture of alcohols in a quasi-online manner. A full identification and quantification of all analytes are achieved based on their spectral fingerprints using a widely tunable continuous-wave laser as a light source. This can be done even in the case of interfering column/septum bleed or simultaneously eluted peaks. The combination of photoacoustic spectroscopy and gas chromatography offers a viable solution for compact and portable instruments in applications that require straightforward analyses with no consumables.

We report a photoacoustic spectroscopy setup with a high-power mid-infrared frequency comb as the light source. The setup is used in broadband spectroscopy of radiocarbon methane. Owing to the high sensitivity of a cantilever-enhanced photoacoustic cell and the high-power light source, we can reach a detection limit below 100 ppb in a broadband measurement with a sample volume of only a few milliliters. The first infrared spectrum of CH_414 is reported and given a preliminary assignment. The results lay a foundation for the development of optical detection systems for radiocarbon methane.

Hydrogen cyanide (HCN) in breath has been suggested as a diagnostic tool for cyanide poisoning and for cyanide-producing bacterial infections. To distinguish elevated levels of breath HCN, baseline data are needed. Background levels of HCN were measured in mixed exhaled air from 40 healthy subjects (26 men, 14 women, age 21–61 years; detection limit: 1.5 ppb; median: 4.4 ppb; range <1.5–14 ppb) by near-infrared cavity ring down spectroscopy (CRDS). No correlation was observed with smoking habits, recent meals or age. However, female subjects had slightly higher breath levels of HCN than male subjects. CRDS has not previously been used for this purpose.

We describe the design, construction, and initial performance evaluation of a high-repetition-rate cavity ringdown spectrometer. The spectrometer is based on the use of the Pound-Drever-Hall technique to lock the laser frequency to the maximum of a transmission fringe of the interferometer used as a sample cell. This results in continuous injection of light into the interferometer. The injection is repetitively interrupted with an acousto-optical modulator to generate ringdowns (exponential decays) at a typical rate of 10 kHz. Averaging of these large numbers of fitted ringdown times allows us to attain a minimum detectable absorption of 1.43×10^−11 cm^−1 Hz^−1/2 short term and 9.0×10^−11 cm^−1 Hz^−1/2 long term. In addition, the spectrometer has a continuous tuning capability of ∼1 cm^−1, which allows the use of standard linearization and frequency calibration techniques for the spectrum. To illustrate the operation and sensitivity of the spectrometer, part of the Q-branch of a weak acetylene overtone has been recorded.