One of the more interesting things highlighted is photoacoustic spectroscopy … really, exciting molecules with light and making them “scream.” Modulated or pulsed excitation is typically used, and detection of the pressure (heating from absorption) is accomplished with a sensitive microphone. One of the most successful recent implementations of this is by Gasera, who have patented a MEMs-based cantilever microphone that is both low-noise and highly sensitive. This has brought detection limits into the parts-per-billion range with photoacoustic technology for the first time. Current work is on flow-through cells to increase throughput.
Quantum Cascade Lasers (QCLs) are rapidly maturing, and devices incorporating QCLs are moving into commercial reality. As these sources have become more stable and reliable, they have started to compete with tunable diode lasers (TDLs)- which are also discussed in the article – for molecular analysis. TDLs operate in the NIR, where overtone transitions are weaker, but can still attain 10s of parts-per-million detection limits. QCLs promise to improve on these by orders of magnitude.
Look up the article and see what you think. Would love to hear your comments on it, please email me at steve “at” flashanalysis.com.