Cavity enhanced laser spectroscopy of oxidation chemistry: from the lab to the clinic

Professor Grant Ritchie, University of Oxford. Part of the Inorganic seminar series.

Radicals are ubiquitous in both the ambient atmosphere and atmospheric pressure plasmas and are intimately linked to the oxidising capacity of these environments. As such, there is widespread interest in the quantitative detection of these species. In this presentation I will describe several laser based cavity enhanced techniques with the necessary capabilities for probing small levels of transient species; these include optical feedback cavity enhanced absorption spectroscopy[1] and Faraday rotation spectroscopy[2].  Example data on the detection of peroxy radical (RO2) species are presented: HO2 in particular has been highlighted as an important intermediate, implicated in the production of reactive oxygen species in cold atmospheric plasma sources, and is integral to the complex chemical network which generates hydrogen peroxide as one of the by-products. Radicals are also of importance in medicine and I will also introduce our recently developed laser based analyser for monitoring oxygen consumption[3]. Here, laser absorption spectroscopy provides measurements of O2, CO2, and water vapour within the airway every 10 ms and the analyser is integrated within a novel respiratory flow meter that is an order of magnitude more precise than other flow meters. Such precision, coupled with the accurate alignment of gas concentrations with respiratory flow, makes possible the determination of O2 consumption by direct integration over time of the product of O2 concentration and flow. Clinical capability has been illustrated by recording O2 consumption during an aortic aneurysm repair. This device now makes easy, accurate, and noninvasive measurement of O2 consumption for intubated patients in critical care possible.


[1] Detection of HO2 in an atmospheric pressure plasma jet using optical feedback cavity-enhanced absorption spectroscopy. M. Gianella, S. Reuter, A. Lawry Aguila, J.H. van Helden, G.A.D. Ritchie, New Journal of Physics 18 113027 (2016).

[2] Intracavity Faraday Modulation Spectroscopy (INFAMOS): a tool for radical detection. M. Gianella, T.H. Pinto, X. Wu, G.A.D. Ritchie, J. Chem. Phys. 147 054201 (2017).

[3] In-airway molecular flow sensing: A new technology for continuous, non-invasive monitoring of oxygen consumption in critical care. L. Ciaffoni, D.P. O’Neill, J.H. Couper, G.A.D. Ritchie, G. Hancock, P.A. Robbins, Science Advances 2 8 e1600560 August (2016).