Public Research Seminar by Sustainable Energy and Environment Thrust, Function Hub, HKUST(GZ) - Particle Into Liquid Sampling For Real Time Oxidative Potential Measurement

WHO has estimated that atmospheric pollution is responsible for more than 7 million premature deaths each year. A large contributor to this mortality is due to atmospheric particulate matter (PM), with PM being linked to lung cancer, cardiovascular disease, and lung disease. A proposed mechanism to explain these health outcomes is through oxidative stress, wherein PM generated through combustion processes introduce a group of free radicals known as reactive oxygen species (ROS) to the body. These ROS impede cell function creating oxidative stress, which can lead to inflammation and cell death.

To investigate this hypothesis, instrumentation to accurately measure particulate matter ROS concentrations, or the oxidative load of particles, are essential. The ideal system should be: sensitive to a wide range of species; collect ultrafine PM with high efficiency; and collect and measure rapidly. Quantification of ROS is a difficult problem both chemically and physically. In order for measurement to take place, PM containing ROS must in most cases be collected into a liquid containing a chemical probe. The degree to which this probe reacts with the PM sample is measured in order to ascertain a value for the concentration of ROS, which is termed oxidative load.

Beyond the implementation of a chemical probe, there are several properties of ROS and combustion aerosols which make oxidative load measurements difficult. The high reactivity of ROS causes them to react readily with the atmosphere and other surroundings; leading to ROS on ultrafine particles having estimated half-lives of under 15 minutes. Therefore, delays between capture and measurement typical of filter collection methodologies can lead to significant underestimations in ROS concentrations. This indicates that the best approach for ROS measurement is to collect particles directly into liquid for analysis and immediately apply a chemical probe.

To address the above challenges, at QUT we have developed a real-time system that captures particles directly into a liquid containing an in-house developed probe based on a profluorescent nitroxide. In this presentation an overview of particle into liquid sampling for ROS measurements will be presented together with more detailed results from the QUT prototype.