[eng] Reactive oxygen species (ROS) are highly reactive molecules which might be
divided in two types: free oxygen radicals (e.g. O2
·−, ·OH) and non-radical ROS
(e.g. H2O2,
1O2). ROS are naturally generated in both biological and marine
systems, but the homeostatic levels may be altered. In fact, the alteration of ROS
levels in biological systems can trigger oxidative stress, associated with the
damage of biomolecules like proteins, lipids, or nucleic acids. This work aims at
developing a suitable automatic analytical methodology able to reliably quantify
ROS at the concentration levels expected in seawater and biological samples,
such as saliva. For this purpose and taking into account the unsteadiness, and
low concentrations of ROS in the studied matrices, a flow-through system with
flash chemiluminescence (CL) detection based on the luminol chemistry has
been resorted. In order to improve the conventional spirally-shaped CL detection
flow-cell with cylindrical cross-section, 3D printing technology has been chosen
for rapid and simple prototyping and production of complex designs at low cost.
Hence, four 3D printed flow-cells with novel cross sections geometries:
semicylindrical, pyramidal shape, cubic and 5-side prism, were evaluated and
compared with the cylindrical one with the aim of enhancing the capture of the
elicited light from the flash CL reaction by maximizing the liquid volume close to
the detection system. In addition, three different reagent/sample confluence types
were included in the 3D printed cell design: T, Y and a modified Y types.
Computer flow dynamic simulations were also performed to investigate the flow
field for the distinct designs and get knowledge on the mixing performance and
the magnitude of the flow rates versus position at the inlet of the flow cell. Other
chemical and hydrodynamic parameters of the flow-through system were also
studied (reagent pH, in-situ preparation of the chemilumogenic reagents,
reagent/sample flow-rates, blank signal minimization, injection volume and
dispersion effect throughout the flow conduits). Finally, the optimal 3D printed
flow-cell (5-side prism cross-section with Y confluence type) in combination with
the optimized methodology was applied to the determination of hydrogen
peroxide, as a model analyte, in saliva and seawater matrices.