High-throughput Ru(III) analysis using the hydrothermal flow reactor-mediated FIA by the extreme acceleration of Ru(III) complexation with 1,10-phenanthroline

A new type of flow injection analysis (FIA) combined with a high-temperature reactor maintained at 100–400 °C, namely hydrothermal flow injection analysis (HT-FIA), has been successfully applied to high throughput determination of Ru(III) on the basis of a conventional chromogenic reaction with 1,10-phenothroline (phen). Although this classical chromogenic reaction using phen is sensitive and selective for Ru(III), the complex formation of Ru(phen)3 requires 2 h. The acceleration using HT-FIA is extraordinary high so that the determination reaction of Ru(III) was successfully shortened to 5 s at 150 °C, where the analytical procedure was accelerated more than 1000-fold. This enabled a high-throughput analysis of Ru(III) with 100 μL sample, of which at least 10 samples can be analyzed within 10 min. The detection limit of Ru(III) determined on the basis of 3 times of standard deviation was 5.3×10−7 M (53 pmol or 5.4 ng Ru in 100 μL sample). The present study emphasizes the importance of the revival of classical chromogenic reactions, which are potentially valuable but not regarded anymore as useful because they are time-consuming and tedious, to fit for the demand for environmentally harmless analytical techniques.