Simultaneous flow-injection flourimetric determination of ammonia and hydrazine with a novel mode of forming pH gradients

Automated fluorimetric sensor for hydrazine determination in water samples based on the concept of zone fluidics

In the present study, we report an automated fluorescence sensor for the determination of hydrazine in various water samples based on the concept of zone fluidics. Hydrazine and O-phthalaldehyde react through a unique mechanism in acidic medium (pH = 1.5) and without the presence of additional nucleophilic compounds. Another interesting feature of the proposed reaction is that it is not based on the Red/Ox properties of hydrazine, enhancing further the selectivity of the analytical procedure. The produced hydrazone exhibits high fluorescence at Ex = 318/Em = 376 nm. Using 120 s as a stopped flow step and temperature of 70 °C, we achieved satisfactory sensitivity for the determination of the analyte at a microgram per liter level with a limit of detection of 1.4 μg L^-1 and an analysis rate of 12 h^-1. The absence of matrix effect enabled the direct analysis of drinking (tap, mineral, table) and boiler feedwater samples with percent recoveries in the range of 91-111%.