Inexpensive spectrophotometric determination of nitrite with a laboratory-constructed flow cell

Abstract Nitrite is a carcinogenic substance and its measurement in water samples is important to protect mankind. Here we have introduced a simple and inexpensive fluidic system for the online determination of nitrite in water samples. For this purpose, a highly sensitive, optical flow cell detector was fabricated and used in a fluidic system to prepare a compact unit for nitrite monitoring. Safranin solution in acidic media was used in the system for the sensitive and selective determination of nitrite. In acidic media, nitrite reacted with safranin to form a diazonium salt which caused the dye in the solution to change from reddish-orange to blue. The safranin solution absorbance, which is related to nitrite concentration, was monitored by the fabricated photometer with the flow detector at 525 nm. Water samples were processed to evaluate the effectiveness of both the introduced system and the analytical procedure. Good analytical performance was obtained, including a linear response from 0.3 up to 3 mg/l nitrite (r = 0.9918) with a detection limit of 0.1 mg/l and a relative standard deviation of 4.24% (n = 10), using the proposed setup.