title: A fluorescent nitrate sensing system using a reaction cartridge and titanium trichloride.
abstract: A simple and highly sensitive cartridge type nitrate sensing system was developed using titanium trichloride (TiCl(3)) in hydrochloric acid to reduce nitrate to ammonium ion. The system primarily consisted of a nitrate reduction section using titanium trichloride and an ammonia detection section. The nitrate was reduced in a simply made cartridge equipped with filter units and the resulting ammonium ion solution was directly introduced into a flow injection system, where it was neutralized to ammonia and allowed to react with o-phthalaldehyde (OPA). The isoindole thus formed was detected by virtue of its fluorescence, allowing quantitation of the nitrate in the initial sample. Our sensing system has a detection limit of 0.01 mg l(-1) and a dynamic linear range from 0.05 to 2.5 mg l(-1) with response times of less than 5 min for the entire procedure. The system had a relative standard deviation (RSD) of less than 2.56% after more than 30 consecutive measurements of 0.5 mg l(-1) NO(3)(-). The system is unaffected by FeCl(3), Na(2)SO(4) and NaCl at concentrations of 200 mg l(-1) or by biological oxygen demand (BOD) values as high as 110 mg O l(-1). The effects of reaction time and titanium trichloride concentration were also investigated. Furthermore, several river water samples were examined.
authors.affiliation: Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8904, Japan.
authors.forename: S J
authors.initials: SJ
authors.lastname: Cho
authors.forename: S
authors.initials: S
authors.lastname: Sasaki
authors.forename: K
authors.initials: K
authors.lastname: Ikebukuro
authors.forename: I
authors.initials: I
authors.lastname: Karube