Development of an Analytical Method for Nitric Oxide Radical Determination in Natural Waters

Abstract

The measurement of photochemically generated nitric oxide radicals (NO) in natural waters has long been an arduous task because of a lack of simple analytical techniques, even though the environmental significance of this radical is paramount. We have developed a simple analytical method for the determination of photochemically generated NO in natural waters using 4,5-diaminofluorescein (DAF-2) as a probe compound. This method is based on the reaction of photoformed NO with DAF-2 in air-saturated solution to produce a highly fluorescent triazolofluorescein (DAF-2T) product. DAF-2T was determined by using reversed-phase HPLC with fluorescence detection, with excitation and emission wavelengths of 495 and 515 nm, respectively. Under optimum conditions, the calibration curve exhibited linearity in the range of 0.025-10 nM DAF-2T. The coefficients of variance for the measurements of the signal intensities of DAF-2T (from the photolysis of 0.5 microM and 5 microM NO(2)(-) with DAF-2) were less than 5% and 3%, respectively. For a total irradiation time of 30 min, the detection limit of the photoformation rate of NO was 1.65 x 10(-13) M s(-1), defined as 3sigma of the lowest measured DAF-2T concentration (0.025 nM). The proposed method is relatively unaffected by potential interferents in seawater. The method was employed to determine the photoformation rate of NO in the Seto Inland Sea and the Kurose River in Hiroshima Prefecture, Japan. The measured NO photoformation rates in seawater and river water samples ranged from (5.3-32) x 10(-12) M s(-1) and (9.4-300) x 10(-12) M s(-1), respectively.

Chemical Dosimetry System for γ-Ray Irradiation Based on the Formation of Phenol from Aqueous Benzene Solutions

“…Short-life-time reactive oxygen species and radicals, such as hydroxyl radicals, 4,5 NO radicals, 6,7 hydrogen peroxide, 8 and hydrate electrons, 8 are photochemically generated in environmental water by natural sunlight. The author and coworkers have investigated and described a determination technique for some reactive oxygen species and radicals.…”

“…The author and coworkers have investigated and described a determination technique for some reactive oxygen species and radicals. [4][5][6][7][8] For the determination of hydroxyl radicals, many chemical probe methods based on the determination of products formed by reactions between hydroxyl radicals and probe compounds have been reported. In these methods, benzene, 4,5,9 nitrobenzene, 10 benzoic acid, 11,12 terephthalate, 13 2-propanole, 13 methanol 11 and dimethyl sulfoxide 14 were used as the probe compounds.…”

Photooxidative Degradation of Pesticides in Water; Response Surface Modeling Approach

“…Their CAS numbers, formulas, chemical structures, used abbreviation in the study, as well as reaction rate constants with hydroxyl (HO•) and sulfate (SO 4 • -) radicals are summarized in the Table 1 [15,18,26]. Chemicals used as constituents of mobile phases for high performance liquid chromatography (HPLC) were methanol (CH 3 OH, HPLC grade, JT Baker, USA), acetonitrile (CH 3 CN, HPLC grade, JT Baker, USA), ammonium acetate (CH 3 COONH 4 , 98 %, Sigma Aldrich, USA) and ultra-pure water obtained from Millipore Direct-Q UV 3 system, Merck, USA.…”

An improved method for the determination of dissolved nitric oxide (NO) in seawater samples

“…The detection limits range from 0.0015 Ward and Zafiriou, 1988 Chemiluminescence 0.25 This study * LOD for the conversion product from the reaction of NO with the trapping compound to 140 nmol L −1 . (Please note that the fluorometric detection of NO as described by Olasehinde et al, 2009, is suitable only for formation rates of NO from NO − 2 ). The sensor of Schreiber et al (2008) was developed for sediments but works in seawater samples as well.…”