title: Oxygen measurement via phosphorescence: reaction of sodium dithionite with dissolved oxygen.
abstract: A homemade instrument for the measurement of oxygen concentration in aqueous solutions measures the decay rate of the phosphorescence of a Pd-porphyrin complex (phosphor) dissolved in the solution, which is flashed every 0.1 s with 630 nm light. The concentration of O2 is a linear function of the decay rate. The instrument is used to study the reaction of dithionite (S2O42-) with O2 at 25 degrees C and 37 degrees C. It is found that the ratio of dithionite to oxygen consumed in the reaction is 1.2 +/- 0.2 at 25 degrees C and 1.7 +/- 0.1 at 37 degrees C, suggesting a temperature-dependent stoichiometry. At both temperatures, the initial rate of O2 consumption, -d[O2]/dt, is found to be 1/2 order in S2O42- and first order in O2. This finding is consistent with a previously proposed mechanism: S2O42- <--> 2SO2- comes to a rapid equilibrium, and SO2- reacts with O2 in the rate-determining step.
authors.affiliation: Department of Pediatrics, State University of New York, Upstate Medical University, 750 East Adams Street, Syracuse, New York 13210, USA.
authors.forename: Zhimin
authors.initials: Z
authors.lastname: Tao
authors.forename: Jerry
authors.initials: J
authors.lastname: Goodisman
authors.forename: Abdul-Kader
authors.initials: AK
authors.lastname: Souid
mesh_terms: D004227:Dithionite / Q000737:chemistry*; D007700:Kinetics; D008163:Luminescent Measurements; D009942:Organometallic Compounds / Q000737:chemistry; D010100:Oxygen / Q000032:analysis* / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry; D012995:Solubility; D013997:Time Factors
chemical_list: D009942:Organometallic Compounds; D004227:Dithionite; D010165:Palladium; D010100:Oxygen