Tao Zhimin, Goodisman Jerry, Souid Abdul-Kader
Department of Pediatrics, State University of New York, Upstate Medical University, 750 East Adams Street, Syracuse, New York 13210, USA.
J Phys Chem A. 2008 Feb 21;112(7):1511-8. doi: 10.1021/jp710176z. Epub 2008 Jan 30.
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.
一种用于测量水溶液中氧浓度的自制仪器，通过测量溶解在溶液中的钯卟啉配合物（磷光体）的磷光衰减率来进行测量，该磷光体每0.1秒用630纳米的光进行一次闪光。氧气浓度是衰减率的线性函数。该仪器用于研究连二亚硫酸盐（S2O42-）与氧气在25摄氏度和37摄氏度下的反应。结果发现，在25摄氏度下，反应中消耗的连二亚硫酸盐与氧气的比例为1.2±0.2，在37摄氏度下为1.7±0.1，这表明化学计量比与温度有关。在这两个温度下，氧气消耗的初始速率-d[O2]/dt，发现对S2O42-为1/2级，对O2为一级。这一发现与先前提出的机理一致：S2O42- <--> 2SO2-迅速达到平衡，并且SO2-在速率决定步骤中与O2反应。
