Improved ruggedness for flow-based kinetic methods of analysis

This paper introduces a new approach to improve the ruggedness of flow-based kinetic determinations. After reagents and sample are mixed, the flow is stopped, signal vs. time data are recorded by an on-line computer, and curve-fitting methods are used to compute the signal that would be measured if the reaction were monitored to equilibrium. The new approach is evaluated using the Mo(VI) catalyzed oxidation of iodide to triiodide by hydrogen peroxide. Time-dependent concentrations of triiodide are monitored by changes in absorbance at 360 nm. Effects of changes in pH as well as the concentrations of iodide and Mo(VI) are evaluated using four different data-processing options, two of which were expected to exhibit poor ruggedness to changes in these variables and two of which were expected to exhibit significantly improved ruggedness. All data-processing options yielded linear calibration plots and had similar degrees of precision. As expected, the principal difference among the options was the ability to reject effects of changes in experimental variables. The new options are 10- to 70-fold less dependent on changes in pH and concentrations of iodide and molybdate than the more conventional options.