Determination of oxonium ion using laser diode fluorimeter : (Blue purple(405 nm)-Green (532nm) using photodiode at 90° as a detector and I^- -IO3^- -H3O^+ system for quenching of fluorescence

A newly developed sensitive, fast and accurate analytical method characterized by a sensitive, fast and accuracy for the determination of oxonium ion by laser diode fluorimeter-flow injection analysis. The method is based on the libration of free iodine causing to quench the fluorescence light (continuous fluorescence from fluorescien molecule (free acid)) when irradiated by laser source at 405nm. Chemical and physical parameters were studied and optimized. The optimum parameters were 1.3mL/min using fluorescien (free acid) as a carrier stream, 35μL sample volume at valve no.1 and 39μL at valve no.2 and opened valves sequentially. Data treatment shows that linear range 0.002-0.1mMol.L^-1,0.01-0.2mMol.L^-1,0.002-0.5mMol.L^-1,0.002-0.7mMol.L^-1 for HCl, H2SO4,HClO4 and tartaric acid respectively, with correlation coefficient r= 0.9562, 0.9976. 0.9755 and 0.9579. The limit of detection (S/N=3) 1.28ng/sample, 17.16ng/sample, 3.52ng/sample and 5.25ng/sample for HCl, H2SO4,HClO4 and tartaric acid respectively from the stepwise dilution for minimum concentration of lowest concentration in linear dynamic range of the calibration gragh. RSD% for the repeatability (n=8) was 1% for the determination of HCl, H2SO4,HClO4 and tartaric acid with concentration 0.01mMol.L^-1 . The comparison was made between the newly developed method analysis with the classical method (pH-meter) using the standard addition method via the use of paired t-test was studied at two different paths .First path a comparison between two methods of analysis and second path between the two different acids. It was noticed that there was no significant difference between different acids and different methods at 95% confidence interval level.