A miniaturized analyzer for the catalytic determination of iodide in seawater and pharmaceutical samples

A monolithic flow conduit was especially designed and coupled to a multisyringe unit (MSFIA) in order to develop a kinetic analytical method. The new device, denoted CHIP, integrates different functions in a reduced size including confluent mixing, reaction coil, and thermostating, which allowed minimizing the dimensions of the entire analyzer system. The CHIP-MSFIA was satisfactorily applied to the determination of iodide using the Sandell-Kolthoff reaction. The resulting system allows fast, simple and automatic analysis in seawater samples and a pharmaceutical preparation. By the use of an additional syringe, reagent blank, sample blank, unspecific interferences, and sample analyte concentration was evaluated by simply changing the mode of operation. The instrumentation and analytical procedures were optimized in respect of sensitivity. A limit of detection of 4.7 μg L(-1) and linear working range of 4.3-70 μg L(-1) were achieved. Two new modes of air bubble elimination were developed and employed in this work, leading to improved reproducibility (RSD %=1.5%) and method robustness. The accuracy of analysis for seawater samples was evaluated by an Add-Recovery test obtaining recoveries between 97 and 106%. For the quantification of iodide in the pharmaceutical sample, standard addition calibration was required. No significant differences between the found and the certified value were found. The entire analytical procedure lasted about 150 s enabling a measuring frequency of 23 h(-1).