Reagent generation for chemical analysis assisted by ultrasonic irradiation

Abstract

Few methods, such as coulometrics, have been developed to produce reagents in situ for analytical purposes. In this work the concept related to the generation of ultrasound-assisted reagents was exploited to yield oxidizing species in batch and flow systems of analysis.To evaluate the efficiency of ultrasound-assisted reagent generation, the conversion of Fe2þ to Fe3þ associated with the 1,10-ophenantroline spectrophotometric method was tested to compare the oxidizing power of the produced species from pure water and aqueous solutions saturated with CCl4 or CHCl3 irradiated ultrasonic waves. Irradiation processes were conducted with an ultrasonic bath (40 kHz and 140 W). The borosilicate reactor was used in the batch studies, while the PTFE tube reactor was used for setting up the flow system, with the temperature during irradiation being controlled using a thermostatic bath. The sonochemical production of oxidizing agents was demonstrated to be efficient for chemical analysis in batch and flow systems. This technique was exemplified by oxidation of iodide and ferrous ions. It was observed that after 120 min of sonication approximately 40 lg of Fe2þ was quantitatively oxidized to Fe3þ. Similar result was obtained by the irradiation of iodine in aqueous–organic medium.