Abstract: Different oxidation methodologies based on ozone and focused ultrasound for the degradation of organic matter and organic-mercury compounds (spiked) present in human urine are discussed. Inorganic and total mercury can be determined in human urine. A flow-injection cold-vapor atomic absorption spectrometer system was used for mercury measurements. Optimization of cold vapor generation was performed with NaBH4 and SnCl2. A two-level full factorial design (24) was applied to understand the cross-effects among the variables influencing the degradation of organic-mercurials and organic matter in urine by KMnO4/HCl/focused ultrasound, namely, KMnO4 and HCl concentration, ultrasonication time and ultrasonication amplitude. Optimization results showed that all variables were significant. New trends in the application of focused ultrasound and ozone are highlighted. As a result of the optimization procedure, one simple, rapid and accurate method was developed for the determination of total mercury in urine samples. The method is based on the ultrasound assisted degradation of organo-mercurials and organic matter in urine in the presence of KMnO4/HCl/Focused Ultrasound. The procedure can be accomplished within 3 min, using 50% sonication amplitude provided by a probe ultrasonic device (63 W maximum output power, 22.5 kHz frequency). The method was applied to measure the mercury content in spiked urine from different non-exposed volunteers.

Abstract: A new method for the chemical oxygen demand (COD) determination assisted by ultrasonic radiation has been evaluated for the first time. The suggested method uses an instrumentation simpler and cheaper than the previous ones used for the same purpose. With this preliminary version of the method the optimized experimental conditions are: high ultrasonic power (143 W, 95% of maximum nominal power; 126.5 W/cm(2) of power density); high sulphuric acid concentration (>60%); and a sonication time of 2 min. Under these conditions this first prototype shows the same limitations as the official COD method as regards the type of organic compounds. It works successfully with easily oxidative organic matter (sodium oxalate, glucose and salicylic acid) but the COD values obtained with more difficult organic matter are poor. When the ultrasonic assisted method is applied to real waste waters the precision is statistically not different to that of the conventional semi-micro method but the COD values obtained lie between 50 and 60% of the values obtained with the conventional semi-micro method. Hence, the use of the ultrasonic radiation for COD determination seems to be an interesting and promising alternative to the conventional ones but still much more research efforts must be done in order to improve the instrumental set-up. The suggested direction of these developments must be a more efficient interaction between the ultrasonic radiation and the sample.

Abstract: A systematic study on the ultrasonic irradiation effect in the impregnation-reduction (I-R) process for preparing a Pt/Nafion(R) electrode was carried out in a flow injection system of ammonium ion detection. Both the impregnation and the reduction stages were affected by ultrasonic irradiation which increased the sensing currents of electrodes. Moreover, the effect of ultrasonic irradiation was found more significant in the reduction process than in the impregnation process. The relationship between sensing current and power of ultrasonic irradiation was also obtained. The specific active surface area of the Pt/Nafion(R) electrodes were evaluated by the cyclic voltametric technique. Meanwhile, the surfaces of the electrodes were characterized by XRD and SEM.