Sonochemistry reproducibility

It is often difficult to compare the sonochemical results reported from different laboratories (the reproducibility problem in sonochemistry). The sonochemical power irradiated into the reaction system can be different for different instruments. Several methods are available to estimate the amount of ultrasonic power entered into a sonochemical reaction, the most common being calorimetry. This experiment involves measurement of the initial rate of a temperature rise produced when a system is irradiated by power ultrasound. It has been shown that calorimetric methods combined with the Weissler reaction can be used to standardize the ultrasonic power of individual ultrasonic devices. ... 

Thermal probe systems are inexpensive, easy to handle in almost all ultrasonic devices and particularly those used in sonochemistry. Field distributions and optimization of the geometry of the system can be rapidly obtained and the accuracy of the method is high enough to ensure reproducibility. Chemists who make use of ultrasonic equipment should, as a very minimum, consider this method to calibrate and optimize sonication conditions prior to carrying out sonochemical reactions. 

In order to obtain accurate and reproducible results, temperature and pressure should be carefully monitored. These mechanical effects tend to increase to a maximum and then decrease to zero with the upper limits defined by the boiling point of the solvent and a hydrostatic pressure at ambient equal to the peak acoustic pressure. This is also the normal pattern in sonochemistry [6,7,117,118],... 

Since this chapter appears in a volume devoted to sonochemistry, chemical probes would appear to be the most attractive since they could allow direct comparisons with other chemical reactions. Chemical dosimeters are generally used to test the effect of an ultrasonic device on the total volume of the reactor. Local measurements can however be made with very small cells containing the dosimeter which could be moved inside the reaction vessel as with a coated thermocouple. Most of these chemical probes are derived from reactions carried out in an homogeneous medium, e.g. Weissler s solution, the Fricke dosimeter, or the oxidation of terephthalate anions. Among these the latter shows promise in that despite the fact that to date it has been much less used than Weissler s reaction it seems to have higher sensitivity and better reproducibility. 

A major point in sonochemistry is reproducibility, which is relatively easy to obtain within a laboratory because of internal consistency (the technical parameters remain constant). It is somewhat more difficult to obtain between different laboratories since experimental conditions are unlikely to be identical. Minor changes like the shape of the glassware or its volume can lead to different results, and so a careful scrutiny of the exact laboratory conditions for an experiment is essential. Unfortunately, a complete and exhaustive description of an ultrasonic system is rather difficult to obtain from the literature because the... 

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