Ultrasound-assisted liquid sample preparation involving chemical reactions

Ultrasound-assisted liquid sample preparation involving chemical reactions 

Any system involving a homogeneous liquid in which bubbles are produced is strictly not homogeneous in sonochemistry, however, it is not unusual to deem systems under ultrasound homogeneous. Sonochemical effects generally occur inside the collapsing bubble, where extreme conditions are produced, or at the interface between the cavity and the bulk liquid, where the conditions are far less extreme, or in the bulk liquid immediately surrounding the bubble, where the dominant effects are mechanical in nature. 

Derivatization has been assisted by US in some cases, both in continuous [30] and in batch approaches [31] and provides substantially improved product formation in all cases. Because the US was intended to improve a reaction, the origin of the effect was generally not studied and the effect was occasionally ascribed to degassing by US [31]. 

The accelerating effect of US on the determination of phosphate by the Molybdenum Blue method was ascribed to depolymerization of molybdate, which was thought to speed up its reaction with phosphate and inorease the sensitivity [32]. 

Biocatalysed reactions assisted by US have mainly to do with enzymatic digestion [9], These processes, which can involve solid, liquid and heterogeneous samples, arefarfrom real digestions as only the target analytes are removed, the remaining sample components preserving their appearance, in most cases. This is a relatively novel use of the US-enzyme couple, particularly in hydrolysis reactions [33]. By contrast, US assistance to the joint use of enzymatic catalysis and supercritical fluids, which has aroused much analytical interest [34], continues to be unexplored as yet. 

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