Lesser known ultrasound-assisted heterogeneous sample-preparation procedures

Ultrasound (US) energy is gaining growing acceptance in sample-preparation (SP) steps, such as leaching and digestion; nevertheless, US is less accepted by analytical chemists in a number of other SP steps, either because the effect of US in them is not well known (e.g., liquid–liquid extraction) or because the steps are less common in SP (e.g., filtration, defoaming and degassing). An overview of the mechanisms of US effects in these steps, the potential of US-related variables for manipulating a given step and some key applications that can help analytical chemists to decide when US energy can benefit the step under study is here given.