A dynamic ultrasound-assisted extraction method prior to the gravimetric determination of total fat content in bakery products was proposed (Ruiz-Jimenez J et al., Anal Chim Acta 2004, 502, 75).
Samples were inserted in a stainless steel extraction chamber drained by the extraction fluid (hexane). The tube was immersed in a water bath in which an ultrasonic probe (Branson 450 sonifier) was immersed.
After testing several parameters, the most efficient approaches was an open system where fresh extractant was pumped in forward-and-back steps. Two grams of sample were optimally extracted with 25 ml of hexane for a time much shorter than conventional Soxhlet extraction. Comparisons with the Folch reference method have shown no significant differences when food samples were extracted (Ruiz-Jimenez J et al., Anal Chim Acta 2004, 525, 159).