On-line dilution and detection of vainillin in vanilla extracts obtained by ultrasound

A continuous flow method coupling the dilution of extracts, obtained by application of ultrasound, and the on-line detection of vanillin is proposed. The flow method allowed the quantification of vanillin in a range between 200 mg l−1 and 2000 mg l−1 with a repeatability and reproducibility of 3.79% and 3.03%, respectively, for a standard of 1200 mg l−1. The extraction conditions such as irradiation power, irradiation time, non-irradiation time and number of cycles are some of the most significant conditions in the vanilla extraction by ultrasound assisted extraction (USAE). The obtained results were compared with other conventional extraction methods: Soxhlet and maceration in accordance with the Mexican official method. The results showed that with the application of the USAE the extraction efficiency was increased between 19% and 72% in comparison with Soxhlet and maceration, respectively, besides, the extraction time decreased between 83% and 98%.