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      Application of Ultrasound in Extraction At present, the application of ultrasound in extraction has become increasingly widespread, and it has been industrialized in Chinese medicine extraction. The extraction of traditional Chinese medicines in my country has disadvantages such as large solvent consumption, long extraction time, high extraction temperature, long process route, and low extraction efficiency, resulting in high residual solvent content, low active ingredient content, difficult quality control, and poor efficacy in traditional Chinese medicine products. The main problems such as obvious problems, low product prices and weak competitiveness in the international market have greatly restricted the process of Chinese medicine modernization in my country.

      The use of ultrasound in the extraction of traditional Chinese medicines can significantly reduce solvent consumption, shorten the extraction time, and achieve high extraction rates at lower temperatures without destroying the effectiveness of traditional Chinese medicines. It can be widely used in the extraction of saponins, alkaloids, flavonoids, anthraquinones, organic acids and polysaccharides in traditional Chinese medicine.

The   its broken. At present, supercritical CO2 extraction has become a research hotspot in recent years due to its advantages of green and pollution-free, little or no residual solvent, less inactivation of active ingredients, and high product quality. But at the same time, this technology has the disadvantages of high extraction pressure, long time, low extraction rate, large amount of entrainer and high energy consumption, which greatly limit its industrial application.

      Using ultrasound in supercritical fluid extraction can significantly reduce the pressure and temperature of the extraction system, reduce the amount of entrainer and shorten the extraction time, and the extraction rate is also significantly improved. Riera E studied the extraction of oil from almond granules with ultrasonic enhanced supercritical CO2 fluid. The experiment used 20 kHz, 50 W ultrasound. The results showed that the extraction time of almond oil was shortened by 30% at the same extraction rate with the addition of ultrasound in supercritical CO2 compared with no additional ultrasound, while the extraction rate was increased by 20% at the same extraction time. In addition, the ultrasonic transducer can be used as a highly sensitive probe to display the phase behavior of supercritical fluids under lower power conditions.

      At present, the research on ultrasonic extraction is mainly limited to single-frequency ultrasound, and there are few studies on two or more multi-frequency ultrasonic irradiation to enhance extraction at the same time. Research in this area is a new topic that has only been put into research in recent years. Experiments have shown that dual-frequency and triple-frequency ultrasonic orthogonal irradiation can significantly increase the sonochemical yield. Due to the infancy of this research in China, many aspects of research, such as frequency selection, ultrasonic emission location layout, power Collocation and other aspects need to be further deepened. The author's laboratory is conducting research on the extraction of alkaloids from bitter wood by multi-frequency ultrasound, and has achieved promising phased research results.