超聲波萃取的原理
超聲波是指頻率為20kHz-50MHz的電磁波,它是一種機械波,需要能量載體一一介質來進行傳播。其穿過介質時,會產生膨脹和壓縮2個過程。超聲波能產生并傳遞強大的能量,給予介質極大的加速度。這種能量作用于液體時,膨脹過程會形成負壓。如果超聲波能量足夠強,膨脹過程就會在液體中生成氣泡或將液體撕裂成很小的空穴。這些空穴瞬間即閉合,閉合時產生高達3000MPa的瞬間壓力,稱為空化作用。這樣連續不斷產生的高壓就像一連串小爆炸不斷地沖擊物質顆粒表面,使物質顆粒表面及縫隙中的可溶性活性成分迅速溶出。同時在提取液中還可通過強烈空化,使細胞壁破裂而將細胞內溶物釋放到周圍的提取液體中。利用超聲波的上述效應,從不同類型的樣品中提取各種目標成分是非常有效的。
Ultrasonic wave refers to the electromagnetic wave with frequency of 20khz-50mhz. It is a kind of mechanical wave, which requires energy carrier -- medium to propagate.As it passes through the medium, it expands and compresses.Ultrasonic waves can generate and transfer powerful energy, giving the medium a great acceleration.When this energy is applied to a liquid, a negative pressure is formed in the expansion process.If the ultrasonic energy is strong enough, the expansion process will create bubbles in the liquid or tear the liquid into small holes.These holes are closed instantaneously, and the instantaneous pressure up to 3000MPa is generated when they are closed, which is called cavitation.In this way, the continuous high pressure is like a series of small explosions that continuously impact the surface of the particles and rapidly dissolve the soluble active components in the surface and cracks of the particles.At the same time, the intracellular solute can be released into the surrounding extractive liquid by the strong cavitation of the extractive liquid, which causes the cell wall to break.It is very effective to extract various target components from different types of samples by utilizing the above effect of ultrasound.
技術特點
與常規的萃取技術相比,超聲波萃取技術快速、價廉、高效。在某些情況下,甚至比超臨界流體萃取(SFE)和微波輔助萃取還好。與素氏萃取相比,其主要優點有:①成穴作用增強了系統的極性,這些都會提高萃取效率,使之達到或超過素氏萃取的效率;@超聲波萃取允許添加共萃取劑,以進一步增大液相的極性③適合不耐熱的目標成分的萃取:④操作時間比素氏萃取短。
超聲波萃取優于SFE體現在:0儀器設備簡單,萃取成本低得多;@可提取很多化合物,無論其極性如何,因為超聲波萃取可用任何一種溶劑。SFE事實上只能用CO2作萃取劑,因此僅適合非極性物質的萃取。超聲波萃取優于微波輔助萃取體現在:①在某些情況下,比微波輔助萃取速度快;②酸消解中,超聲波萃取比常規微波輔助萃取安全3多數情況下,超聲波萃取操作步驟少,萃取過程簡單,不易對萃取物造成污染。對于超聲波萃取來說,提取前樣品的浸泡時間、超聲波強度、超聲波頻率及提取時間等也是影響目標成分提取率的重要因素。
Compared with conventional extraction technology, ultrasonic extraction technology is fast, cheap and efficient.In some cases, it is even better than supercritical fluid extraction (SFE) and microwave-assisted extraction.Compared with element extraction, its main advantages are: (1) acupoint effect enhanced the polarity of the system, these will improve the extraction efficiency, make it reach or exceed the efficiency of element extraction;Ultrasonic extraction allows the addition of co-extraction agent, to further increase the polarity of the liquid phase (3) suitable for the heat resistance of the target component extraction: (4) the operation time is shorter than the element extraction.
Ultrasonic extraction is superior to SFE in the following aspects :0 simple equipment, much lower extraction cost;Many compounds can be extracted, regardless of their polarity, because ultrasonic extraction can be done with any solvent.SFE can only be extracted with CO2, so it is only suitable for extraction of non-polar substances.Ultrasonic extraction is better than microwave-assisted extraction reflected in: (1) in some cases, faster than microwave-assisted extraction;(2) in acid digestion, ultrasonic extraction is safer than conventional microwave-assisted extraction 3 in most cases, ultrasonic extraction steps are less, extraction process is simple, not easy to cause pollution to the extraction.For ultrasonic extraction, the soaking time, ultrasonic intensity, ultrasonic frequency and extraction time of samples before extraction are also important factors influencing the extraction rate of target components.