The ultrasound radiation is provided by either ultrasonic bath or ultrasonic probe in most laboratory environments. The key factors that contribute to the extraction yield in ultrasonic bath systems include but not limited to power, extraction time, ultrasound frequency, bath water temperature, solvent (composition and pH), sample position (vertical or horizontal) in the vessel, type of extraction vessel, etc. Therefore, it has attracted considerable research interest and has been widely applied in various fields including food processing, cleaning, sonochemistry, plastic welding, and medical applications, in laboratory and industrial settings.Ĭurrently, ultrasound-assisted extraction (UAE) is widely used to obtain natural components from plants such as ginseng saponins from ginseng roots, phenolic compounds from wheat bran, essential oil from garlic, polyphenols from black chokeberry, oil from flaxseed, and lycopene from tomato. Among many novel techniques, the ultrasound emerged with its advantages as a rapid, low-cost, non-thermal, environmentally friendly, and easy-to-operate method. Ultrasound is the sound waves with frequencies beyond the human audible range (>20 kHz) and categorized into three frequency ranges: low frequencies (20 kHz – 100 kHz), high frequencies (100 kHz – 1 MHz), and diagnostic ultrasound (1 MHz – 500 MHz). The findings of this study contribute to elucidating the roles of column materials in UAE and UAC.
In contrast, at lower frequencies of 40 kHz and 25 kHz, no significant differences in the acoustic effects were observed between the PEEK and SS materials. Unlike the SS material, the PEEK material was more affected by temperature and acoustic effects under identical conditions, especially at 132 kHz ultrasound frequency. The most optimal ultrasound frequencies, in terms of enhancing extraction effectiveness, are in the order of 132 kHz, 40 kHz, and 25 kHz. At a maximum power density of 45 W/L, the extraction effectiveness ratio of PEEK to SS was in the range of 1.8 - 3.9 depending on the specific frequency, initial temperature, and with or without temperature control. The PEEK material was significantly affected by ultrasonic radiation compared to the SS material, especially at a higher temperature (40 ☌), power intensity (100 %), and frequency (132 kHz) with sweep mode.
After 30 min of extraction, the amount of extract was determined by HPLC. Empty SS and PEEK columns were used to extract dyes from a fabric under identical conditions with several parameters including the initial ultrasonic bath temperatures (30 ☌ and 40 ☌), ultrasound power intensities (0, 20, 40, 60, 80, and 100 %), ultrasound operation modes (normal and sweep), and ultrasound frequencies (25 kHz, 40 kHz, and 132 kHz) to compare their extraction capabilities. The ultrasound-assisted extraction (UAE) was conducted using the stainless steel (SS) and polyether ether ketone (PEEK) columns and analyzed with high-performance liquid chromatography (HPLC) to understand the mechanism of ultrasound-assisted chromatography (UAC).
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