Enantioseparation by Sonochromatography

Comparison between the use of polyether ether ketone and stainless steel columns for ultrasonic-assisted extraction under various ultrasonic conditions

“…The ultrasound radiation, rather than temperature, has a dominant effect on reducing or enhancing the retention time depending on the larger, less-solvated ions or smaller, more-solvated ions, respectively [23] . However, in our previous studies on ultrasound-assisted chiral chromatography [25] , [26] , [27] , the SS column under the ultrasound output power of 135 W at different temperatures (10, 20, 25, 30, 40, 45, 50, and 60 °C) demonstrated small differences in extraction efficiency between the sonic and non-sonic conditions. Under ultrasound radiation, the elution time decreased at all temperatures and the enantioselectivity was improved at higher temperatures (45, 50, and 60 °C) [25] , [26] .…”

“…However, in our previous studies on ultrasound-assisted chiral chromatography [25] , [26] , [27] , the SS column under the ultrasound output power of 135 W at different temperatures (10, 20, 25, 30, 40, 45, 50, and 60 °C) demonstrated small differences in extraction efficiency between the sonic and non-sonic conditions. Under ultrasound radiation, the elution time decreased at all temperatures and the enantioselectivity was improved at higher temperatures (45, 50, and 60 °C) [25] , [26] . Previous study on ultrasound-assisted chiral separation utilized the ultrasound reduction technique at a high temperature, in which the elution of the first peak was accelerated with the ultrasound, and then the elution of the second peak was unaltered by removing the ultrasound [27] .…”

“…The addition of temperature as an experimental variable noticeably enhanced the UAE efficiency of the SS column. Based on the minimal ultrasound effect on the SS column observed in prior studies [25] , [26] , [27] , the enhanced extraction effectiveness of the SS column can be explained by the increased interaction between the sample and the stationary phase resulting from the conversion of ultrasound energy to heat. Furthermore, greater temperature increase was observed with higher ultrasound intensities for both initial temperatures (30 °C and 40 °C).…”

“…In the field of chromatography, ultrasound [22] , [23] , [24] , [25] , [26] , [27] and other external fields such as magnetic, optical, electric, and temperature [28] , [29] , [30] , [31] , [32] , [33] , [34] , [35] , [36] , [37] , [38] , [39] , [40] are used to manipulate chromatographic retention to optimize chromatographic separation and selectivity. For example, Cheng et al [22] applied 20 kHz ultrasound frequency to agitate strong acidic and basic resins and observed an increase in ion-exchange rate.…”

“…Oszwaldowski and Okada [24] tested polytetrafluoroethylene (PTFE) separation column in the ultrasonic bath at 35 kHz frequency and concluded ultrasound as an effective external factor which can control chromatographic retention and ionic interactions. Furthermore, our previous studies have introduced the idea of employing 25 kHz and 42 kHz ultrasound frequencies onto the SS column for chiral separation and demonstrated that ultrasound coupled with varying temperatures improved enantioselectivity and chiral separation efficacy while reducing the analysis time [25] , [26] , [27] .…”