Avance digital 400 mhz nmr spectrometer

For the spectroscopic studies, NCL and EPO in different weight ratios (% w/w NCL: EPO = 1:10, 2:10, 3:10, and 4:10) were weighed and transferred to a scintillation vial. The mixture was dissolved in acetone to obtain a uniform solution. Acetone was evaporated using a rotary evaporator (Scilogex, Rocky Hill, CT) to obtain a solid dispersion of NCL and EPO. The solid dispersion was further dried overnight using a vacuum oven (Fisher Scientific, Waltham, MA). The NCL-EPO solid dispersions, EPO, and NCL were evaluated using the FTIR spectrometer (Nicolet iS10, Thermo Scientific, Waltham, MA) equipped with a diamond attenuated total reflection unit. The FTIR spectra were obtained in the transmission mode from 4,000 to 500 cm⁻¹. The 1H NMR spectra of NCL-EPO solid dispersions, EPO, and NCL were obtained using a Bruker Avance Digital 400 MHz NMR spectrometer (Bruker, Billerica, MA) coupled to a BACS 1 automatic sample changer. The spectrometer is equipped with a 5-mm PABBO BB- 1H/D Z-GRD probe. The spectra of the samples were recorded in (400 μl) deuterated chloroform (CDCl₃, Acros Organics, 99.5% D, Waltham, MA) with an average of 16 scans. The chemical shifts were reported in ppm using residual deuterated solvent peaks as an internal reference for 1H NMR: CDCl₃ (7.26 ppm).

Upon the completion of the reaction, the lipase PS IM was filtered off and the solvent was concentrated under vacuum. The residue was then purified by flash column chromatography using ethyl acetate/petroleum ether (boiling poin: 60–90°C) as an eluant. The structures of gastrodin ester derivatives were determined by NMR (Bruker AVANCE Digital 400 MHz NMR spectrometer, Germany) and mass spectra (Bruker maXis impact, Bruker Co., Germany) using ESI mode. The position of acylation in enzymatically prepared ester was determined by ¹³C NMR (100 MHz) and ¹H NMR (400 MHz).