Nicolet nexus 6700 spectrometer

The infrared spectra of clove and spearmint EOs, major EO compounds and raw matrices were characterized using a FTIR Nicolet Nexus 6700 spectrometer (Thermo Scientific, Courtaboeuf, France) in attenuated total reflection mode, equipped with a Mercury-Cadmium-Telluride High D detector and using the Omnic v7.3 software (Thermo electron). The spectra of major compounds of both EOs were obtained by deposing around 13 mg of the standard components over the diamond crystal (Ø = 2 mm) of a Smart DuraSamplIR accessory (Thermo Scientific, U.K.). Spectral data were collected at room temperature and accumulated from 64 scans with a resolution of 2 cm^-1 in the range of 800 to 4000 cm^-1. A correction was applied by subtracting the background spectrum of air. The matrices with a known amount of EO were grinded using a laboratory mortar until a fine powder was reached. Then, the powder was directly analyzed by the ATR-FTIR using the same procedure described above. The crystal was cleaned between measurements with ethanol and dried with a lint-free tissue. For each sample, three or four spectral data were performed. Then, for the calibration curve of clove EO produced from 9 concentrations by triplicate, 108 (N = 4 x 9 x 3) spectral data were acquired. For spearmint EO, 54 (N = 3 x 6 x 3) spectral data were taken.

The synthesis of SPI-CH was confirmed by nuclear resonance (¹H NMR, JEOL ECS, Tokyo, Japan, 400 MHz) spectra and UV-Vis spectrophotometry (TU-1901, Purkinje General Instrument Co., Ltd., Beijing, China). The HCA, SPI, and SPI-CH samples were dried and dissolved into DMSO-d₆. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectra of SPI-CH conjugates was recorded using a Nicolet Nexus 6700 spectrometer (Thermo Scientific, Madison, WI, USA) from 4000 to 650 cm⁻¹ wavenumbers with 32 scans.