Alpha fourier transform infrared spectrophotometer

All chemicals were of analytical grade, purchased from Sigma-Aldrich and were used without further purification. All solvents used were of HPLC grade from Fisher Scientific. All aqueous solutions were prepared using distilled deionized water. ¹H and ¹³C NMR spectra were recorded on a Bruker Avance Neo 700 or a Bruker Avance 500 spectrometer. Mass spectra were run by the positive ion electrospray (ES) mode on an Agilent LC connected to an Agilent 6510 QTOF mass spectrometer or electron ionisation (EI) mode on a Thermo Finnigan MAT900xp mass spectrometer. IR spectra were recorded on a Bruker Alpha Fourier transform infrared spectrophotometer and were run neat. Melting points were recorded using a Stuart SMP30 melting point apparatus and were uncorrected. Absorption and fluorescence measurements of aqueous solutions containing fluorophores were carried out on a PerkinElmer Lambda 35 spectrophotometer and a Horiba Jobin Yvon Fluoromax-4 spectrofluorometer system with FluorEssence^TM as the driving software, respectively. Refractive indices were measured on an Abbe refractometer. Quantum yields of fluorescence were determined using quinine sulfate as the standard (Φ = 0.55) [26 (link),27 (link)].

Optical rotations were measured on a JASCO P-2000 polarimeter (JASCO, Easton, MD, USA). IR data was collected using a Bruker Alpha Fourier transform infrared spectrophotometer (Bruker, Billerica, MA, USA). NMR spectra were measured at ¹H resonance frequency on a Jeol Eclipse + 400 MHz spectrometer (JEOL, Peabody, MA, USA). Chemical shifts were calibrated internally to the residual signal of deuterated chloroform (CDCl₃ δ_H 7.26, δ_C 77.0). For NMR measurements concentration used was in the range of 3–8 mg of compound (depending on the amount of compound available) dissolved in 600 μL of deuterated chloroform. High-resolution mass spectra were obtained on a Bruker micrOTOF-Q III (Bruker Daltonics, Billerica, MA, USA). HPLC separations were performed using an Agilent 1200 HPLC system equipped with a quaternary pump, a diode array detector (Agilent, Santa Clara, CA, USA) and a normal phase silica gel column (Phenomenex Sphereclone^®, 4.6 mm × 100 mm, 5 µm). Reverse phase solid phase extraction (SPE) separation was carried out using SUPELCO Supelclean™ LC-18 (C-18, octadecyl) solid-phase extraction cartridges (Supelco^® Analytical, Bellefonte, PA, USA).

A sample of hot water soluble pectin and citric acid soluble pectin was analysed for main functional groups using Bruker Alpha Fourier transform infrared spectrophotometer (Germany) operating on Platinum-ATR to obtain FTIR spectra at 400–4000 cm⁻¹. Specimens of hot water soluble and citric acid soluble pectin were prepared for NMR analysis using a Varian 500 NMR spectrometer (USA). The ¹³C NMR spectra of the hot water soluble pectin and citric acid soluble pectin extracts in D₂O were obtained at 25°C and 50°C, respectively. Chemical shifts were expressed in δ (ppm) relative to acetone for hot water soluble pectin (δ 30.16) and citric acid soluble pectin (δ 29.65). The results were analysed by MestReNova NMR. In the elemental analysis, pellets of hot water soluble pectin were prepared and irradiated with an energy dispersive X-ray fluorescence spectrometer (Spectro X-Lab 2000, Kleve, Germany). Peaks shown by the spectrometer indicated the presence of particular elements, while the area under the peaks was an indication of the quantity of elements present.