Nicolet 560 ft ir spectrometer

The culture broth was centrifuged and the resulting supernatant was used for purification of exopolysaccharide and PMA. These two biopolymers were purified by the repeated ethanol precipitation [19 (link)]. The first addition of 1 volume of cold ethanol to the supernatant was to selectively purify exopolysaccharide as precipitates, the precipitated exopolysaccharide was then subjected to dialysis for structure characteristics. After the removal of the exopolysaccharide, the supernatant was added with 2 volume of ethanol, the mixture was kept at 4 °C for overnight for precipitation of PMA.
The purified exopolysaccharide was characterized by Fourier transform infrared spectroscopy (FT-IR), ¹H and ¹³C nuclear magnetic resonance (NMR) spectra. FT-IR was performed on a Nicolet 560 FT-IR spectrometer (Thermo, USA) and the sample was blended with KBr pellet. The ¹H and ¹³C-NMR spectra were recorded using a Bruker AVANCE AV-400 spectrophotometer (Bruker Biospin Corp., Billerica, MA), 10 mg of the purified exopolysaccharide was dissolved in 0.5 mL DMSO-d₆ solvent and TMS was used as an internal standard for proton NMR [25 (link)].

A Thermo Nicolet 560 FTIR spectrometer (USA) was applied to monitor the FTIR spectra of the samples in the range of 4000–400 cm⁻¹. A small amount of fully dried sample to be tested and potassium bromide were ground evenly in a mortar, then placed on a tablet press and pressed into translucent flakes at a pressure of 10 Mpa. The flakes were tested in a Fourier infrared spectrometer.