Investigating natural rubber composition with Fourier Transform Infrared (FT-IR) spectroscopy: A rapid and non-destructive method to determine both protein and lipid contents simultaneously

Characterisation of macrogel composition from industrial natural rubber samples: Influence of proteins on the macrogel crosslink density

“…The speeds of the front and back rolls were 27.5 and 38.5 rpm, respectively. FT-IR spectra were recorded on these rubber sheets with OPUS 7.0 software on a Bruker Tensor27 spectrometer (Paris, France), using the Attenuated Total Reflection (ATR) mode, in the range of 4000-400 cm -1 with a resolution of 2 cm -1 [17]. The background was measured before testing each sample.…”

“…A mean spectrum was then calculated from the initial five spectra. Normalization of the FT-IR spectra was performed using the maximum absorbance of the =C-H out-of-plane bending band (840 cm -1 ), corresponding to the isoprene monomer, as previously described [17].…”

“…Nitrogen titration is usually performed to assess the protein content of NR samples [17,34]. The Dumas method was used to determine nitrogen contents.…”

“…About 600 mg of each homogenized sample was Figure 2. Diagram of the processing conditions used to prepare TSR10, TSR10CV and TSR3CV grades (reprinted from [17], by courtesy of Elsevier) calcined at 1100°C under oxygen flow. Combustion gases were trapped in order to separate nitrogen oxides from dust, water vapour, halogen compounds and carbon oxides.…”

“…This gel phase is composed of an insoluble fraction called 'macrogel' [11,12], and of microaggregates dispersed in the soluble fraction, called 'microgel' [13,14] (Figure 1). Some non-isoprene compounds of NR, such as lipids (1.5-4% w/w) [4,[15][16][17], proteins (1-3.5% w/w) [4,[17][18][19], and minerals (0.2% w/w) [4,20], are assumed to be responsible for the existence of this gel phase. For example, macrogel can be eliminated by transesterification or deproteinization of NR.…”