Determination of the content of Eucommia ulmoides gum by Variable Temperature Fourier Transform Infrared Spectrum

Abstract

Considering the rapidity and lesser sample amount required, the Fourier Transform Infrared Spectra (FTIR) was often used to quantitatively determine the rubber content of Russian dandelion, guayule, etc. This is because their chemical structure are cis-1,4-polyisoprene (CPI) which has a unique and isolate skeleton stretching vibration peak at 835 cm−1 band, and is convenient for determining the rubber content. However, this method is not suitable for Eucommia Ulmoides (EU) gum which will crystallize easily at room temperature due to the regular chemical structure of trans-1,4-polyisoprene (TPI), that will restrict the skeleton stretching vibration of TPI greatly. As a result, its FTIR spectrum only shows a very small peak at 845 cm−1 band hiding among a number of crystalline peaks around nearby, thus it cannot be used to determine the rubber content of Eucommia ulmoides oliv (E. ulmoids) directly. Actually, these crystalline peaks could be eliminated easily by elevating the temperature over 60 °C, and a unique and isolate skeleton stretching vibration characteristic band at 845 cm−1 was left alone in the TPI's FTIR spectrum which can be used expediently to determine the content of EU gum. At the present paper, the Variable Temperature Fourier Transform Infrared Spectroscopy (VTFTIR) was used to determine the rubber content of E. ulmoides. The results indicate that the rubber content of E. ulmoides samples (1–40, 5–35, 22–11) provided by Northwest Agriculture and Forestry University (NAFU) are 4.66%, 4.04%, 4.32% respectively, and the errors of average value were less than 5% compared with Soxhlet Extraction.