Identification of authentic and adulterated Aquilariae Lignum Resinatum by Fourier transform infrared (FT-IR) spectroscopy and two-dimensional correlation analysis

• Standard and adulterated Aquilariae Lignum Resinatum are studied by FT-IR and 2D-IR.
• FT-IR shows that the adulterated samples contain little or different resin compounds.
• Differences between standard and adulterated samples are remarkable in 2D-IR spectra.
• FT-IR and 2D-IR can identify Aquilariae Lignum Resinatum simply and quickly.

As a kind of expensive perfume and valuable herb, the commercial Aquilariae Lignum Resinatum (ALR) is often adulterated for economic motivations. In this research, Fourier transform infrared (FT-IR) spectroscopy and two-dimensional (2D) correlation analysis are employed to establish a simple and quick identification method for the authentic and adulterated ALR. In the conventional infrared spectra, the standard ALR has a strong peak at 1658 cm−1 referring to the conjugated carbonyl of resin, while this peak is absent in the adulterated samples. The position, intensity, and shape of the auto-peaks and cross-peaks of the authentic and adulterated ALR are much different in the synchronous 2D correlation spectra with thermal perturbation. In the range of 1700–1500 cm−1, the standard ALR has four obvious auto-peaks, while the strongest one is at 1659 cm−1. The adulterated sample w-1 has three obvious auto-peaks and the strongest one is at 1647 cm−1. The adulterated sample w-2 has three obvious auto-peaks and the strongest one is at 1519 cm−1. The adulterated sample w-3 has four obvious auto-peaks and the strongest one is at 1690 cm−1. The above auto-peaks confirm that the standard ALR contains a certain content of resin compounds, while the three counterfeits contain little or different resins. The results show the potential of FT-IR spectroscopy and 2D correlation analysis in the simple and quick identification of authentic and adulterated ALR.

Figure: Synchronous 2D-IR spectra of authentic ALR (a) and adulterated samples (b-d)Figure optionsDownload as PowerPoint slide