Experimental Study on Terahertz Spectrum of Lacidipine

The terahertz time-domain reflection signals of highly pure Lacidipine (98%) and Lacidipine tablets (2%) were measured and then their absorption and refractive index spectra were extracted respectively. Through comparing the frequencies between the measured absorption peaks and the results calculated by CASTEP software, we got the fingerprint of Lacidipine using Lorentz fitting. There were six characteristic frequencies located at 0. 62, 0. 78, 1. 07, 1. 28, 1. 63 and 1. 76 THz, respectively. Because other substances were added into tablets as supplementary materials, and the recognition of absorption characteristics of lacidipine was disturbed by absorption of these substances, the number of characteristic absorption peaks decreased to 4 at 0. 62, 0. 78, 1. 28 and 1. 63 THz. In addition, there was a large difference in the refractive index spectra of the pure samples and oral tablets, which was also related to the supplementary materials in the oral administration. Although Lacidipine's content was very low in the actual Lacidipine oral tablets, THz fingerprint spectrum could still recognize some characteristic frequencies. Therefore, the terahertz time-domain spectroscopy is an effective tool for detecting components of Lacidipine drugs.