Spectral analysis of astragalus based on laser-induced breakdown spectroscopy

As a classic Chinese medicinal herb with prominent clinical efficacy, Astragalus is widely used for disease prevention and health care, and its elemental composition and contents directly affect the quality and therapeutic effect of herbal materials. This work adopts laser-induced breakdown spectroscopy (LIBS) to carry out elemental analysis on 3-year-old Astragalus herb from Longxi, a representative authentic producing area in China. Key experimental parameters, including delay time, focusing position, laser pulse energy, and spectral accumulation times, were systematically optimized, and the optimal detection conditions were determined as 2.2 µs delay time, −2 mm, focusing position, 25 mJ laser energy, and 20 accumulations. Due to the complex organic matrix and the multi-elemental constituents of Astragalus, the LIBS spectra exhibit rich structural features, including single peaks, double peaks, overlapping peaks, and CN molecular bands. Through the analysis of complex spectral structure, the formation characteristics of different peak profiles were clarified, and characteristic lines applicable for herbal elemental analysis were screened out. Finally, more than 70 atomic and ionic lines corresponding to 11 elements (Mg, Ca, Al, Fe, Na, Ti, Sr, C, Si, K, Mn, etc.) were identified and compiled. This work provides important fundamental spectral data and technical support for qualitative or quantitative analysis of Astragalus.