Study on the spectra of Tieguanyin tea and ash by laser-induced breakdown spectroscopy

Abstract

Tea ash is the inorganic residue of tea after a series of chemical and physical reactions under high temperature environment. The compositions of tea and ash are very different. In addition, the compositions of ash are closely related to the quality of tea. In this work, the compositions of Tieguanyin tea and ash were analyzed by laser-induced breakdown spectroscopy (LIBS), and the differences of elements in tea and ash were analyzed qualitatively. Tea contains the main elements, such as Ca, Na, Mg, and K, trace elements Fe, Cu, Zn, Mn and Sr, and other metallic elements Al, Li and Ba. Comparing the atomic and ionic lines in LIBS spectra of tea and ash, it was found that the spectral line intensities of metallic elements, i.e. Ca, Al, Mn, Mg, K, Na, Li, in the ash were significantly enhanced. In addition, there were CN, C2 and CaO molecular lines in the LIBS spectra of tea, but only CaO free radical was detected in the LIBS spectra of ash. The reason of the differences between the molecular lines of LIBS spectra of tea and ash was analyzed. This work is to determine the material compositions of tea and ash, which provides a basic foundation for the quality judgment of tea and a new idea for the enrichment detection of metallic elements.