Qualitative analysis of black stone and its application for detecting Ag and Pb in liquid sample by laser-induced breakdown spectroscopy (LIBS)

The aim of this research is to characterize black stone and also to know the capability to adsorb Ag and Pb elements in solution. All analysis in this research used laser-induced breakdown spectroscopy (commercial LIBS) method with laser energy of 120 mJ, accumulation 4, gate delay 1 µs and air surrounding gas at 1 atmosphere. Before soaked in 20 ml solution containing Ag and Pb of 40 ppm in 1 hour, the stone was analyzed by LIBS and it contains the main elements such as Ca, Mn, Si, K, Fe, Mg, Mo, H, O and Na until 16 laser shots. However, after immersed in solution, the stone contains impurities Ag and Pb elements with signal to noise ratio (SNR) of 9.5 and 1.2 respectively. Based on this data, the stone is predicted to be able to adsorb Ag element in solution till 12.7 ppm. The data also show that Ag element was adsorbed homogenously by stone till 16th laser shots, although it was washed with flowing demineralized water before it was analyzed.