Laser Ablation and Low-Pressure Helium-ICP-MS for the Analysis of Alumina Powder Dispersed in Glycerol

Abstract

Because of the outstanding mechanical and thermal properties, alumina has been extensively used for the production of advanced ceramic materials. The physical and chemical properties of those ceramics are sensitive to trace impurities present in alumina; hence, the determination of impurities is indispensable for the quality control of the products. Although the Japanese Industrial Standard recommends to use acid pressure decomposition followed by inductively-coupled plasma-atomic emission spectrometry (ICP-AES), 1 the analytical method is accompanied by several problems, including a time-consuming procedure and inadequate sensitivity for trace elements.A combination of laser ablation (LA) and inductively-coupled plasma mass spectrometry (ICP-MS) offers a powerful and promising method for the analysis of solid samples. In LA/ICP-MS, a laser beam is irradiated on the surface of the sample and the resulting tiny particles are immediately analyzed by ICP-MS. The method is simple and rapid, and it has been used for the analysis of a wide range of solid samples, including rocks, metals, glasses, and ceramics. [2][3][4] The conventional argon ICP, however, causes serious spectral interferences originating mainly from argon and ambient air constituents (e.g., carbon, nitrogen, oxygen). 5 On the other hand, ICP-MS using a helium plasma generated under the evacuated conditions can overcome the abovementioned problems.7-10 By combining with laser ablation, lowpressure helium-ICP-MS became more useful for the rapid analyses of solid samples. 11,12 The combined method, however, requires standard reference materials (i.e., matrix-matched solid standards), which are often unobtainable commercially.In the present work, we tried to use glycerol solutions containing desired trace elements for preparing calibration curves. The proposed method was successfully applied to the multielement determination of impurities in powdered alumina samples. ExperimentalApparatus Details of the LA/low-pressure helium-ICP-MS employed in this experiment have been described previously. 12 The plasma torch was cooled by running water, and the interface between ICP and MS was made of aluminum to minimize the background spectra. 9 A Nd/YAG laser (1064 nm, SL402, Spectron Laser Systems) was used for the ablation of samples. The ablation cell was composed of a vacuum long flange (NW40, BOC Edwards), a glass cover (for the transmission of a laser beam) and two sidetubes (for in and out of the carrier gas, copper, 4 mm i.d.). To the bottom of the cell were attached an NW40 blanking flange and a centering O-ring (BOC Edwards) for replacing the samples.The flow rate of the carrier and outer gas was regulated by a mass flow controller (MFC-260E, Nippon AERA). The connection of the helium gas line was completed by using vacuum fitting joints (Ultra-Torr, Swagelok). The operating conditions are summarized in Table 1. ReagentsA standard indium solution (20 mg ml -1 ) was prepared by dissolving 1.0 g of indium metal (flake, Katayama Chemicals) in 15 ml of 14 M...