非金属元素分析のためのヘリウム大気圧マイクロ波プラズマ発光分光分析法

Abstract

The accurate determination of trace elements in steel is an important and challenging task in analytical chemistry. The variation of the contents of nonmetal elements such as C, P and S in steel can have a significant influence on the mechanical and physical properties. A sensitive and accurate method for the determination of these elements in steels is therefore required.The aim of the present work is to develop an accurate method using He-MIP AES (Helium Microwave-Induced Plasma Atomic Emission Spectrometry) to determine the trace amounts of these elements in the gas, liquid and solid samples. The optimization of the He-MIP AES technique and its analytical figures of merit, as well as its application to the determination of these elements in the samples, were described. The samples were transported and excited in a microwave induced helium plasma operated at atmospheric pressure.A high-power (∼1000 watt CW, 2.45 GHz) annular-shaped microwave-induced helium plasma (He-MIP) was developed for the determination of nonmetals in the aqueous solutions, and the characteristics were presented. The plasma was generated at atmospheric pressure by an Okamoto cavity of the surface wave mode. No external cooling was used to stabilize the plasma. The electron density and iron-excitation temperature were on the order of 1014/cm3 and 6500K, respectively. An air for gas sample was aspirated with an aspirator and introduced directly into the He-MIP. Carbon (247.9 nm) in the air was detected. An aqueous solution was injected into the plasma by an ultrasonic system with desolvation and condensation. Introduction of aqueous fluoride in the form of NaF, chloride in the form of NaCl and bromide in the form of KBr produced intense emission and detection limits of 100 ppb for FI (685.6 nm), Cl II (479.5 nm) and 150 ppb for Br II (470.5 nm) were obtained. Detection limits of the carbon and phosphorous in the aqueous solution were 1 ppb and 2 ppb, respectively.