Studies of flame and plasma torch emission for simultaneous multi-element analysis—I: Preliminary investigations

Abstract

The need for rapid and relatively simple techniques for simultaneous multi-element analysis of solutions focusses attention on emission techniques using a high-temperature flame, a radio-frequency plasma torch or a plasma jet. This paper deals with the premixed nitrous oxide-acetylene flame and the inductively-coupled argon plasma torch as excitation sources for trace analysis of solutions. Experimental facilities encompass various commercially available burners (including a burner for a gas-shielded flame), an improved plasma torch using a new type of HF generator (52 MHz, 2 kW) and a new arrangement of an ultrasonic nebulizer, less conventional accessory optics, a medium monochromator (1-m Czemy-Turner), and a double-beam, dual-channel arrangement using two monochromators. Detection limits of representative elements were determined in both sources and the conditions favourable for simultaneous multi-element trace analysis were investigated. In many instances, detection limits lower than those published previously were attained. With the plasma torch, the ng ml region—and for many elements even the sub- ng ml region—is easily accessible. The paper includes a discussion of some fundamentals of detection limits. This is to connect the present approach, which stems basically from emission spectrographic analysis, more smoothly with common usage in flame spectrometrio analysis.