Atomic Emission Spectrometry with a Skimmed Inductively Coupled AR Plasma

Abstract

A skimmer located below the usual observation height of an inductively coupled plasma (ICP) allows the axial channel region of the ICP to flow through the central hole of the skimmer while the outer Ar flow is deflected. Signal-to-background (S/B) ratios and the estimated detection limits measured immediately above the skimmer were generally 5 to 20 times superior to the best results obtained by the conventional ICP system. The highest S/B lines possessed wavelengths greater than 300 nm. Matrix effect studies on the Ca-PO4 and the Ca-Al systems revealed that the skimmed plasma was as free of vaporization-atomization interference as the conventional plasma, but easily ionizable elements produced a greater level of suppression/enhancement effects. Electron number densities, as determined via the series limit line merging technique, were lower in the skimmed plasmas as compared with the conventional ICP's.

Analytical performance of a low-gas-flow torch optimized for inductively coupled plasma atomic emission spectrometry

“…Other experimental conditions are Identified in column 5, Table II. that the magnitude of ionic signal depression observed in the low flow torch is comparable to the level reported for the conventional ICP (39,40). In the case of the Ca I line, however, the enhancement effect could be eliminated only when the low-flow torch was operated at a forward power and an outer gas flow of 1100 W and 7 L/min, respectively.…”

“…Matrix Effect Studies. For evaluation of this aspect of analytical performance, the matrix effects previoulsy investigated (39,40) were repeated with the low-flow ICP torch.…”

“…Figure 1 presents the interference response curves for the Ca-P04 system obtained with the low-flow torch. At an outer gas flow of 4 L/min, the low-flow torch was as free as the conventional torch from interference (39,40) when the P04/Ca molar ratio ranged between zero to 1000. As the outer gas flow was increased to 7 L/min in the low-flow torch, slight depressions in both Ca atom and ion line intensities were observed at higher phosphate concentration.…”

Elemental matrix effects in ICP-AES

“…However, the presence of EIEs modified the response in a more efficient way for the skimmer based plasma. 131…”