Examinations for Sensitivity Improvement and Applications to Steel Samples of Mistral Desolvating Sample Introduction Method Hyphenated to ICP-MS/AES

Abstract

Synopsis : Mistral Desolvation (MD), a sample introduction method for Inductively Coupled Plasma (ICP)-Atomic Emission Spectroscopy (AES) and Mass Spectrometry (MS), provides sensitivity enhancement over 5 times compared to conventional sample introduction method (concentric nebulizer and Spray chamber). Some groups have been proposed different mechanisms of sensitivity enhancement by MD, e.g. inhibition of poly-atomic ion generation derived from solvent, influence of the change of plasma condition, and improvement of sample transportation efficiency in plasma. However, uniform understanding has not been obtained. In this paper, we have identified the dominant factor of a sensitivity enhancement by MD and examined application to chemical analysis of steel samples. It is found that the MD method provides decrease of 100-250 K plasma temperature, which leads to sensitivity loss. On the other hand, sample transportation efficiency improves by a factor of 4.7 times by virtue of an increase in the sum of small droplets less than 1.0 μm, which is comparable to fivefold sensitivity enhancement. Thus, we concluded that the dominant factor of sensitivity enhancement achieved by the MD method is improvement of sample transportation efficiency with decreasing droplet size. Besides, the standard steel samples have analyzed by MD-ICP-AES. It is found that almost tenth amount of sample consumption and almost 3-fold sensitivity can be achieved, the analyzed value corresponds exactly to certificated value. Therefore, this method can be expected to apply to chemical analysis of micro-alloy in steels.