Comparison of a direct injection nebulizer and a micronebulizer associated with a spray chamber for the determination of iodine in the form of volatile CH3I by inductively coupled plasma sector field mass spectrometry

Abstract

Experiments were performed to study the influence of the volatility of a liquid sample on various sample introduction systems. The test element was iodine using NaI as a non-volatile species and CH₃I as a volatile species. A direct injection nebulizer such as the DIHEN was compared to a micronebulizer associated with a cyclonic spray chamber. An ICP-MS was used for detection. A factor, K, was defined as the ratio of the ¹²⁷I signal obtained for CH₃I to that obtained for NaI. K values in the range 4–6 were obtained for a micronebulizer and a conventional nebulizer with spray chambers. Simple experiments showed that most of the explanation was related to evaporation of the aerosol in the spray chamber. When using a DIHEN, the K value was in the range 0.6–0.8, i.e., lower than unity, which would be the value if the DIHEN had fully eliminated the influence of the spray chamber. The departure from unity could not be explained by a change in the plasma characteristics and did not depend on the operating parameters, such as the carrier gas flow rate, the position of the nebulizer tip, or the spatial distribution of the sample.