Electrothermal vaporization inductively coupled plasma mass spectrometry: Fundamental studies and practical applications

Electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICPMS) is an elemental analysis technique that combines the ionization and detection limit capabilities of the ICPMS with the versatility of the graphite furnace ETV. Combined together almost every type of sample imaginable can be introduced into the ICP and detected including solids directly, solutions containing organic matrices, high dissolved solids and surfactants, and viscous samples such as petroleum and its byproducts. Furthermore, using ETV sample introduction allows for finite sample volumes in the range of 5--50 muL to be used.;One problem facing ETV-ICPMS is the inconsistency in analyte transport out the ETV that has been noted when samples and standards are not matrix matched. The transport efficiency for two different ETV systems was determined using an in-line electrostatic trap that allowed for continuous monitoring of the ETV carrier gas. Also investigated was the role that "carriers" play in increasing analyte transport out of the ETV.;A second problem with ETV-ICPMS is the incompatibility between the 1--3 s transient signals produced by the pulse heated ETV and the scanning quadrupole mass analyzer. Despite the recent introduction of time of flight mass analyzers with ICP sources, the majority of ICPMS systems continue to be sold with quadrupoles, making analysis using ETV sample introduction more complex. Two different methods to improve the compatibility between the ETV and the quadrupole were employed. The transient extension chamber or TEx chamber was presented as a means of exponentially diluting the ETV aerosol so that the signal would last on average 12--15 s rather than 1--3 s. Also presented was a method for the determination of the mum number of un-diluted transient signals that can be monitored simultaneously by a quadrupole mass analyzer.;Finally, the ability of the graphite furnace tube-type ETV to vaporize all types of sample matrices was tested by using it to introduce viscous samples of crude oil, maple syrup and Triton-X-100 (surfactant) into the ICPMS using a method described as the "frozen drop method". Using the frozen drop method viscous samples such as those mentioned above can be treated for a short time as a solid and manipulated with liquid nitrogen cooled tweezers. In this manner it is possible to introduce known amounts of sample directly, i.e., no dilution or sample preparation, into the ETV.