Extending the capabilities of electrothermal vaporization-inductively coupled plasma mass spectrometry (ETV-ICPMS): Coupling the graphite furnace to a sector field instrument

Abstract

This paper reports on the capabilities of the combination of an electrothermal vaporization (ETV) unit and a state-of-art single-collector sector field inductively coupled plasma mass spectrometer (SF-ICPMS). The basic analytical characteristics of this set-up were evaluated and compared to those of the more traditional combination of ETV and quadrupole-based (Q) ICPMS instrumentation. ETV-SF-ICPMS seems capable of providing a superior performance in terms of sensitivity (15- to 20-fold improvement in low resolution mode) and, also in terms of selectivity, as in medium resolution mode significantly lower LODs were achieved, especially for some low-mass elements, for which the most abundant nuclide suffers from spectral overlap as a result of the occurrence of carbon-containing polyatomic ions (e.g., ⁵²Cr, ²⁸Si) at low mass resolution. No deterioration was established in terms of stability, linear dynamic range or tolerance to matrix effects in comparison with ETV-Q-ICPMS. Also the possibilities for multi-element monitoring were studied and shown to be similar (monitoring of up to approximately 20 nuclides during the same tube firing is feasible), owing to the enhanced scanning speed and reduced magnet settling time that current SF-ICPMS displays when compared to older SF instrumentation. It is demonstrated that this instrumentation still preserves the most relevant advantages of the ETV technique, such as i) the potential for temporal separation of overlapping isobaric signals (e.g., ¹⁰²Ru and ¹⁰²Pd; ¹⁹²Os and ¹⁹²Pt; ¹³⁰Te and ¹³⁰Ba) under optimum vaporization conditions, and ii) the ability to analyze solid samples directly, as shown by the determination of Cr and Si in biological reference materials. By operating the instrument at higher mass resolution (4000), interference-free conditions could be realized for several isotopes of the target elements and, thus, isotope dilution could be deployed for their quantification, enabling the matrix effects observed to be overcome.