Multi-element detection for supercritical fluid chromatography by inductively coupled plasma mass spectrometry

Abstract

The feasibility of multi-element detection using supercritical fluid chromatography (SFC) with inductively coupled plasma mass spectrometry (ICP-MS) has been investigated for organomercury and organolead compounds. Since a quadrupole mass spectrometer is a sequential instrument, multi-element detection of transient signals presents difficulties; therefore, detection is usually performed in a single-ion monitoring mode. The applicability of utilizing time-resolved acquisition (TRA) software for quantitative determinations using SFC was investigated and compared with results obtained for single-ion monitoring modes. Detection limits were found to be approximately 5–10 pg for diethylmercury (DIEM) using TRA detection and 3 pg using single-ion monitoring detection. The detection limits of tetrabutyllead (TTBL) and tributyllead (TRBL) acetate were found to be 0.7–3 and 50–100 pg, respectively, for the TRA acquisitions, and 0.5 and 10 pg for single-ion monitoring measurements. The calibration graphs were linear over three decades for DIEM and TTBL, and two decades for the TRBL. The precision of the technique was between 1 and 5% relative standard deviation for 5 ng injections of the compounds of interest. The accuracy of the SFC–ICP-MS single-ion monitoring technique was demonstrated by analysis of a National Institute of Standards and Technology (NIST) standard reference material (SRM) 2715 Lead in Reference Fuel, giving a concentration of 785 ± 9.71 ppm of tetraethyllead, with the SFC–ICP-MS system, compared with the certified value of 784 ± 4.00 ppm at the 95% confidence level.