A model for calculating dead time and mass discrimination correction factors from inductively coupled plasma mass spectrometry calibration curves

Abstract

A model allowing simultaneous determination of the detector dead time and the mass discrimination factor in inductively coupled plasma mass spectrometry (ICP-MS), as well as the corresponding uncertainties, is presented and compared for three representative isotope systems, namely magnesium, indium and thallium. The advantages of using the model presented are ®rstly that both the detector dead time and the mass discrimination factor can be obtained simultaneously and secondly that the sampling time can be spent entirely on the isotopes of interest.

The importance of a correct dead time setting in isotope ratio mass spectrometry: Implementation of an electronically determined dead time to reduce measurement uncertainty

“…The ratio determined dead times were evaluated using two methods reported by Appelblad and Baxter [4] and Ramebäck et al [5]. In principal, both methods are based on regression analysis for the determination of τ.…”

“…Thus, the amplifier could then be configured to different artificial dead time settings of about 10, 20 and 70 ns. Dead time measurements with the ratio method were evaluated both according to Appelblad and Baxter [4] and Ramebäck et al [5]. Throughout this study, the "raw data" or "channel data" that can be obtained from the instrument software were used, and evaluations of these data were performed manually.…”

“…Ratio method according to [4] . Observe that the uncertainty in the dead time is expressed for k = 1, whereas k = 2 is applied to the uncertainty of the isotope abundance ratio.…”

“…By observing the change in signal ratio upon an intensity change, the dead time of the detection system can be determined. Several different approaches for evaluating the dead time based on isotope ratio measurements have been reported [2][3][4][5][6]. However, one limitation of this method is the precision with which the dead time can be determined.…”

“…However, one limitation of this method is the precision with which the dead time can be determined. Nelms et al [6] reported uncertainties in the range of 4-20 ns (k = 1) for different methods, and Appelblad and Baxter [4] reported uncertainties down to about 1 ns (k = 1) at best. If the dead time instead is determined via electronic measurement [5], the precision is mainly governed by the sampling rate of the measuring device.…”