Performance of ICP-TOF-MS for ultra-trace element analyses in ice cores

TL;DR

This study compares new and established methods for analyzing ultra-trace elements in ice cores, finding them equally effective.

Contribution

Demonstrates that ICP-TOF-MS performs as well as ICP-SF-MS for ultra-trace element analysis in ice cores.

Findings

ICP-TOF-MS showed excellent performance for trace elements in the mass range 23 to 238.

Precision and accuracy of ICP-TOF-MS were comparable to ICP-SF-MS for ultra-trace analysis.

Mass interference limited performance for 45Sc but not for other elements.

Abstract

Ice cores serve as unique paleo-archives allowing access to long-term records of trace elements, which are important for our understanding of global biogeochemical cycles and air pollution. However, analysis of trace elements in ice cores is a challenge, because of very low concentration levels and their presence in dissolved and particulate form. The commonly used and well-established technique for analysis of trace elements in ice cores is inductively coupled plasma sector field mass spectrometry (ICP-SF-MS). Recently, inductively coupled plasma time of flight mass spectrometry (ICP-TOF-MS) was introduced as a new, promising technique. Due to its fast acquisition time for the near-full mass spectral range, it allows for the detection of short transient signals, offering the opportunity to determine the elemental composition of single particles. In this study, the performance of this new technique for analyzing total trace element concentrations was tested and compared to the one established in the field of ice core research. The focus was on sensitivity, precision, and optimization of sample preparation in sections from two ice cores (Colle Gnifetti, Cerro Negro), characterized by different impurity levels. The performance of the ICP-TOF-MS was excellent for the investigated trace elements within the nominal mass range from 23 to 238, except for 45Sc because of insufficiently resolved mass interferences. This is very promising for many applications in ice core research, especially in view of the great benefit to analyze single particles simultaneously in the same sample.

Ice cores record trace elements of the past, key for studying biogeochemical cycles and pollution histories. For the challenging ultra-trace analysis, no significant difference in precision or accuracy were detected between ICP-TOF-MS and ICP-SF-MS.

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