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Simultaneous Total and Speciation Analysis of Volatile Arsenic Compounds in Gas and Liquefied Gas Samples using GC-ICP-MS

This application note describes a novel gas sampling system that enables simultaneous GC-ICP-MS analysis of total and speciated volatile arsenic compounds such as arsine in gas and liquefied gas samples.

Volatile metal(loid) elements and compounds are present in many different types of gas and liquefied gas samples, such as natural gas and biogas. Arsenic (As) is one of the most prevalent elemental impurities in such samples, and it is of interest in many industries, including gas exploitation and processing, and polymer manufacturing. In addition to its potential toxicity and effect as an environmental contaminant, As must be carefully monitored and controlled in the petrochemical and polymer industries. Its presence in monomer gases such as ethylene and
propylene affects the properties of polymers synthesized from these gases. Volatile forms of As are also highly active catalyst poisons. Importantly, the toxicity of As depends on the chemical species, with arsine being the most toxic form. Reliable analytical methods are required, therefore, for both total and speciation analysis of
As compounds in gaseous samples.

Gas chromatography (GC) coupled with a mass spectrometer based detector provides a powerful solution for As speciation analysis. However, such systems are not always suitable for total As determination in gas samples, because species that do not elute from the column (i.e. associated with particulate matter) cannot be detected.

In this study, a novel GC-ICP-MS method was used that combines As speciation analysis and total elemental As determination in one measurement. The potential of the method for the simultaneous determination of total elemental concentrations and individual species of other elements, such as Hg, in gases is also shown.