Adding negatively charged reagent ions to SIFT-MS has opened up the analysis of many more inorganic gases in real time.


Murray Mcewan Syft Technologies CTO

Dr. Murray McEwan

FRSNZ, MSc(Hons), PhD


CTO

Murray was Professor of Chemistry at the University of Canterbury in Christchurch until 2010. His research interests were centred on selected ion flow tube mass spectrometry (SIFT-MS) and he developed strong research links with colleagues at the Jet Propulsion Laboratory in Pasadena, CA, USA investigating ion molecule chemistry of interstellar and planetary atmospheres.

When the University of Canterbury commercialized the technology with the formation of Syft Technologies Ltd in 2002, Murray served as Chief Technology Officer of the new company.

Since then he has been heavily involved with the transformation of the large laboratory based instrument into the small, sophisticated Voice instruments that are available today. He has continued with ion-molecule chemistry, method development, environmental applications and negative reagent ions.

HCl is a gaseous pollutant used in and produced from a wide range of industrial processes. But HCl is traditionally difficult to analyze because it is highly reactive and very soluble in water. The addition of negatively charged reagent ions to SIFT-MS has opened up the analysis of many more inorganic gases – such as Hydrogen Chloride (HCl) – in real time. 

With an established pedigree in volatile organic compound (VOC) analysis, Selected Ion Flow Tube Mass Spectrometry (SIFT-MS) has more recently been applied to direct analysis of inorganic gases such as HCl.

The SIFT-MS technique utilizes known ion-molecule reactions of well characterized reagent ions that have been mass selected. These ions are introduced into a flow tube and are carried down the flow tube in a stream of helium or nitrogen carrier gas. The sample for analysis is simply sucked into the flow tube at a known flow rate and the product of the reagent ion-analyte reaction monitored in real time by a mass spectrometer at the downstream end of the flow tube.

Traditionally the reagent ions used in SIFT-MS were H3O+, NO+ and O2+ generated from a microwave discharge of moist air. Recently the suite of reagent ions has been extended by five negatively charged ions, O, OH, O2, NO2 and NO3.

Four of the negatively charged reagent ions; O, OH, O2, and NO2, all react rapidly with HCl, forming the Cl ion as the product at m/z = 35 and 37 for 35Cl and 37Cl isotopes, respectively.  The concentration of HCl is simply defined by the ratio of Cl product ion counts to the reagent ion counts.  Analysis is direct – no pre-concentration, sample preparation, or chromatographic separation is required.

An example of SIFT-MS performance is shown in the follow graph, where the measured HCl concentration versus concentration diluted from a certified mixture was analyzed using NO2.

 

Hydrogen Chloride measured concentration (SIFT-MS) vs standard concentration

To learn more about the unique opportunities that SIFT-MS offers for rapid, simple analysis of HCl and other inorganic gases.

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