Ion mobility-mass spectrometry (IM/MS) is becoming a valued tool in life science research. Pivotal to successful application of IMS-MS is a means of accurately relating the ion mobility spectrum to molecular structure. To this end, experimental collision cross sections are often obtained in nitrogen and compared to values predicted for molecular model structures in helium.Here, we discuss a recently developed parameter set for the projected superposition approximation (PSA) method to directly predict cross sections in N2. We discuss the effect of N2as a drift gas on molecular structure of biological macromolecules and examine the appropriateness of comparing experimental data obtained in nitrogen to theoretical cross sections predicted for helium.First, we present PSA parameters for a number of elements that were derived from temperature-dependent experimental collision cross sections determined with N2as a drift gas in a temperature range from approximately 80 to 500 K.We further discuss the relationship between cross sections determined in different drift gases by comparing the measured N2 cross sections to measurements obtained in He, again in the temperature ranging from approximately 80 to 500 K. Our data reveal that a simple relationship between the cross sections in He and N2 does not exist. Instead, molecular shape and other properties such as drift gas temperature appear to effect cross sections differently in He when compared to N2. We discuss the impact of our data on current protocols to elucidate molecular structure by IM/MS.Lastly, we present our recent efforts to make the PSA software available. To this end, we have created a web interface where access to the PSA software including all parameter sets is provided to the general public free of charge. We outline how this web-portal can be used in order to obtain PSA collision cross sections.

Projected superposition approximation: A novel parameter set for prediction of cross sections in nitrogen as a drift gas

248th National Meeting (2014)

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