Multidimensional Separation of Natural Products Using Liquid Chromatography Coupled to Hadamard Transform Ion Mobility Mass Spectrometry

A high performance liquid chromatograph (HPLC)was interfaced to an atmospheric drift tube ion mobility time of flight mass spectrometry. The power of multidimensional separation was demonstrated using chili pepper extracts. The ambient pressure drift tube ion mobility provided high resolving powers up to 166 for the HPLC eluent. With implementation of Hadamard transform (HT), the duty cycle for the ion mobility drift tube was increased from less than 1% to 50%, and the ion transmission efficiency was improved by over 200 times compared with pulsed mode, improving signal to noise ratio 10 times. HT ion mobility and TOF mass spectrometry provide an additional dimension of separation for complex samples without increasing the analysis time compared with conventional HPLC.

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Uniform Moment Theory for Charged Particle Motion in Gases

Moment equations for the motion of trace amounts of charged particles through dilute gases are developed from the Boltzmann equation. A new method for truncating the coupled moment equations is used to develop differential equations governing the moments in successive approximations. The first approximation equations are shown to agree completely with equations known to describe ion motion in drift-tube mass spectrometers, ion mobility spectrometers, ion traps, and collision-dominated ion cyclotron resonance experiments. Applications to differential mobility spectrometers and other devices are also described.     

Comprehensive software suite for the operation, maintenance, and evaluation of an ion mobility spectrometer

Scientific applications of Ion Mobility Spectrometry require the ability to easily compare data between different laboratories. Reduced mobility values attempt to provide this functionality, but no standard exists for the collection and manipulation of the raw data obtained during an IMS experiment. We have created a comprehensive software suite based on the LabVIEW programming language that can be used to collect and interpret IMS data. The software may be used to collect data from a stand-alone IMS cell, a voltage sweep IMS cell, or a coupled chromatography-IMS system, and this framework may be adapted to incorporate mass spectral data analysis as well. This software is provided under an open source license for the benefit of the IMS community.     

High spin structure in127Xe and125Xe

Excited states of the nuclei¹²⁷Xe and¹²⁵Xe have been investigated in the inverse kinematic reactions⁴⁸ Ca(⁸² Se,(3.5)n) at 275 MeV beam energy with the OSIRIS multidetector system at the VICKSI-accelerator of the HMI Berlin. The level scheme of¹²⁷Xe was extended up to a level of tentative spin (51/2^?). Two excited bands of 3QP-character were observed. For¹²⁵Xe these structures were extended towards higher spins. Experimental Routhians of selected bands are presented.     

Ion mobility detection of polydimethylsilicone oligomers following supercritical fluid chromatographic separation

A mixture of polydimethylsilicones (Dow Corning 200), average molecular weight 2000 a.m.u., was separated by simultaneous density and temperature-programmed supercritical fluid chromatography and detected by ion mobility detection. Ion mobility spectra were captured by Fourier transform ion mobility spectrometry. Using information from these spectra it was possible to selectively detect a single compound in the complex mixture. A detector temperature investigation demonstrated that, for the efficient transfer of high-molecular-weight compounds from the column to the detector, the interface to the detector must be heated. Using a 50 microns I.D. column, a Guthrie-type restrictor and a detection temperature of 250 degrees C, as many as 70 oligomers were separated and detected.     

Measurement of strong interaction parameters in antiprotonic hydrogen and deuterium

In the PS207 experiment at CERN, X-rays from antiprotonic hydrogen and deuterium have been measured at low pressure. The strong interaction shift and the broadening of the K _α transition in antiprotonic hydrogen were determined. Evidence was found for the individual hyperfine components of the protonium ground state. This revised version was published online in August 2006 with corrections to the Cover Date.     

Fourier transform ion mobility spectrometry of barbiturates after capillary gas chromatography

This paper demonstrates a novel operating mode of an ion mobility detector (IMD) for obtaining both qualitative and quantitative data after capillary gas chromatographic separation of 5,5′-disubstituted barbiturates. Using a recently developed time dispersive Fourier transform method for ion mobility spectrometry, complete ion mobility spectra could be obtained for each component in the chromatogram. This type of spectra can be used for providing qualitative information on unknown compounds or for selecting the proper detector conditions needed when operating in the continuous mobility monitoring mode. In this study each of the five barbiturates investigated produced a Fourier transformed ion mobility spectrum containing one major product ion. When drift times corresponding to those of the product ions measured in the FT mode were monitored continuously, selective chromatographic detection of the barbiturates was achieved. In one case even isomers could be differentiated based on mobility characteristics.