Design and performance of an atmospheric pressure sampling interface for ion-trap/time-of-flight mass spectrometry

Abstract

An ion-trap/time-of-flight mass spectrometer in combination with an atmospheric pressure sampling interface was developed in order to simultaneously profit from the ease of sample handling at ambient pressure, from the storage and accumulation capabilities of an ion trap, and from the acquisition speed and sensitivity of a time-of-flight mass spectrometer. The sampling interface is an intermediate-pressure vacuum manifold that serves to enrich sampled analytes by jet separation with respect to the carrier gas ͑air͒ and simultaneously maintain vacuum conditions inside the ion-trap/ time-of-flight instrument. Neutral analyte molecules are sampled and later ionized either by electron impact or chemical ionization. Ion accumulation is performed with a rf-only quadrupole ion trap with ground potential on the end caps during storage. For mass analysis, the trap's electrodes serve as a pulsed ion source for the attached linear time-of-flight mass spectrometer. In addition, laser desorbed molecules can also be sampled with this kind of instrument. Successful operation is shown by analyzing volatile substances ͑aniline, bromobenzene, styrene, and perfluorotributylamine͒, as well as laser-desorbed organic solids. Figures of merit include a sensitivity of 10 ppm, resolving power of 300 and demonstration of a mass spectrum of laser-desorbed anthracene with a signal-to-noise ratio of 270.

Methods for Molecular Nanoanalysis

“…To overcome previous instrumental limitations, we have developed in the meantime a SNOM-MS instrument with a highly sensitive ion trap time-of-flight (IT-TOF) mass analyzer built specially for this application [18]. A schematic is shown in Fig.…”

Characterization of aerosol plumes in nanosecond laser ablation of molecular solids at atmospheric pressure

“…In MALDI, only the ionized analyte species originating from the laser ablation and ionization process are monitored in a mass analyzer. Since in MALDI very low ion-to-neutral ratios between 10 −5 and 10 −3 are typical [8], our design of a mass spectrometer for high-resolution surface analysis is based on sampling neutral ablation products at atmospheric pressure, and guiding them into the ion source of a mass spectrometer by an interface [9].…”

Imaging techniques for elements and element species in plant science

“…16 The tapered probe can either be an aperture optical fiber as in scanning near-field optical microscopy (SNOM) or a metal needle. The former utilizes a sharpened metal-coated optical fiber to lead the illuminating light to pass through the very small aperture at the end of the fiber onto the sample surface with a spot much smaller than the diffraction limit (Bl/2), [129][130][131][132][133] while the latter makes use of a sharp metallic tip inserted in the radiation near-field to form the evanescent nearfield radiation. [134][135][136][137] With this technique, the resolution of images is only limited by the detector/probe dimension (usually from tens to hundreds of nanometres) and not by the wavelength of the illuminating light.…”

“…The tiny amount of the ablated materials was analyzed by a quadrupole mass spectrometer (QMS) with the assistance of a nanosampling interface using a heated stainless steel capillary orifice called ion-trap positioned very close (o5 mm) to the probe. 131 An aperture optical probe combined with a time-of-flight mass spectrometer (TOF-MS) via the ion-trap sampling interface was developed later by the same group 132 to analyze organic samples such as solid 2,5-dihydrobenzoic acid, anthracene and pyrene. 133 With such an arrangement, near-field laser ablation MS at atmospheric pressure with full mass spectral information was shown for the first time with a lateral resolution on the low-micrometre scale (B5 mm).…”