Navigate flying molecular elephants safely to the ground: mass-selective soft landing up to the Mega-Dalton range by Electrospray Controlled Ion-Beam Deposition

The prototype of a highly versatile and efficient preparative mass spectrometry system used for the deposition of molecules in ultra-high vacuum (UHV) is presented, along with encouraging performance data obtained on four model species which are thermolabile or not sublimable. The test panel comprises two small organic compounds, a protein, and a large DNA species covering a 4-log mass range up to 1.7 MDa as part of a broad spectrum of analyte species evaluated to date. Three designs of innovative ion guides, a novel digital mass-selective quadrupole (dQMS) and a standard electrospray ionization (ESI) source are combined to an integrated device, abbreviated Electrospray Controlled Ion Beam Deposition (ES-CIBD). Full control is achieved by i) the square-wave-driven radiofrequency (RF) ion guides with steadily tunable frequencies, including a dQMS allowing for investigation, purification and deposition of a virtually unlimited m/z range, ii) the adjustable landing energy of ions down to ~2 eV/z enabling integrity-preserving soft-landing, iii) the deposition in UHV with high ion beam intensity (up to 3 nA) limiting contaminations and deposition time, and iv) direct coverage control via the deposited charge. The maximum resolution of R=650 and overall efficiency up to T_total=4.4% calculated from solution to UHV deposition are remarkable as well, while the latter is mainly limited by the not yet optimized ionization performance. In the setup presented, a scanning tunneling microscope (STM) is attached for in situ UHV investigation of the deponents demonstrating a selective, structure-preserving process and atomically clean layers.

Navigate flying molecular elephants safely to the ground: mass-selective soft landing up to the Mega-Dalton range by Electrospray Controlled Ion-Beam Deposition

The prototype of a highly versatile and efficient preparative mass spectrometry system used for the deposition of molecules in ultra-high vacuum (UHV) is presented along with encouraging performance data obtained on model species which are thermolabile or not sublimable. The test panel comprises two organic compounds, a protein, and DNA covering a 4-log mass range up to 1.7 MDa as part of a broad spectrum of analyte species. Three designs of innovative ion guides, a novel digital mass-selective quadrupole (dQMS) and a standard electrospray ionization (ESI) source are combined to an integrated device, abbreviated Electrospray Controlled Ion Beam Deposition (ES-CIBD). Full control is achieved by i) the square-wave-driven radiofrequency (RF) ion guides with steadily tunable frequencies, including a dQMS allowing for investigation, purification and deposition of a virtually unlimited m/z range, ii) the adjustable landing energy of ions down to ~2 eV/z enabling integrity-preserving soft-landing, iii) the deposition in UHV with high ion beam intensity (up to 3 nA) limiting contaminations and deposition time, and iv) direct coverage control via the deposited charge. The maximum resolution of R=650 and overall efficiency up to T-total=4.4% calculated from solution to UHV deposition are remarkable as well, while the latter is mainly limited by the not yet optimized ionization performance. In the setup presented, a scanning tunneling microscope (STM) is attached for in situ UHV investigation of the deponents demonstrating a selective, structure-preserving process and atomically clean layers.

Characterisation of the transfer of cluster ions through an atmospheric pressure interface time-of-flight mass spectrometer with hexapole ion guides

Here we present an alternative approach of an atmospheric pressure interface (APi) time-of-flight mass spectrometer for the study of atmospheric ions and cluster ions, the so-called ioniAPi-TOF. The novelty is the use of two hexapoles as ion guides within the APi. In our case, hexapoles can accept and transmit a broad mass range enabling the study of small precursor ions and heavy cluster ions at the same time. Weakly bound cluster ions can easily de-cluster during ion transfer depending on the voltages applied to the ion transfer optics. With the example system of H3O+(H2O)n=0-3, we estimate that cluster ions with higher binding energies than 17 kcal mol−1 can be transferred through the APi without significant fragmentation, which is considerably lower than about 25 kcal mol−1 estimated from the literature for APi-TOFs with quadrupole ion guides. In contrast to the low-fragmenting ion transfer, the hexapoles can be set to a high-fragmenting declustering mode for collision-induced dissociation (CID) experiments as well. The ion transmission efficiency over a broad mass range was determined to be on the order of 1 %, which is comparable to existing instrumentation. From measurements under well-controlled conditions during the CLOUD experiment, we demonstrate the instrument's performance and present results from an inter-comparison with a quadrupole-based APi-TOF.

Characterisation of the transfer of cluster ions through an Atmospheric Pressure interface Time-of-Flight mass spectrometer with hexapole ion guides

Here we present an alternative approach of an Atmospheric-Pressure interface (APi) Time-Of-Flight mass spectrometer for the study of atmospheric ions and cluster ions, the so-called ioniAPi-TOF. The novelty is the use of two hexapoles as ion guides within the APi. As we will show, hexapoles can accept and transmit a broad mass range enabling the study of small precursor ions and heavy cluster ions at the same time. Weakly bound cluster ions can easily de-cluster during ion transfer depending on the voltages applied to the ion transfer optics. With the example system of H3O+(H2O)n=0–3, we estimate that cluster ions with higher binding energies than 17 kcal/mol can be transferred through the APi without significant fragmentation, which is considerably lower than about 25 kcal/mol estimated from the literature for APi-TOFs with quadrupole ion guides. In contrast to the low fragmenting ion transfer, the hexapoles can be set to a high fragmenting declustering mode for collision-induced dissociation (CID) experiments as well. The ion transmission efficiency over a broad mass range was determined to be in the order of 1 %, which is comparable to existing instrumentation. From measurements under well-controlled conditions during the CLOUD experiment, we demonstrate the instrument's performance and present results from an inter-comparison with a quadrupole based APi-TOF.