TY - JOUR A1 - van Wasen, S. A1 - You, Yi A1 - Beck, S. A1 - Riedel, Jens A1 - Volmer, D. A. T1 - Miniaturized Protein Digestion Using Acoustic Levitation with Online High Resolution Mass Spectrometry N2 - The combination of acoustically levitated droplets, mid-IR laser evaporation, and subsequent post-ionization by secondary electrospray ionization was applied for monitoring the enzymatic digestion of various proteins. Acoustically levitated droplets are an ideal, wall-free model reactor, readily allowing compartmentalized microfluidic trypsin digestions. Time-resolved interrogation of the droplets yielded real-time information on the progress of the reaction and thus provided insights into reaction kinetics. After 30 min of digestion in the acoustic levitator, the obtained protein sequence coverages were identical to the reference overnight digestions. Importantly, our results clearly demonstrate that the applied experimental setup can be used for the real-time investigation of chemical reactions. Furthermore, the described methodology only uses a fraction of the typically applied amounts of solvent, analyte, and trypsin. Thus, the results exemplify the use of acoustic levitation as a green analytical chemistry alternative to the currently used batch reactions. KW - Acoustic levitation KW - Protein analysis KW - Mass spectrometry PY - 2023 DO - https://doi.org/10.1021/acs.analchem.2c05334 VL - 95 SP - 4190 EP - 4195 PB - ACS Publications AN - OPUS4-57053 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Li, Xunyu A1 - Riedel, Jens A1 - You, Yi T1 - Practical high-resolution spectroscopy with a spatial heterodyne spectrometer: Determination of instrumental function for lineshape recovery N2 - The spatial heterodyne spectrometer (SHS) is a well-recognized platform for its high resolving power in various use cases of spectroscopy. Same as other spectrometer topologies, the SHS, unfortunately, also suffers from classical challenges such as distorted lineshape due to the instrumental function. The goal of this work is to tackle this persisting issue through a simple numerical approach. With the inherent characteristics of an SHS interferogram, we report the direct extraction and determination of the instrumental function in its numerical representation from an SHS interferogram; this instrumental function was further used for spectral data processing that enables significant improvements in spectral resolution through deconvolution algorithms.Here, we systematically discuss the recognition of the embedded instrumental function among various ingredients within an interferogram. To verify the numerical approach, lithium was chosen as the model sample, resembling the use of SHS in an isotopic analysis application. Specifically, the resonance transition of lithium D-lines (2P1/2,3/2 ← 2S1/2) was selected to assess the performance of the spectral processing. With the spectral deconvolution, the spectral features that represent the 6Li and 7Li were nearly baseline-separated, allowing for the accurate measure of the isotopic abundance without external references or algorithm adjustments (e.g., curve fitting). KW - SHS KW - Isotopic analysis KW - High Resolution PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-613401 DO - https://doi.org/10.1016/j.sab.2024.107053 SN - 0584-8547 VL - 221 SP - 1 EP - 5 PB - Elsevier AN - OPUS4-61340 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - You, Yi A1 - Danischewski, Julia A1 - Molnar, Brian A1 - Riedel, Jens A1 - Shelley, Jacob T1 - Manipulation of Gaseous Ions with Acoustic Fields at Atmospheric Pressure N2 - The ability to controllably move gaseous ions is an essential aspect of ion-based spectrometry (e.g., mass spectrometry and ion mobility spectrometry) as well as materials processing. At higher pressures, ion motion is largely governed by diffusion and multiple collisions with neutral gas molecules. Thus, high-pressure ion optics based on electrostatics require large fields, radio frequency drives, complicated geometries, and/or partially transmissive grids that become contaminated. Here, we demonstrate that low-power standing acoustic waves can be used to guide, block, focus, and separate beams of ions akin to electrostatic ion optics. Ions preferentially travel through the static-pressure regions (“nodes”) while neutral gas does not appear to be impacted by the acoustic field structure and continues along a straight trajectory. This acoustic ion manipulation (AIM) approach has broad implications for ion manipulation techniques at high pressure, while expanding our fundamental understanding of the behavior of ions in gases. KW - Ion mobility spectrometry KW - Acoustic KW - Mass spectrometry PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-600704 DO - https://doi.org/10.1021/jacs.4c01224 SP - 1 EP - 6 PB - ACS Publications AN - OPUS4-60070 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - van Wasen, S. A1 - You, Yi A1 - Beck, S. A1 - Riedel, Jens A1 - Volmer, D. A. T1 - Laser Ablation Secondary Electrospray Ionization for In Situ Mass Spectrometric Interrogation of Acoustically-Levitated Droplets N2 - The composition of acoustically levitated droplets was probed by a novel combination of mid-IR laser evaporation and subsequent postionization via secondary electrospray ionization. The combination of microliter samples and subnanoliter sampling provided time-resolved interrogation of droplets and allowed for a kinetic investigation of the laser-induced release of the analyte, which was found to strongly depend on the analytes. The observed substancespecific delayed release of the analytes permitted baseline-separated discrimination of the analytes, ideal for the study of complex samples. The additionally applied postionization scheme was found to enable efficient detection of small volatile compounds as well as peptides. The detection of small molecules and peptides occurred under very different sampling geometries, pointing to two distinct underlying ionization mechanisms. Overall, our results suggest that the experimental setup presented in this study can serve as a widely applicable platform to study chemical reactions in acoustically levitated droplets as model reactors. KW - Acoustic levitation KW - Mass spectrometry KW - Electrospray KW - Laser ablation PY - 2022 DO - https://doi.org/10.1021/acs.analchem.2c03800 SN - 0003-2700 VL - 2022 SP - 1 EP - 5 PB - ACS Publications CY - Washington AN - OPUS4-56531 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - You, Yi T1 - MicroPhase: An Open-Source Flexible Ultrasonic Phased Array Based on Microcontrollers N2 - The use of resonant acoustic fields has gained significant attention due to their capability for contactless manipulation of objects in the open air and other media, referred to as ultrasonic levitation. To overcome the limitations in air-coupling efficiency, Langevin-type ultrasonic transducers are often employed, as they can operate at relatively high power, ranging from several tens to thousands of watts. However, such platforms typically lack the ability to move acoustically trapped objects efficiently, often requiring additional mechanical structures for even basic motion control, such as translation. In contrast, ultrasonic phased arrays offer clear advantages by leveraging their inherent beam-forming capabilities, which allows for dynamic shaping of acoustic fields in situ. Unfortunately, phased array control systems are not readily accessible, particularly when specific geometric or performance criteria must be met. Most commercially available phased array controllers are designed to operate in the MHz range; those are suitable only for high acoustic impedance media, such as water. Conversely, platforms for open-air applications typically utilize ultrasonic speakers operating at 40 kHz. In both cases, these systems are built on field-programmable gate arrays (FPGAs). However, interfacing FPGAs with computers and developing FPGA firmware (e.g., in VHDL) can be technically demanding, and analog components such as power amplifiers further complicate the system design. These limitations severely restrained the use of flexible ultrasonic levitations in analytical chemistry. Here, we present a novel platform for controlling ultrasonic phased arrays using single modern microcontrollers. This platform leverages the connectivity features of microcontrollers, allowing straightforward interfacing with computers via common programming languages (e.g., Python). The system employs fast direct memory access (DMA) to control up-to 256 ultrasonic transducers with a resolution of 0.5 µs, which is suitable for air-based applications in the 20-50 kHz range. Additionally, the platform can interface with traditional Langevin-type transducers, enabling their conversion into phased arrays. Optical characterization of acoustic field optimization is also discussed. T2 - ANAKON 2025 CY - Leipzig, Germany DA - 10.03.2025 KW - Acoustic ion manipulation PY - 2025 AN - OPUS4-64112 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Xue, Boyang A1 - Wang, Zhangjun A1 - Zhu, Tao A1 - Gu, Yezhen A1 - Sun, Weihong A1 - Chen, Chao A1 - Li, Zhigang A1 - Riedel, Jens A1 - You, Yi T1 - High repetition-rate laser-induced breakdown spectroscopy combined with two-dimensional correlation method for analysis of sea-salt aerosols N2 - Laser-induced breakdown spectroscopy (LIBS) offers a tantalizing glimpse into real-time, on-the-spot aerosol analysis. Yet, the reliance on traditional lasers, with their limitations in energy and frequency, hampers optimal sample handling, dissociation, and excitation. To address those challenges, we propose a novel tactic: utilize a high repetition-rate (rep.-rate) laser with low pulse energy in combination with the two-dimensional correlation (2D-corr.) technique for sea-salt aerosols analyses. By examining the emission patterns from both the laser pulse train and individual pulses, we recognize distinctive analyte-specific rep.-rate responses, which allowed spectral reconstruction of analytes, avoiding background interferences. This discovery enabled the rep.-rate modulation for a 2D-corr. spectroscopy workflow. Consequently, we successfully differentiated between particle-related and air-species-related spectral components, obviating expensive spectrometers or intensified image detectors. For instance, the Na I at 589 nm stemming from aerosols exhibited an entirely different correlation contribution compared to O I at 777 nm, resulting in reconstructed clean aerosol-spectra without spectral peaks originated from air species. This 2D-corr. aerosol LIBS approach shows promising analytical potential streamlining aerosol particle analysis. KW - LIBS KW - Aerosol PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-613392 DO - https://doi.org/10.1016/j.sab.2024.107048 SN - 0584-8547 VL - 221 SP - 1 EP - 8 PB - Elsevier AN - OPUS4-61339 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Li, Xunyu A1 - Riedel, Jens A1 - You, Yi T1 - Spectrally resolved lithium isotope quantification through high-resolution spatial heterodyne spectrometry N2 - Isotope ratio determination of lithium is increasingly important in fields ranging from geochemistry to battery diagnostics. While mass spectrometry remains the gold standard, it is costly, cumbersome, and incompatible with portable or inline implementations. Optical emission spectroscopy presents an appealing alternative. However, it is traditionally limited by insufficient spectral resolution or resolving power to separate lithium isotope emissions due to their generalized designs for a wide spectral range; this often requires overly complicated algorithms to overcome the instrumental drawbacks. (79) Results Here, we report a high-resolution optical method for lithium isotope quantification using a custom-built spatial heterodyne spectrometer (SHS) combined with a reduced-pressure glow discharge source. This configuration yielded a resolving power of 189,000 and enabled baseline resolution of lithium d-line emission features even without the need for preliminary data processing. Despite the inherent low sensitivity of SHS, a detection limit of 30 pmol was achieved using a standard industrial camera. To improve quantitative accuracy, we introduced a deconvolution-based spectral lineshape recovery technique alongside a bootstrapping-based error propagation strategy. These methods facilitated robust isotope ratio calibration using both peak-height and peak-area metrics. The SHS platform additionally enabled the determination of relative transition probabilities, suggesting the feasibility of calibration-free operation. This work demonstrates the practical viability of SHS for high-specificity, high-resolution lithium isotope analysis. The approach is compact, potentially field-deployable, and adaptable to other elements with optically resolvable isotope shifts, offering a route toward accessible and calibration-free optical isotopic analyses. KW - SHS KW - Isotope KW - High-resolution spectroscopy PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-635139 DO - https://doi.org/10.1016/j.aca.2025.344329 SN - 1873-4324 VL - 1368 SP - 1 EP - 8 PB - Elsevier B.V. AN - OPUS4-63513 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mohan, M. A1 - Prochazka, D. A1 - You, Yi A1 - Riedel, Jens A1 - Gornushkin, Igor A1 - Rocnakova, I. A1 - Papula, M. A1 - Porízka, P. A1 - Kaizer, J. T1 - Investigating plasma morphology at material boundaries under varying ambient pressures N2 - Laser-Induced Breakdown Spectroscopy (LIBS) is a widely used technique for elemental analysis. The analysis of the obtained LIBS spectra generally assumes plasma homogeneity. However, using focused laser beams for interrogation, LIBS probes materials on the microscale and is, thus, prone to artefacts from sample heterogeneities on the micrometer scale. An ablation at a material boundary of two matrices may result in a significant inhomogeneity in the plasma plume, which can severely impact the accuracy of quantitative analysis. Since this propagation of the surface morphology into the plasma plume is driven by the plasma expansion, its final impact is strongly pressure dependent. This study examines the influence of varying ambient pressures (7–1000 mbar) on plasma morphology, spectral characteristics, and key plasma properties such as electron number density at a well-defined Cu–Sn boundary, in comparison with the results obtained using homogeneous alloys. Several approaches of plasma imaging with bandpass filters, spectroscopy, and Radon transform-based 3D reconstruction were employed to analyze elemental distribution, signal-to-noise (SNR) and signal-to-background (SBR) ratios, as well as electron number densities. The 3D reconstructions revealed a pronounced plasma asymmetry for the ablation at the material boundary, in contrast to the near-axial symmetry observed for the ablation of homogeneous alloys. At lower pressures, this distinct elemental separation in plasma persisted, while higher pressures led to an increased collisional mixing and homogenization. SNR and SBR were consistently lower for ablation at the boundary compared to homogeneous samples. These findings highlight how boundary ablation contributes to plasma inhomogeneities in LIBS analysis of heterogeneous materials and emphasize the need to account for these effects when using LIBS for elemental mapping of fine heterogeneous structures. KW - Laser-induced breakdown spectroscopy KW - Plasma inhomogeneity KW - Plasma tomography KW - Radon transform KW - Material boundaries KW - Ambient pressure effects PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-634777 DO - https://doi.org/10.1016/j.talanta.2025.128377 SN - 1873-3573 VL - 295 SP - 1 EP - 8 PB - Elsevier B.V. AN - OPUS4-63477 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - You, Yi T1 - Differential Mobility Analysis with Acoustic Ion Manipulation (AIM) N2 - Ion mobility analyses provide complementarity to mass spectrometry in analyte ion identification through the introduction of a higher-pressure separation modality. The recently discovered acoustic ion manipulation (AIM) phenomenon, which exploits unique behaviors of ions in acoustic fields, presents a novel, electric-field-free means to distinguish ions by mobility. In one form of AIM, a static pressure field in an ultrasonic resonator causes a displacement of the ion stream toward the node region, when initially directed toward the antinode. When the static field strength falls below the threshold for all ion deflection, the partitioning reflects ion-specific acoustic mobilities or acoustic radiation impedance. This study demonstrates ion-oriented mobility separation with the AIM approach for mass-spectrometric analysis. An Orbitrap mass spectrometer was used to record ion signal variations as a function of acoustic field strength. An acoustic pressure source with a transducer–reflector configuration was used to generate a standing acoustic wave for partial ion deflection. The drive frequency was swept near resonance to modulate the static pressure field. An alternating-current (AC) plasma discharge source was used to produce an ion beam directed toward an antinode of the resonant structure and later deflected into the mass spectrometer inlet with the acoustic field. Several small molecule analytes, including methanol, ethanol, acetone, and toluene, were doped in the discharge gas to distinguish ions formed in the source from those produced in transit to the MS inlet. An ion beam, offset relative to the inlet capillary of the mass spectrometer, yielded minimal ion detection in the absence of the resonant acoustic field. A sweep of the frequency near resonance induced a low–high–low transition in the static pressure within the resonator. Consequently, the total ion signal as a function of drive frequency resembled a horn gain curve, which is commonly recognized as a key characteristic in ultrasonic transducer design. Maximum ion signal was attained at the resonance frequency, while a pronounced minimum occurred at the anti-resonance frequency. Analysis of drive frequency response curves for distinct ion peaks revealed that source-generated ions displayed a congruent pattern to the overall ion count, thereby suggesting the formation of clusters prior to the vacuum region of the mass spectrometer. A finer frequency scan near the resonance region differentiated these clusters. For instance, response curves for toluene-related ions are slightly deviated from those associated with alcohols. Notably, a series of ions, presumably originating from an identical chemical precursor, manifested an entirely distinctive drive frequency response; their maximal signal occurred at a frequency not associated with any characteristic of the acoustic system or its electronics. The frequency response curves of the ions allowed implementation of a modified cross-correlation (mXcorr) algorithm to categorize ions according to chemical origin or clustering. The use of frequency, rather than the transducer voltage/power, offers the advantage of electronically measuring the horn gain curve in tandem with ion-specific analysis. This gain curve subsequently serves as a reference to decode latent chemical information for enhanced analytical accuracy. T2 - ASMS 2025 Conference CY - Baltimore, MA, USA DA - 01.06.2025 KW - Acoustic Ion Manipulation KW - Mass Spectrometry PY - 2025 AN - OPUS4-63512 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - You, Yi A1 - Xue, Boyang A1 - Riedel, Jens T1 - Enhancement of LIBS plasma in air with organic solvent vapors N2 - Laser-induced breakdown spectroscopy (LIBS) offers versatile, field-deployable elemental analysis; however, compact, high-repetition-rate nanosecond laser systems typically face constraints in power consumption and size, often compromising emission intensity and thus analytical performance. We demonstrate a significant improvement in LIBS signals through the controlled introduction of common organic solvent vapors into a sheath gas, with a diode-pumped solid-state laser (1064 nm, 2–28 kHz repetition rate, 450–600-μJ pulse energy). Optical and acoustic diagnostics reveal up to ca. 40-fold enhancement of the N II emission line at 567 nm when ambient air serves as the analyte. Maximal enhancement occurs at intermediate repetition rates of ca. 15 kHz, particularly at pulse energies approaching the optical breakdown threshold; this observation suggests a viable strategy for operating LIBS at lower pulse energies and higher repetition rates. Enhancement effects scale jointly with both vapor pressure and ionization energy of the organic species, with acetone and toluene markedly outperforming methanol and isopropanol. These findings provide a rational foundation for significantly improving the analytical performance of portable LIBS instruments without exceeding platform-specific constraints. KW - LIBS PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-653758 DO - https://doi.org/10.1016/j.sab.2025.107309 SN - 0584-8547 VL - 236 SP - 1 EP - 6 PB - Elsevier B.V. AN - OPUS4-65375 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -