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Laser-induzierte Plasmaspektroskopie zur Prozessanalytik an Schlacken im elektrischen Lichtbogenofen
(2013)
Infraredmatrix-assisted laser dispersion and ionization(IR-MALDI) in combination with on mobility (IM) spectrometry enables the direct Analysis of biomolecules in aqueous solution. The release of ions directly from an aqueous solution is based on a phase explosion, induced by the Absorption of an IR laser pulse, which disperses the liquid as vapor, nano- and micro-droplets. The ionization process is characterized initially by a broad spatial distribution of the ions, which is a result of complex fluid dynamics and desolvation kinetics. These processes have a profound effect on the shape and width of the peaks in the IM spectra. In this work, the Transport of ions by the phase explosion-induced shockwave could be studied independently from the transport by the electric field. The shockwave-induced mean velocities of the ions at different time scales were determined through IM spectrometry and shadowgraphy. The results show a deceleration of the Ions from 118m∙s−1 at a distance of 400 μm from the liquid surface to 7.1 m∙s−1 at a distance of 10 mm, which is caused by a pileup effect. Furthermore, the desolvation kinetics were investigated
and a first-order desolvation constant of 325 ± 50 s−1
was obtained. In the second part, the IR-MALDI-IM
spectrometer is used as an HPLC detector for the twodimensional separation of a pesticide mixture.
A novel ionization scheme for ambient mass spectrometry is presented and discussed. Desorption and ionization are achieved by a quasi-continuous laser induced plasma (LIP) ignited in front of the atmospheric pressure interface of a time-of-flight mass spectrometer. This setup comprises the advantages of i) an ambient probe, ii) electro neutrality, iii) low power consumption, iv) a sufficient duty cycle, v) a ubiquitous plasma medium (air) and vi) high sensitivity caused by the high electron number densities.
The plasma properties and operating conditions are investigated to understand the processes that lead to the formation of molecular ions. Comprehensive studies include optical emission spectroscopy, shadowgraphic shockwave visualization and time-of-flight mass spectrometry investigations. The observed MS signal (including reagent-ion signal, as well as analyte spectra) closely resembles the ionization behavior of other electrically-driven plasma-based ionization sources, such as DBD, LTP or DART. Conversely that means that although LIPs are commonly known to have temperatures way above 10.000 K and thus efficiently atomize and ionize molecules, MS spectra were obtained that showed the formation of intact molecular ions.
For an insight into the LIP properties the optical emission of the LIP is examined and exhibits a pronounced degree of dissociation into atomic and ionic species, which reflects the higher temperature and electron density inside a LIP. Accordingly, rather elemental (ICP-type) than molecular spectra should be expected. However due to the absence of such ions, we conclude that the analyte does not enter the hot center of the plasma itself. Moreover, the initial, highly-excited plasma species react cascade-like to lower energetic species via reactive collision with the surrounding atmosphere, which can then subsequently ionize molecules of interest. The concept potentially involves charge transfer, proton transfer, electron impact and photoionization.
These assumptions are confirmed via the shadowgraphs of the expanding shockwave around the LIP. An effective spatial separation between the two regions is maintained by concentrically expanding pressure waves resulting in a strongly unidirectional diffusion. Additionally, the strictly outbound matter transport suggests a rarefaction inside the plasma region for each plasma event.
A novel ionization scheme for ambient mass spectrometry is presented and discussed. Desorption and ionization are achieved by a quasi-continuous laser induced plasma (LIP) ignited in front of the atmospheric pressure interface of a time-of-flight mass spectrometer. This setup comprises the advantages of i) an ambient probe, ii) electro neutrality, iii) low power consumption, iv) a sufficient duty cycle, v) a ubiquitous plasma medium (air) and vi) high sensitivity caused by the high electron number densities.
The plasma properties and operating conditions are investigated to understand the processes that lead to the formation of molecular ions. Comprehensive studies include optical emission spectroscopy, shadowgraphic shockwave visualization and time-of-flight mass spectrometry investigations. The observed MS signal (including reagent-ion signal, as well as analyte spectra) closely resembles the ionization behavior of other electrically-driven plasma-based ionization sources, such as DBD, LTP or DART. Conversely that means that although LIPs are commonly known to have temperatures way above 10.000 K and thus efficiently atomize and ionize molecules, MS spectra were obtained that showed the formation of intact molecular ions. For an insight into the LIP properties the optical emission of the LIP is examined and exhibits a pronounced degree of dissociation into atomic and ionic species, which reflects the higher temperature and electron density inside a LIP. Accordingly, rather elemental (ICP-type) than molecular spectra should be expected. However due to the absence of such ions, we conclude that the analyte does not enter the hot center of the plasma itself. Moreover, the initial, highlyexcited plasma species react cascade-like to lower energetic species via reactive collision with the surrounding atmosphere, which can then subsequently ionize molecules of interest. The concept potentially involves charge transfer, proton transfer, electron impact and photoionization.
These assumptions are confirmed via the shadowgraphs of the expanding shockwave around the LIP. An effective spatial separation between the two regions is maintained by concentrically expanding pressure waves resulting in a strongly unidirectional diffusion. Additionally, the strictly outbound matter transport suggests a rarefaction inside the plasma region for each plasma event.
Lithium exists in two stable isotopes, 6Li and 7Li. The ratio of these in every ore varies depending on the geological history of the sample, thus providing a tool for fingerprinting the distinct origin of Li containing samples. Determination of the exact isotope ratio for e.g. designation of provenance today relies on expensive and bulky instrumentation such as multi `collector inductively coupled plasma mass spectrometry` (MC-ICP-MS). These instruments, however, are known to bear pitfalls in the characterization of particular elements including Lithium. BAM recently developed two alternative analytical devices for this task, solely relying on inexpensive optical spectroscopy in combination with state-of-the-art multivariate data analysis such as Machine learning algorithms. Both techniques have been comprehensively studied using certified reference materials and comparing the results to MC-ICP-MS results and could be shown to result in comparable figures of merit, paving the way for a more general accessibility to provenance determination instrumentation. The results also pave the way towards even further simplification of the laboratory infrastructure demands and to further include additional elements into the isotopic fingerprinting methodology.
Laser-induced plasma (LIP) has drawn significant amount of attentions in the past decades, particular in elemental analyses for solid or liquid samples. Through proper focusing of the highly energetic laser beam, the plasma can also be ignited in the ambient air, where airborne analytes can be ionized. Such an effect enabled the use of airborne LIP as an ambient ionization source for mass spectrometric analyses. In contrast to other ambient desorption/ionization sources, airborne LIP does not require a specific discharge medium or expensive gas stream. Meanwhile, the airborne LIP produces reagent ion species for both proton-transfer and charge-transfer reactions in addition to the vacuum ultraviolent photons that are capable of promoting single photon ionization, which can be utilized to ionize polar and non-polar analytes. In order to gauge the analytical performance of airborne LIP, it is critical to understand the undergoing chemistry and physics during and after the plasma formation.
Due to the ambient nature of airborne LIP, the variations of air composition and flow strongly affect the plasma behaviors. Preliminary result suggested the addition of a laminar flow of nitrogen gas favored the formation of protonated species (MH+) against the molecular ones (M+). Although the gas addition approach cannot fully tune the ionization process towards the specific production of pseudo-molecular species versus molecular ones, the alternation of molecular ion formation can be used for analyte recognitions through post processing of the ion patterns. The pulsed character of the used lasers makes the reagent ion equilibrium both transient- and highly fluid-dynamically controlled. The acoustic shock-waves induced by the airborne LIP get affected by an applied gas streams towards the plasma center, influencing the molecular-ion and ion-ion interactions in the near proximity of the plasma.
To understand the airborne LIP formation, the temporally and spatially resolved optical emission spectra were recorded. The results will be correlated to time-resolved mass-spectrometric investigations of the ion profile during different stages of the plasma formation. As one example, the formation of pyrylium ion originating from aromatic compounds will be highlighted.
Currently, research in chemical manufacturing moves towards flexible plug-and-play approaches focusing on modular plants, capable of producing small scales on-demand with short down-times between individual campaigns. This approach allows for efficient use of hardware, a faster optimization of the process conditions, and thus, an accelerated introduction of new products to the market. Driven mostly by the search for chemical syntheses under biocompatible conditions, so-called “click” chemistry rapidly became a growing field of research. The resulting simple one-pot reactions are so far only scarcely accompanied by an adequate optimization via comparably straightforward and robust analysis techniques.
Here we report on a fast and reliable calibration-free online high field NMR monitoring approach for technical mixtures. It combines a versatile fluidic system, continuous-flow measurement with a time interval of 20 s per spectrum, and a robust, automated algorithm to interpret the obtained data. All spectra were acquired using a 500 MHz NMR spectrometer (Varian) with a dual band flow probe having a 1/16-inch polymer tubing working as a flow cell. Single scan 1H NMR spectra were recorded with an acquisition time of 5 s, relaxation delay of 15 s. As a proof-of-concept, the thiol-ene coupling between N-boc cysteine methyl ester and allyl alcohol was conducted in non-deuterated solvents while its time-resolved behaviour was characterised with step tracer experiments.
Through the application of spectral modeling the signal area for each reactant can be deconvoluted in the online spectra and thus converted to the respective concentrations or molar ratios. The signals which were suitable for direct integration were used herein for comparison purposes of both methods.