TY - JOUR A1 - Gschwind, S. A1 - Flamigni, L. A1 - Koch, J. A1 - Borovinskaya, O. A1 - Groh, S. A1 - Niemax, Kay A1 - Günther, D. T1 - Capabilities of inductively coupled plasma mass spectrometry for the detection of nanoparticles carried by monodisperse microdroplets N2 - Recently, first analyses of single sub-micrometre particles, embedded in liquid droplets, by inductively coupled plasma optical emission spectrometry (ICP-OES) with a size-equivalent detection limit of several hundred nanometres were reported.1,2 To achieve lower detection limits which might allow for the analysis of particles in the nanometre size range a more sensitive technique such as mass spectrometry (MS) is required. Various modifications of particle delivery and data acquisition systems commonly used were carried out to install a setup adequate for ICP-MS detection. These modifications enabled us to supply droplets generated by a commercial microdroplet generator (droplet size: 30–40 µm) with nearly 100% efficiency and high uniformity to the ICP. Analyses were performed using both standard solutions of dissolved metals at concentrations of 1 (Ag), 2 (Au), 5 (Au), or 10 (Cu) mg L-1 and highly diluted suspensions of gold and silver nanoparticles with sizes below 110 nm. In doing so, detection efficiencies of 10-6 counts per atom could be achieved while size-related limits of quantification were found to be 21 nm and 33 nm for gold and silver, respectively. Furthermore, the advantages of utilizing microdroplet generators vs. conventional nebulizers for nanoparticle analyses by ICP-MS are discussed. PY - 2011 DO - https://doi.org/10.1039/c0ja00249f SN - 0267-9477 SN - 1364-5544 VL - 26 IS - 6 SP - 1166 EP - 1174 PB - Royal Society of Chemistry CY - London AN - OPUS4-25606 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Murtazin, Ayrat A1 - Groh, S. A1 - Niemax, Kay T1 - Investigation of sample introduction- and plasma-related matrix effects in inductively coupled plasma spectrometry applying single analyte droplet and particle injection N2 - Analyte atomization in an inductively coupled argon plasma is studied with spatial and temporal resolution by simultaneous side- and end-on emission spectroscopy. The samples are either introduced as single monodisperse microdroplets of analyte solution or in form of spherical nano- or microparticles with narrow size distributions embedded in microdroplets. While end-on spectroscopy provides quantitative information on the total atomization process during the transport through the ICP of a single injection event, side-on measurements deliver the spatial positions of the processes. It is shown that there are significant spatial shifts of the position of analyte atomization in dependence on injector gas flow, droplet size, analyte mass, and the mass of accompanying elements. These shifts have direct influence on the size of the analyte clouds at a particular position in the ICP, e.g., at the position of the sampler of a mass spectrometer in ICP-MS, and, therefore, on the detection efficiency of this technique. Furthermore, the dynamic processes of analyte ionization as well as element dependent diffusion were studied with spatial and temporal resolution. KW - Matrix effects KW - ICP KW - Microdroplets PY - 2012 DO - https://doi.org/10.1016/j.sab.2011.12.003 SN - 0584-8547 SN - 0038-6987 VL - 67 SP - 3 EP - 16 PB - Elsevier CY - Amsterdam AN - OPUS4-25604 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lindner, H. A1 - Murtazin, Ayrat A1 - Groh, S. A1 - Niemax, Kay A1 - Bogaerts, A. T1 - Simulation and experimental studies on plasma temperature, flow velocity, and injector diameter effects for an inductively coupled plasma N2 - An inductively coupled plasma (ICP) is analyzed by means of experiments and numerical simulation. Important plasma properties are analyzed, namely, the effective temperature inside the central channel and the mean flow velocity inside the plasma. Furthermore, the effect of torches with different injector diameters is studied by the model. The temperature inside the central channel is determined from the end-on collected line-to-background ratio in dependence of the injector gas flow rates. Within the limits of 3% deviation, the results of the simulation and the experiments are in good agreement in the range of flow rates relevant for the analysis of relatively large droplets, i.e., ~ 50 µm. The deviation increases for higher gas flow rates but stays below 6% for all flow rates studied. The velocity of the gas inside the coil region was determined by side-on analyte emission measurements with single monodisperse droplet introduction and by the analysis of the injector gas path lines in the simulation. In the downstream region significantly higher velocities were found than in the upstream region in both the simulation and the experiment. The quantitative values show good agreement in the downstream region. In the upstream region, deviations were found in the absolute values which can be attributed to the flow conditions in that region and because the methods used for velocity determination are not fully consistent. Eddy structures are found in the simulated flow lines. These affect strongly the way taken by the path lines of the injector gas and they can explain the very long analytical signals found in the experiments at low flow rates. Simulations were performed for different injector diameters in order to find conditions where good analyte transport and optimum signals can be expected. The results clearly show the existence of a transition flow rate which marks the lower limit for effective analyte transport conditions through the plasma. A rule-of-thumb equation was extracted from the results from which the transition flow rate can be estimated for different injector diameters and different injector gas compositions. PY - 2011 DO - https://doi.org/10.1021/ac201699q SN - 0003-2700 SN - 1520-6882 VL - 83 IS - 24 SP - 9260 EP - 9266 PB - American Chemical Society CY - Washington, DC AN - OPUS4-25605 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Murtazin, Ayrat A1 - Groh, S. A1 - Niemax, Kay T1 - Measurement of element mass distributions in particle ensembles applying ICP-OES N2 - End-on inductively coupled plasma optical emission spectrometry (ICP-OES) of the relative mass distributions in ensembles of spherical SiO2 particles with small and large size variations is presented. The particles are introduced into the ICP by injection of monodisperse microdroplets generated from diluted particle suspensions. The spectroscopic signals, taking into account the peak or the integrated intensities of the Si 288.16 nm line, are compared with mass distribution measurements of corresponding SiO2 particle ensembles performed by Scanning Electron Microscopy (SEM). It is found that the relative mass distributions measured by ICP-OES are in good agreement with SEM measurements if the spectroscopic signal to noise ratio is sufficiently large indicating that intensity variations due to different particle trajectories in the ICP are less important than expected. PY - 2010 DO - https://doi.org/10.1039/c004946h SN - 0267-9477 SN - 1364-5544 VL - 25 IS - 9 SP - 1395 EP - 1401 PB - Royal Society of Chemistry CY - London AN - OPUS4-22982 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Diwakar, P.K. A1 - Groh, S. A1 - Niemax, Kay A1 - Hahn, D.W. T1 - Study of analyte dissociation and diffusion in laser-induced plasmas: implications for laser-induced breakdown spectroscopy N2 - Plasma–particle interactions are explored through the introduction of single microdroplets into laser-induced plasmas. Both spectroscopic analysis and direct imaging of analyte atomic emission are used to provide insight into the various fundamental processes, namely desolvation, atomization, and atomic diffusion. By doping the 50 µm droplets with Lu, Mg or Ca, the analyte excitation temperature and the ion-to-neutral emission ratio are explored as a function of plasma residence time following breakdown. The data suggest a change in the local plasma conditions about the analyte atoms around 15–20 µs following breakdown, which may be interpreted as an overall transition from localized (i.e. perturbed) plasma conditions to the global (i.e. bulk) plasma conditions. A direct assessment of the hydrogen atomic diffusion coefficient following analyte desolvation reveals a value of 1.7 m² s-1 in the first 250–500 ns. This value is in good overall agreement with a theoretical analysis and with an analytical treatment of a surface source of hydrogen atoms. In contrast, calcium emission is only observed beyond about 1 µs, with a diffusion coefficient at least an order of magnitude below the hydrogen value. The temporal H and Ca emission data suggest that water vaporizes first, leaving an ever increasing Ca analyte concentration until finally, with nearly all water desorbed, the Ca fraction is vaporized. Overall, the data support the conclusion that finite time-scales of heat and mass transfer play an important role in localized plasma perturbations in the vicinity of the analyte, which has important implications for the LIBS analyte signal. PY - 2010 DO - https://doi.org/10.1039/c0ja00063a SN - 0267-9477 SN - 1364-5544 VL - 25 IS - 12 SP - 1921 EP - 1930 PB - Royal Society of Chemistry CY - London AN - OPUS4-22983 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Asgill, Michael E. A1 - Groh, S. A1 - Niemax, Kay A1 - Hahn, D.W. T1 - The use of multi-element aerosol particles for determining temporal variations in temperature and electron density in laser-induced plasmas in support of quantitative laser-induced breakdown spectroscopy N2 - Quantitative laser-induced breakdown spectroscopy (LIBS) analysis operates on the assumption that the sample is completely dissociated and diffused within the highly energetic plasma on time-scales of analyte analysis, resulting in analyte emission ideally at the bulk plasma temperature and a signal that is linear with analyte mass concentration. However, recent studies focusing on aerosol analysis have found the heat and mass diffusion rates within laser-induced plasmas to be finite, resulting in particle-rich, locally perturbed areas within the hot bulk plasma. The goal of this study is to observe any related plasma differences, by calculating the bulk and local (i.e. analyte rich regions) plasma temperatures and electron density, to better understand the time frame of equilibrium between the local and bulk plasma properties. This study also seeks to determine whether the presence of large quantities of a matrix element can significantly alter the local plasma conditions, thereby generating matrix effects. We report the temporal profiles of particle-derived species, adding additional insight into the effect of local perturbation of plasma properties, with the conclusion that significant plasma residence (tens of microseconds) is necessary to minimize such effects. KW - Laser-induced breakdown spectroscopy KW - LIBS KW - Matrix effects KW - Aerosol analysis PY - 2015 DO - https://doi.org/10.1016/j.sab.2015.04.005 SN - 0584-8547 SN - 0038-6987 VL - 109 SP - 1 EP - 7 PB - Elsevier CY - Amsterdam AN - OPUS4-33733 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -