Liquid Nebulization Research Articles

Volatile Species Generation for Trace Element and Speciation Analysis – Current State and Future Perspectives

Volatile Species Generation for Trace Element and Speciation Analysis – Current State and Future Perspectives

A chip-based supersonic microfluidic nebulizer for efficient sample introduction into inductively coupled plasma – Mass spectrometry

As the use of microfluidic chips for handling biological samples is increasing, so is the need for combining them with powerful analytical techniques for metal determination such as inductively-coupled plasma mass spectrometry (ICP-MS). So far, coupling a microfluidic chip to an ICP-MS has been demonstrated mainly through the use of conventional pneumatic micro-flow nebulizers. However, disadvantages associated with the use of such nebulizers entail dead volume issues and liquid suction exerted on the outlet channel of the chip. Herein, we propose that a microfluidic chip, bearing a pneumatic nozzle for liquid nebulization, has the potential to advance metal determination in chip-based ICP-MS. More specifically, we demonstrate for the first time that the coupling of a chip-based supersonic microfluidic nebulizer (chip-μf-Neb) to an ICP-MS can be conveniently achieved through the use of a spray chamber with a laminar flow makeup gas. Operation of the combined system was evaluated at low liquid flow rates across 0.5–20 μL min−1, while nebulization and makeup argon (Ar) gas flow rates were optimized with respect to maximizing indium (In) sensitivity and minimizing oxide formation; a maximum sensitivity of 40000 cps (μg L−1)−1 was achieved at 10 μL min−1. The system was further evaluated for its performance in single-particle analysis, featuring a transport efficiency of 46% for Ag nanoparticles. Finally, the capabilities for conducting single-cell analysis were demonstrated with the detection of 80Se and 75As in individual Chlamydomas reinhardtii cells, which were previously incubated in 20 μM of selenate and 300 μM of arsenate, respectively. Efficient operation at low liquid flow rates along with the absence of self-aspiration render this nebulizer a promising tool for combining the powerful field of microfluidics with metal quantitation by means of ICP-MS.

Micro-tapered aperture nebulization ionization for versatile mass spectrometry analysis.

The bloom of new ionization sources is promoting the prosperity and application of mass spectrometry analysis. In this study, we introduced a new (high) voltage-free ionization method termed micro-tapered aperture nebulization ionization (MANI), which only requires the use of a common micro-tapered aperture atomizer to operate. It is found that liquid nebulization on this type of atomizer can induce ionization of the dissolved analytes in the droplets without the assistance of additional voltage and gas. By assembling the commercially available atomizer module into a 3D-printed chamber, a compact MANI source was constructed and then characterized. This source has a high ion yield and satisfactory quantitative performance, and it is preferably used to analyze aqueous solutions. Furthermore, it exhibits broad applicability and can be easily extended to multiple applications, including liquid extraction surface analysis of solid samples and direct analysis of gaseous analytes via secondary spray ionization. In short, the MANI source is a simple, safe, green, and versatile tool that can assist mass spectrometers to perform routine and diverse analysis.

Efficient photochemical vapor generation of bismuth using a coiled Teflon reactor: Effect of metal sensitizers and analytical performance with flame-in-gas-shield atomizer and atomic fluorescence spectrometry

Photochemical vapor generation (PVG) of bismuth was accomplished in a simple flow–injection system with a standard Hg low-pressure tube lamp and a coiled Teflon reactor. The influence of a reaction medium flow rate (irradiation time) and composition was investigated using a miniature diffusion flame atomizer and high-resolution continuum source atomic absorption spectrometry. Combination of 40% (v/v) acetic acid, 1.25% (v/v) formic acid and a metal sensitizer at a flow rate of 3 mL min−1 (irradiation time of 90 s) was found optimal. The use of various metals as sensitizers was studied to initiate and enhance PVG substantially. The evident positive effect was found for four metal cations and the enhancement effect was in the following order: Cu2+<Cd2+<Fe2+ ≪ Co2+. At 50 mg L−1 Co2+ as the sensitizer, the overall PVG efficiency of 54 ± 2% was determined from relative comparison of sensitivities obtained with PVG and liquid nebulization coupled simultaneously to inductively coupled plasma mass spectrometry. In order to reach low limits of detection (LOD) at low operation cost, a coupling of PVG to atomic fluorescence spectrometry was tested and conditions of atomization in two flame atomizers were optimized. A blank-limited LOD of 12 ng L−1 was obtained with an advanced flame-in-gas-shield atomizer, which competes with PVG coupled to inductively coupled plasma mass spectrometry (5 ng L−1). Interferences from commonly used inorganic acids (HNO3, HCl and H2SO4) and other elements (As3+, Pb2+, Sb3+, Se4+ and Te4+) were also investigated and the accuracy was verified by analysis of water Standard Reference Material NIST 1643f.

Mass spectrometric assay of high radiopurity solid polymer materials for parts in radiation and rare event physics detectors

Abstract Plastic dielectric materials are required in radiation and rare event physics detectors as structural parts, insulators, seals, light reflectors, and in connectors. In order to observe events of interest rather than counting the radioactivity of the detector itself, these materials must be of high radiopurity. Using a mass spectrometric method, a number of solid plastic materials and parts were analyzed for mass levels of contaminants 232 Th and 238 U, which were used as an assessment of radiopurity. Sample preparation began with dry ashing the solid subsamples in very low mass containers of ultra low background electroformed copper (ULB EF-Cu) foil that had been cut and folded into boats serving as crucibles. Final determinations were carried out by inductively coupled plasma mass spectrometry (ICP-MS) with liquid nebulization sample solution introduction. Sample sizes were in the 25 mg to 1.25 g mass, and analyses could be completed in less than two days. Detection limits to pg/g (i.e, parts per trillion) levels are obtained and converted to radioactivity units μ Bq/kg of material. Determinations on poly(methyl methacrylate) (PMMA) gave values for 238 U below 10 μ Bq/kg, while values for poly(chlorotrifluoroethylene) (PCTFE) rod stock material or acid-leached machined PCTFE parts were at or below 50 μ Bq/kg in 238 U. Results for solid Purad poly(vinylidene fluoride) (PVDF) material are also reported at ca 5 mBq/kg of 238 U, although PVDF Solef 1010 raw material in powder and pellet form has been previously reported as low as 25 μ Bq/kg, and 200 μ Bq/kg 238 U, respectively. An analysis of a polyetherimide (PEI) material, sold as ULTEM, indicated promising radiopurity with a found value of 30 μ Bq/kg for 238 U. A variety of solid dielectric polymer materials were found with radiopurities at less than a mBq/kg 238 U and 232 Th.

Efficient Photochemical Vapor Generation of Molybdenum for ICPMS Detection.

Photochemical vapor generation (PVG) of Mo was accomplished using a 19 W high-efficiency flow-through photoreactor operating in a flow injection mode using 30-50% (w/v) formic acid as a reaction medium. The generated volatile product (most probably molybdenum hexacarbonyl) was directed by an argon carrier gas to a plastic gas-liquid separator and introduced into the spray chamber of an inductively coupled plasma mass spectrometer for detection. Particular attention was paid to the determination of overall PVG efficiency relative to that for liquid nebulization. Utilizing a sample flow rate of 1.25 mL min-1, corresponding to an irradiation time of 38 s, PVG efficiencies in the range 46-66% were achieved. The efficiency could be further enhanced by the presence of mg L-1 added Fe3+ ions. A limit of detection of 1.2 ng L-1 and precision of 3% (RSD) at 250 ng L-1 were achieved. Interferences from inorganic anions likely to be encountered during analytical application to real samples (NO3-, Cl-, SO42-, NO2-, and ClO4-) were investigated in detail. The accuracy and applicability of this sensitive methodology was successfully verified by analysis of fresh water Standard Reference Material NIST 1643e, two seawater Certified Reference Materials (NASS-7 and CASS-6), and by analysis of two samples of commercial dietary supplements solubilized in formic acid.

Liquid Nebulization-Ion Mobility Spectrometry Based Quantification of Nanoparticle-Protein Conjugate Formation.

Despite the importance of examining the formation of nanoparticle-protein conjugates, there is a dearth of routine techniques for nanoparticle-protein conjugate characterization. The most prominent change to a nanoparticle population upon conjugate formation is a shift in the nanoparticle size distribution function. However, commonly employed dynamic light scattering based approaches for size distribution characterization are ineffective for nonmonodisperse samples, and further they are relatively insensitive to size shifts of only several nanometers, which are common during conjugate formation. Conversely, gas phase ion mobility spectrometry (IMS) techniques can be used to reliably examine polydisperse samples, and are sensitive to ∼1 nm size distribution function shifts; the challenge with IMS is to convert nanoparticle-protein conjugates to aerosol particles without bringing about nonspecific aggregation or conjugate formation. Except in limited circumstances, electrospray based aerosolization has proven difficult to apply for this purpose. Here we show that via liquid nebulization (LN) with online, high-flow-rate dilution (with dilution factors up to 10 000) it is possible to aerosolize nanoparticle-protein conjugates, enabling IMS measurements of their conjugate size distribution functions. We specifically employ the LN-IMS system to examine bovine serum albumin binding to gold nanoparticles. Inferred maximum protein surface coverages (∼0.025 nm(-2)) from measurements are shown to be in excellent agreement with reported values for gold from quartz crystal microbalance measurements. It is also shown that LN-IMS measurements can be used to detect size distribution function shifts on the order of 1 nm, even in circumstances where the size distribution function itself has a standard deviation of ∼5 nm. In total, the reported measurements suggest that LN-IMS is a potentially simple and robust technique for nanoparticle-protein conjugate characterization.

Internal standardization using a dual mode sample introduction system in the determination of As by HG-ICP-MS

Internal standardization was studied by introducing internal standards simultaneously by liquid nebulization (Y, Pd) and hydride generation (Ge, Bi) with a dual mode sample introduction system in the determination of arsenic by HG-ICP-MS. The effects of the gas flow rates and ICP-MS parameters were examined for all the elements. Sample introduction for Ge and Bi is similar to arsenic and therefore they could correct the signal variations originating from the hydride generation sample introduction system. The results indicated, that in addition to hydride forming internal standards, the signal variations caused by the changes in the main plasma conditions can be corrected by using aqueous internal standards introduced by solution nebulization. The accuracy of the measurements were studied by analyzing two different certified reference materials (ERM-CA615 and NIST 1573a) and the results were in good agreement with the certified values. However, it was found out, that the Bi was not suitable hydride forming internal standard for the real samples because it can occur in the samples in small concentrations and the formed hydride is instable.

Nanomaterial size distribution analysis via liquid nebulization coupled with ion mobility spectrometry (LN-IMS).

We apply liquid nebulization (LN) in series with ion mobility spectrometry (IMS, using a differential mobility analyzer coupled to a condensation particle counter) to measure the size distribution functions (the number concentration per unit log diameter) of gold nanospheres in the 5-30 nm range, 70 nm × 11.7 nm gold nanorods, and albumin proteins originally in aqueous suspensions. In prior studies, IMS measurements have only been carried out for colloidal nanoparticles in this size range using electrosprays for aerosolization, as traditional nebulizers produce supermicrometer droplets which leave residue particles from non-volatile species. Residue particles mask the size distribution of the particles of interest. Uniquely, the LN employed in this study uses both online dilution (with dilution factors of up to 10(4)) with ultra-high purity water and a ball-impactor to remove droplets larger than 500 nm in diameter. This combination enables hydrosol-to-aerosol conversion preserving the size and morphology of particles, and also enables higher non-volatile residue tolerance than electrospray based aerosolization. Through LN-IMS measurements we show that the size distribution functions of narrowly distributed but similarly sized particles can be distinguished from one another, which is not possible with Nanoparticle Tracking Analysis in the sub-30 nm size range. Through comparison to electron microscopy measurements, we find that the size distribution functions inferred via LN-IMS measurements correspond to the particle sizes coated by surfactants, i.e. as they persist in colloidal suspensions. Finally, we show that the gas phase particle concentrations inferred from IMS size distribution functions are functions of only of the liquid phase particle concentration, and are independent of particle size, shape, and chemical composition. Therefore LN-IMS enables characterization of the size, yield, and polydispersity of sub-30 nm particles.

Progress in Ultrasonic Spray Pyrolysis for Condensed Matter Sciences Developed From Ultrasonic Nebulization Theories Since Michael Faraday

This review outlines, in great detail, the history of the phenomenon of ultrasonic nebulization of liquids since the discovery of such an effect by Michael Faraday and the explanation of the phenomenon by capillary wave mechanism and “cavitation” hypothesis. Capillary waves described by the Kelvin equation are confirmed by Lang's experiment and more theoretical models by Peskin & Raco and Jokanovic. Cavitation bubbles have been elaborated by the Rayleigh-Plesset equation as well as the correlation equations between predicted and experimentally measured droplet diameter. Correlation equations such as one by Rajan & Pandit and Avvaru et al. have been considered. Ultrasonic spray pyrolysis for materials processing and the theories that predict the final particle size distribution are introduced. The popularity of the technique is shown by the rising number of research groups in the world processing various materials by this method due to its cost-effectiveness, purity of its products, and controllability of particle size as well as final properties.

A prototype of a new inductively coupled plasma time-of-flight mass spectrometer providing temporally resolved, multi-element detection of short signals generated by single particles and droplets

A prototype inductively coupled plasma time-of-flight mass spectrometer (ICPTOFMS) for time resolved measurements of transient signals in the microsecond regime is described in this work. Analytical figures of merit for the prototype are given for both liquid nebulization and single droplet introduction and are compared to a conventional quadrupole-based ICPMS using the same ICP source and vacuum interface. Quasi-simultaneous detection at a time resolution of 33 μs of the prototype ICPTOFMS allows multi-isotope monitoring of short signals (200–500 μs duration) generated from individual droplets and particles. The capabilities of the instrument for the analysis of single nanoparticles are studied using microdroplets consisting of a multi-element standard solution and containing 114 nm Au particles. The detection efficiencies for Ag and Au, calculated from the response of individual droplets and particles, are similar to those of the quadrupole-based instrument and amount to 1.3 × 10−6 ions per atom and 3.1 × 10−6 ions per atom, respectively. The sizes of the smallest detectable Ag, Au and U metallic nanoparticles are estimated to be 46 nm, 32 nm and 22 nm, respectively. Furthermore, time shifts of the signals of different elements within single droplets were observed. These new results demonstrate the advantage of the temporal resolution of the instrument for studying processes taking place in the plasma on the μs-time scale.

The use of a dual mode sample introduction system for internal standardization in the determination of Hg at the ng L−1 level by cold vapor ICP-MS

A dual mode sample introduction system was applied to simultaneous connection of cold vapor (CV) and liquid nebulization with ICP-MS. Gaseous mercury from a cold vapor system and liquid aerosol generated by pneumatic nebulization were transported into plasma via individual argon gas flow. The purpose of this configuration was to use aqueous internal standards for drift correction in low-level mercury analysis by CV-ICP-MS. Platinum, thallium and bismuth were studied as potential internal standards for mercury. The results indicated that each internal standard studied can be used to correct mercury signal instabilities during CV-ICP-MS analysis. The accuracy and precision of the results obtained using a dual mode system were confirmed by analyzing a certified reference material (ERM-CA615, groundwater). The internal standardization using a dual mode system was then applied to determine mercury concentrations in natural water samples. The results obtained for natural water samples using internal standards were in good agreement with those obtained by an isotope dilution CV-ICP-MS method, which could be considered as a reference method.

Low power cross-flow atmospheric pressure Ar + He plasma jet : Spectroscopic diagnostic and excitation capabilities

A cross-flow atmospheric plasma jet with distilled water or analyte solution nebulization has been investigated. The plasma gas flows perpendicularly to the RF powered electrode (11.21 MHz) and a grounded electrode was added for plasma stabilization. The working parameters of the plasma generator can be controlled in order to maximize either the plasma power (75 W) or the voltage on the RF powered electrode (plasma power, 40 W). The plasma gas, pure argon (0.4 l min − 1) or a mixture of argon (0.3–0.4 l min − 1) and helium (0–0.2 l min − 1), was also used for liquid nebulization. Optical emission of the plasma, collected in the normal viewing mode, was used for plasma diagnostics and for evaluating its excitation capabilities. The influence of helium content in the mixed-gas plasma on the plasma characteristics and on the emission axial profiles of the plasma gas constituents and of the analytes originate from the wet aerosol was studied. The addition of helium to the argon plasma, generally determines decreases in the emission of the plasma gas constituents (with the exception of molecular nitrogen), in the rotational temperature and in the electron number density and increases in the excitation temperatures and in the emission of easily excitable analytes. Based on the determined electron number densities, it was concluded that in the plasma zone which presents interest from analytical point of view the plasma is not very far from the partial thermodynamic equilibrium. In function of the helium content in the plasma gas and of the axial distance from the powered electrode the excitation temperatures are in the range of 2420–3340 K for argon, 2500–5450 K for oxygen and 900–2610 K for ionic calcium and the electron number densities are in the range of 1.2 10 12–1.25 10 13 cm − 3. Some elements with excitation energy lower than 6 eV were excited in the plasma. The plasma excitation capability depends on the working conditions of the plasma generator (maximum power or maximum voltage on the RF powered electrode) and on the helium content in the mixed-gas plasma. The estimated detection limits for the studied elements (Na, Li, K, Ca, Cu, Ag, Cd, Hg and Zn) are in the range of 7 ng ml − 1 to 28 μg ml − 1.

Assessment of the precision and accuracy of thorium (232Th) and uranium (238U) measured by quadrupole based inductively coupled plasma-mass spectrometry using liquid nebulization, nanosecond and femtosecond laser ablation

The precision and accuracy of the 238U/232Th ratio were evaluated from liquid nebulization and direct solid sampling repetitive pulsed laser ablation. Nanosecond and femtosecond pulsed lasers at 266 nm wavelength were utilized for the ablation studies. The ICP-MS and sampling parameters were optimized for each procedure; flow rates, gases, laser energy and other parameters were optimized for the particular sampling approach and therefore will not be the same. The work is not a comparison per se but represents performance metrics for three optimized sampling modalities. As expected, nanosecond pulsed ablation provided the greatest inaccuracy (>30%) from the nominal 238U/232Th bulk ratio. This deviation from bulk ratio is attributed to incomplete vaporization of large particle agglomerates produced by nanosecond laser ablation. Femtosecond pulsed ablation provided inaccuracy (∼1–3%) approaching that of liquid nebulization (∼1%). In terms of temporal relative standard deviation (TRSD) and relative standard deviation (RSD), liquid nebulization provided the best precision for the 238U/232Th ratio (TRSD ∼3–5%, RSD ∼0.2–0.6%), femtosecond laser ablation (TRSD ∼5–12%, RSD ∼1%) and nanosecond laser ablation (TRSD ∼25–48%, RSD ∼9–12%). Laser ablation requires less sample to achieve these performance metrics, in some cases less than a factor of 100-times depending on the entrainment and transport efficiency.

The lava lake-induced volcanic plume at Nyiragongo Volcano (DRC): Environmental effects on crop and population

Stable isotopes, such as C, N, O and S, are successfully used as classical environmental tracers. During the last few years, heavy stable isotopes are getting more and more attention as tracers and proxies in biogeochemical and environmental studies. Multicollector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS) has enabled scientists to obtain high precise isotopic analyses of heavy elements such as C1, Ca, Fe, Cu, Zn, Hg and Pb. These isotopic systems can be used as important tracers in studying metal contaminants, biomedical processes and pollution of aquatic environments. MC-ICPMS is a powerful technique for the isotopic analysis of most elements, with the exception of light elements such as H, C, N and O and noble gases. The advantage of the ICP source is that it can ionize all elements with very high sensitivity. Various inlet systems can be used to introduce samples into the mass spectrometer, for instance gas chromatography (GC), liquid chromatography (LC), laser ablation, or conventional liquid nebulization. The aerosol is transported by an Ar and/or He gas flow into the ICP source where it is effectively ionized and introduced into the mass analyzer through a differential pumping system. The variable multicollector detector array allows the user to adjust the detector positions along the focal plane of the mass spectrometer so that all isotopes of interest can be measured simultaneously. Molecular interferences as carbides, nitrides, oxides, argides or doubly-charged species can show up in the mass spectrum and interfere with the elemental isotope peaks. High mass resolution is needed to effectively discriminate against these interferences. The ion optics of the Finnigan NEPTUNE is specially designed to meet this requirement and expand the power of isotope ratio measurements even to elements where previously isobaric interferences were the limit. The presentation will discuss the applications of S, C1, Fe and Hg isotopes to study various processes linked to geochemistry and health using the Finnigan NEPTUNE.

Liquid Atomizing: Nebulizing and Other Methods of Producing Aerosols

Liquid atomization (or nebulization) is the most traditional method of drug delivery to the lung. Although other methods seem to often be preferred for the delivery of new drugs, nebulizers are experiencing a revival, with new devices based on different atomization techniques, and the more traditional jet nebulizers evolving to become "smart nebulizers." These smart devices synchronize delivery with the patient's breath, estimate or measure delivered dose, provide feedback and data storage, and in some cases control breathing maneuvers. Besides adding new features, new nebulizers are also addressing traditional shortcomings, namely, reducing size, bulkiness, and power consumption. But in the longer term, nebulizers are expected to offer even more important features. Following the trend toward individually optimized therapy, nebulizers will be able to estimate deposited dosage and concentrations in the lung. In addition, as progress in nanotechnology allows the development of smart drug carrying particles, advanced liquid nebulization is expected to be the delivery mode of choice for these smart particle aerosols.

Surfactant assisted chemical vapour generation of silver for AAS and ICP-OES: a mechanistic study

A chemical vapour generation (CVG) procedure for the production of volatile species of Ag was developed and studied using AAS and ICP-OES detection. A characteristic mass of 0.12 ng was achieved using a miniature diffusion flame atomizer-AAS system, whereas a 38-fold higher sensitivity (as cps per ng of introduced analyte) compared with conventional liquid nebulization was obtained with ICP-OES. The overall efficiency of introduction of Ag to the plasma was verified to be over 20%. More than one order of magnitude enhancement of efficiency was obtained by the addition of a surfactant (Triton X-100 in combination with an antifoaming agent), the effect of which, however, cannot be ascribed to the formation of organized media. Experiments concerning the mechanism of the CVG, transport and memory effect are discussed: Ag CVG is not a simple one-step process as is the case for CVG of selenium, but rather a two-step procedure. Transport properties of the volatile Ag species resemble more the transport of the liquid aerosol than a simple gaseous species such as H2Se. Possible alternatives concerning the identity of the volatile metal species are presented.

Investigation of Sr isotope ratios in prehistoric human bones and teeth using laser ablation ICP-MS and ICP-MS after Rb/Sr separation

87Sr/86Sr isotope ratio measurements on bone and teeth tissue were used in order to assess prehistoric human migration. Microstructural changes of skeletal remains caused by post mortem influences (especially dissolving and re-crystallization), may lead to erratic results, if invasive techniques (e.g. digestion and liquid nebulization ICP-MS) are used. Therefore, Rb/Sr separation performed on digested sample solutions prior to ICP-MS measurements was optimized and we developed a procedure to separate Sr from Rb quantitatively to enable a fast and reliable interference free measurement of Sr isotope ratios. As main goal, we have applied LA-ICP-MS on transversal bone cross sections on diagenetically altered and non-altered areas making use of both high lateral resolution and isotope ratio capabilities. Sr isotope ratio measurements on bone material were performed with an instrumental precision between 0.1 and 0.2% RSD by LA-ICP-MS. We could reveal mineralized phases (Brushit) histomorphologically within the cross section of cortical femur samples. Those crystallites showed a significantly increased amount of Rb. The results indicate that these products are exogenous. In addition, human teeth were analyzed for their 87Sr/86Sr isotope ratio primarily to investigate possible differences in enamel and dentine. LA-ICP-MS led to excellent results and shows RSD of isotope ratio measurements of about 0.1–0.2% on both enamel and dentine. One specific individual (from Neolithic Asparn/Schletz) was investigated using the prior methods and showed homogeneous Sr isotope ratios in dentine and bone, while the Sr isotopic composition in enamel was significantly different. This result demonstrates a possible migration of this individual during early childhood.

Laser Ablation Inductively Coupled Plasma Mass Spectrometry of Pressed Pellet Surrogates for Pu Materials Disposition

Successful Pu disposition by immobilization in glass or ceramic form requires accurate and precise knowledge of impurity amounts. Analysis of Pu material by conventional liquid nebulization requires dissolution, which is difficult due to the refractory nature of the samples. Laser ablation is a suitable sampling technique for direct analysis of solids. This paper demonstrates the procedures that were established for PuO2 analysis using laser ablation inductively coupled plasma mass spectrometer (ICP-MS). Pressed pellets prepared from CeO2 were used to simulate PuO2. Effects of laser conditions, sample preparation, and matrix composition, specifically mass of a matrix element and color, on the analyses of CeO2, Bi2O3, and PtO2 based pressed pellets were examined. Influence of mixing/grinding time on particle sizes, sample homogeneity, and ablation efficiency were investigated. Laser conditions that produce stoichiometric sampling were examined.

Micromechanical ultrasonic liquid nebulizer

A piezoelectric ZnO layer is used to set a thin silicon membrane into vibration. The possibility of applying this micromechanical structure for ultrasonic nebulization of liquids is studied. The dependence of the resulting drop distribution on membrane vibration frequency and liquid material parameters is compm'ed with the predictions of the capillary wave theory. Keywords: Micromechanics; Piezoelectricity; Ultrasonic nebulization.