Israel Schechter

Publications of Israel Schechter

• Quantification of trace metals in water using complexation and filter concentration.

  Authors: Bella Dolgin, Valery Bulatov, Julia Japarov, Eyal Elish, Elad Edri, Israel Schechter

  Talanta. 06/2010; 81(4-5):1482-8.

  Various metals undergo complexation with organic reagents, resulting in colored products. In practice, their molar absorptivities allow for quantification in the ppm range. However, a properVarious metals undergo complexation with organic reagents, resulting in colored products. In practice, their molar absorptivities allow for quantification in the ppm range. However, a proper pre-concentration of the colored complex on paper filter lowers the quantification limit to the low ppb range. In this study, several pre-concentration techniques have been examined and compared: filtering the already complexed mixture, complexation on filter, and dipping of dye-covered filter in solution. The best quantification has been based on the ratio of filter reflectance at a certain wavelength to that at zero metal concentration. The studied complex formations (Ni ions with TAN and Cd ions with PAN) involve production of nanoparticle suspensions, which are associated with complicated kinetics. The kinetics of the complexation of Ni ions with TAN has been investigated and optimum timing could be found. Kinetic optimization in regard to some interferences has also been suggested.

• Multiphoton ionization spectroscopy as a diagnostic technique of surfaces under ambient conditions.

  Authors: Yuheng Chen, Valery Bulatov, Natalia Vinerot, Israel Schechter

  Analytical chemistry. 04/2010; 82(9):3454-6.

  Direct detection of solid substances is an important yet challenging issue in analytical chemistry. Laser multiphoton ionization spectroscopy has been applied for the first time for direct analysisDirect detection of solid substances is an important yet challenging issue in analytical chemistry. Laser multiphoton ionization spectroscopy has been applied for the first time for direct analysis of solids under ambient conditions. In this method, a solid powder/film is placed on a conductive surface and is irradiated by a pulsed tunable laser while an electrical field of approximately 2 kV cm(-1) is applied across this conductive surface and another electrode. The resulting photoelectrons and negative ions are measured by recording the current as a function of wavelength to produce a multiphoton ionization spectrum that is characteristic of the surface. Results indicate rich spectral features that can be used for compound identification. The present sensitivity is in the low picomole range. This method has been successfully tested for direct detection of various organic molecules, including explosives, narcotic drugs, and polycyclic aromatic compounds.

• Application of synchronous fluorescence to parchment characterization.

  Authors: Bella Dolgin, Valery Bulatov, Israel Schechter

  Analytical and bioanalytical chemistry. 09/2009;

  A nondestructive method for quantitative parchment characterization and sensitive indication of its deterioration stage was developed. Synchronous fluorescence (SF) measurements were applied for theA nondestructive method for quantitative parchment characterization and sensitive indication of its deterioration stage was developed. Synchronous fluorescence (SF) measurements were applied for the first time to parchment samples. The method provides detailed spectral features, which are useful for parchment characterization. The discrimination of parchment samples into groups (modern, historical, and artificially aged) was successfully performed. The SF spectra could be resolved into specific fluorophores, which were related to the parchment condition. The spectral data indicate a continuous change in the collagen-to-gelatin ratio during the aging process. Depth-resolved synchronous fluorescence spectra were also measured. The data indicate that parchments possess a layered structure, and the dominant fluorophore in the upper layer is different from those in the lower layers. Layer-resolved profiling allows for quantifying the contribution of each fluorophore in each given layer. This way, significant differences between modern, artificially aged, and historical samples can be observed.

• Non-destructive assessment of parchment deterioration by optical methods.

  Authors: Bella Dolgin, Valery Bulatov, Israel Schechter

  Analytical and bioanalytical chemistry. 09/2007; 388(8):1885-96.

  A non-destructive and non-invasive method for quantitative characterization of parchment deterioration, based on spectral measurements, is proposed. Deterioration due to both natural aging (ancientA non-destructive and non-invasive method for quantitative characterization of parchment deterioration, based on spectral measurements, is proposed. Deterioration due to both natural aging (ancient parchments) and artificial aging (achieved by means of controlled UV irradiation and temperature treatment) was investigated. The effect of aging on parchment native fluorescence was correlated with its deterioration condition. Aging causes fluorescence intensity drop, spectral shift of the main peak, and an overall change in the fluorescence spectral features. Digital color imaging analysis based on visible reflectance from the parchment surface was also applied, and the correspondent color components (RGB) were successively correlated with the state of parchment deterioration/aging. The fluorescence and color imaging data were validated by analysis of historical parchments, aged between 50 and 2000 years and covering a large variety of states of deterioration. The samples were independently assessed by traditional microscopy methods. We conclude that the proposed optical method qualifies well as a non-destructive tool for rapid assessment of the stage of parchment deterioration.

• Use of LIBS for rapid characterization of parchment.

  Authors: Bella Dolgin, Yuheng Chen, Valery Bulatov, Israel Schechter

  Analytical and bioanalytical chemistry. 12/2006; 386(5):1535-41.

  Parchment from different sources has been analyzed by laser-induced breakdown spectroscopy (LIBS) for determination of Ca, Na, K, Mg, Fe, Cu, and Mn. The LIBS results were compared with results fromParchment from different sources has been analyzed by laser-induced breakdown spectroscopy (LIBS) for determination of Ca, Na, K, Mg, Fe, Cu, and Mn. The LIBS results were compared with results from inductively coupled plasma spectroscopy (ICP) and good correlation was obtained. Rapid distinction between modern and historical samples was achieved by discriminant analysis of the LIBS data. Animal type recognition was also possible on the basis of Mg/Cu emission peak ratio and Mg depth profiling.

• Enhanced electro-catalytic degradation of chloroorganic compounds in the presence of ultrasound.

  Authors: Yakov Yasman, Valery Bulatov, Irene Rabin, Marcello Binetti, Israel Schechter

  Ultrasonics sonochemistry. 05/2006; 13(3):271-7.

  The application of finely divided (black) Pd and Pd-Fe powder in the sono-electro-catalytic reduction of chlorophenoxy herbicides (2,4-D) and chlorophenols (2,4-DCP) in aqueous solutions allows forThe application of finely divided (black) Pd and Pd-Fe powder in the sono-electro-catalytic reduction of chlorophenoxy herbicides (2,4-D) and chlorophenols (2,4-DCP) in aqueous solutions allows for effective destruction of toxic chlorinated aromatic compounds. At 20 degrees C complete conversion of these compounds is observed within 10 min. On bimetallic Pd/Fe catalyst, intermediates due to the oxidation reaction are detected in addition to the products of dechlorination. The bimetallic catalyst appears to be energetically and economically superior to the Pd. In both cases, the reaction times were considerably shortened in comparison with traditional electro-catalytic processes.

• Absorption and scattering characterization of airborne microparticulates by a cavity ringdown technique.

  Authors: Valery Bulatov, Yuheng Chen, Aktam Khalmanov, Israel Schechter

  Analytical and bioanalytical chemistry. 02/2006; 384(1):155-60.

  Nonresonant cavity ringdown laser absorption spectroscopy (CRLAS) was applied for detection and characterization of airborne particulates. Sensitive detection of a variety of aerosols under ambientNonresonant cavity ringdown laser absorption spectroscopy (CRLAS) was applied for detection and characterization of airborne particulates. Sensitive detection of a variety of aerosols under ambient conditions was achieved. The method provides, for the first time, time-resolved absolute aerosol concentration, with spatial resolution (along a line). The first report on absorption spectroscopy of monodispersed aerosols (in the size range 100-200 nm) is provided, and comparisons are made with the bulk data. The results indicate the possibility of applying CRLAS for selective analysis of aerosols. A new method for estimating the aerosol refraction index is also obtained from the ringdown data.

• Mapping and elemental fractionation of aerosols generated by laser-induced breakdown ablation.

  Authors: Yuheng Chen, Valery Bulatov, Liviu Singer, Josef Stricker, Israel Schechter

  Analytical and bioanalytical chemistry. 01/2006; 383(7-8):1090-7.

  Laser-induced breakdown spectroscopy (LIBS) has been used to map the distribution of particulate matter inside the plume created by laser ablation of a brass target. The spatial density distributionLaser-induced breakdown spectroscopy (LIBS) has been used to map the distribution of particulate matter inside the plume created by laser ablation of a brass target. The spatial density distribution of the different components of the plume was determined in an attempt to reveal the mechanism of fractionation in the process of the laser ablation. In this experiment two Nd:YAG pulsed lasers were used. The first beam was focused on the target to generate a plume after breakdown of the surface. The second laser was focused on the plume and generated the second breakdown. The composition of the region probed by the second beam was determined by analyzing the spectral emission from the second breakdown. By scanning the probe time and position, the temporal and spatial evolution of the laser ablative plume could be discovered. Spatial and temporal fractionation was observed in brass plume.

• Detector for particulate polycyclic aromatic hydrocarbons in water.

  Authors: Jane Levinson, Chanan Sluszny, Yakov Yasman, Valery Bulatov, Israel Schechter

  Analytical and bioanalytical chemistry. 05/2005; 381(8):1584-91.

  It is estimated that most polycyclic aromatic hydrocarbons (PAHs) in environmental water are not dissolved but rather in particulate form. Nevertheless, the currently available optical detectors areIt is estimated that most polycyclic aromatic hydrocarbons (PAHs) in environmental water are not dissolved but rather in particulate form. Nevertheless, the currently available optical detectors are not suited for proper sampling of solid PAHs. A new setup for direct sampling and quantification of suspended particulate PAHs in water is suggested. It is based on a polymeric film that has the capability of dissolving PAH particulates, coupled to a traditional laser-induced fluorescence probe. Kinetics and performance of two sampling modes have been studied: bulk sampling, by immersing the probe into the water, and surface sampling, by laying the film on the water surface. The latter method has proved to be more sensitive; however, it is diffusion-limited. Linear calibration plots have provided quantification over a wide concentration range with detection limits in the ppb range (these could be improved by using a modified probe). The effects due to other particulates in water have been studied and only little interferences have been observed. The possibility of analysis of PAH mixtures has been addressed and it has been concluded that multivariate analysis is needed.

• A new sono-electrochemical method for enhanced detoxification of hydrophilic chloroorganic pollutants in water.

  Authors: Yakov Yasman, Valery Bulatov, Vladimir V Gridin, Sabina Agur, Noah Galil, Robert Armon, Israel Schechter

  Ultrasonics sonochemistry. 10/2004; 11(6):365-72.

  A new method for detoxification of hydrophilic chloroorganic pollutants in effluent water was developed, using a combination of ultrasound waves, electrochemistry and Fenton's reagent. The advantagesA new method for detoxification of hydrophilic chloroorganic pollutants in effluent water was developed, using a combination of ultrasound waves, electrochemistry and Fenton's reagent. The advantages of the method are exemplified using two target compounds: the common herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) and its derivative 2,4-dichlorophenol (2,4-DCP). The high degradation power of this process is due to the large production of oxidizing hydroxyl radicals and high mass transfer due to sonication. Application of this sono-electrochemical Fenton process (SEF) treatment (at 20 kHz) with quite a small current density, accomplished almost 50% oxidation of 2,4-D solution (300 ppm, 1.2 mM) in just 60 s. Similar treatments ran for 600 s resulted in practically full degradation of the herbicide; sizable oxidation of 2,4-DCP also occurs. The main intermediate compounds produced in the SEF process were identified. Their kinetic profile was measured and a chemical reaction scheme was suggested. The efficiency of the SEF process is tentatively much higher than the reference degradation methods and the time required for full degradation is considerably shorter. The SEF process maintains high performance up to concentrations which are higher than reference methods. The optimum concentration of Fe2+ ions required for this process was found to be of about 2 mM, which is lower than that in reference techniques. These findings indicate that SEF process may be an effective method for detoxification of environmental water.

• Study of the morphology of a laser-produced aerosol plume by cavity ringdown laser absorption spectroscopy.

  Authors: Valery Bulatov, Aktam Khalmanov, Israel Schechter

  Analytical and bioanalytical chemistry. 05/2003; 375(8):1282-6.

  Cavity ring-down laser absorption spectroscopy (CRLAS) was applied for the first time to detection and characterization of laser breakdown generated aerosols. The method provided time-resolvedCavity ring-down laser absorption spectroscopy (CRLAS) was applied for the first time to detection and characterization of laser breakdown generated aerosols. The method provided time-resolved morphological information on the aerosol plume, which is of importance in laser ablation (LA) and deposition, in laser-induced breakdown spectroscopy (LIBS) analysis, and in laser ablation inductively coupled plasma (LA-ICP) methods. This method provides sensitive detection of a variety of aerosols produced under ambient conditions. The morphological investigation revealed that the aerosol density has a reproducible pattern as a function of distance from the surface, although its details depend on time, on geometrical parameters and on the surface characteristics.

• Combined micro-droplet and thin-film-assisted pre-concentration of lead traces for on-line monitoring using anodic stripping voltammetry.

  Authors: Inessa Belostotsky, Vladimir V Gridin, Israel Schechter, Chaim N Yarnitzky

  Analytical and bioanalytical chemistry. 03/2003; 375(4):482-8.

  An improved analytical method for airborne lead traces is reported. It is based on using a Venturi scrubber sampling device for simultaneous thin-film stripping and droplet entrapment of aerosolAn improved analytical method for airborne lead traces is reported. It is based on using a Venturi scrubber sampling device for simultaneous thin-film stripping and droplet entrapment of aerosol influxes. At least threefold enhancement of the lead-trace pre-concentration is achieved. The sampled traces are analyzed by square-wave anodic stripping voltammetry. The method was tested by a series of pilot experiments. These were performed using contaminant-controlled air intakes. Reproducible calibration plots were obtained. The data were validated by traditional analysis using filter sampling. LODs are comparable with the conventional techniques. The method was successfully applied to on-line and in situ environmental monitoring of lead.

• On-line remote prediction of gasoline properties by combined optical methods

  Authors: Iris Litani-Barzilai, Ilan Sela, Valery Bulatov, Irena Zilberman, Israel Schechter

  Analytica Chimica Acta.

  On-line prediction of 10 gasoline properties, such as research and motor octane numbers, vapor pressure, API gravity, aromatic contents, etc., are carried out on-line by a remotely operated detectorOn-line prediction of 10 gasoline properties, such as research and motor octane numbers, vapor pressure, API gravity, aromatic contents, etc., are carried out on-line by a remotely operated detector coupled to the main control unit by communication optical fibers. This information is of considerable importance since it is needed for process monitoring and for the preparation of final petrochemical products of well defined properties. The currently available spectroscopic methods for predicting gasoline properties, which are based on near infrared (NIR) (and recently on Fourier transform infrared (FTIR) spectrometry) coupled with chemometric algorithms, provide limited performance (e.g. 0.4 standard error of prediction (SEP), for octane number). We propose an improvement of the performance by applying combined optical methods. In this study we combine on-line information from a short-wave NIR photodiode array spectrometer (700–1000 nm) with laser induced fluorescence (LIF) spectra obtained with a PC-plugged in linear CCD spectrometer. UV excitation is performed by harmonics of a compact and low-cost Nd:YAG laser, and the system is remotely operated through optical fibers. A comparison between the octane number predictions by NIR spectrometry and by LIF from third and fourth harmonics, is provided. It is shown that the addition of the fluorescence information improves octane number prediction (<0.2 SEP). These two setups (NIR and LIF) can be combined into one integrated system, based on common optical fibers and detector.

• Non-aqueous-phase-liquid breakthrough during evaporative drying of clay barriers

  Authors: Dorit Matmon, Vladimir V Gridin, Jacob Bear, Sam Frydman, Israel Schechter

  Journal of Contaminant Hydrology.

  In this study, an attempt has been made to model a real field scenario, whereby an initially almost saturated clay liner in a waste site is gradually drying, due to evaporation at its lower boundary.In this study, an attempt has been made to model a real field scenario, whereby an initially almost saturated clay liner in a waste site is gradually drying, due to evaporation at its lower boundary. A detailed conceptual model that deals with the penetration and breakthrough of non-aqueous-phase-liquid (NAPL) in clay liners is introduced. Water content of clay samples was monitored during ambient evaporation through apertures at the base of sample holders. Clay drying rate served as the primary parameter for the NAPL breakthrough study. The interconnection between drying rates, structural damage formation (cracks and suction) and NAPL penetration is especially addressed. The processes taking place in the clay samples during drying appear to be associated with the capillary effects between the different fluid phases in the vicinity of either the NAPL–clay or the clay–air boundaries. A conceptual model of NAPL penetration and breakthrough of the clay layer has been considered, based on both indirect and direct observations of structural damages produced on either clay boundaries. A mutual interaction between these two boundaries is suggested and discussed. NAPL breakthrough is suggested to take place through cracks initiated on the upper soil surface.

• Venturi-scrubber pre-concentration technique for electrochemical detection of airborne lead traces

  Authors: Inessa Belostotsky, Vladimir V. Gridin, Israel Schechter, Chaim N. Yarnitzky

  Analytica Chimica Acta.

  A method for ambient tracing of airborne lead-containing pollutants is reported. It is based on coupling a Venturi-scrubber aerosol sampling with square-wave anodic stripping voltammetry. The methodA method for ambient tracing of airborne lead-containing pollutants is reported. It is based on coupling a Venturi-scrubber aerosol sampling with square-wave anodic stripping voltammetry. The method was tested by a series of pilot experiments. These were performed using contamination-controlled air intakes. A linear concentration process was achieved by the Venturi-scrubber. These data were cross-referenced by means of standard analysis of the lead-containing aerosols entrapped on filter sampler. Successful modeling of experimental results was achieved. Several aspects, relevant to on-line monitoring of such lead-contaminated aerosols, have been addressed. The sampling efficiency increases with the average aerosol size and is reduced by persisting non-soluble airborne particulates. The reported pre-concentration processes are consistent with a well-known inertial impact mechanism. In regards of capturing liquid aerosols, this approach appears to be more effective than that with filters.

• Classification and quantification of polycyclic aromatic hydrocarbons on quartz sand particles by direct Fourier transform imaging fluorescence

  Authors: Chanan Sluszny, Valery Bulatov, Israel Schechter

  Analytica Chimica Acta.

  A new method for analysis of PAH contamination deposited on quartz sand was developed. It is based on direct observation of the UV-induced fluorescence using a microscope and a specially designedA new method for analysis of PAH contamination deposited on quartz sand was developed. It is based on direct observation of the UV-induced fluorescence using a microscope and a specially designed imaging spectrometer which provides full fluorescence spectra at each pixel. The method is fast and requires no sample preparation. Linear calibration plots were obtained for monocomponent contaminations and for simple PAH mixtures. Absolute detection limits of a few pg are reported, which correspond to bulk concentrations in the μg g−1 range. In addition to concentrations, the method provides microscopic chemical images of the contaminants, which may provide useful source characterization.

• Polymer film sensor for sampling and remote analysis of polycyclic aromatic hydrocarbons in clear and turbid aqueous environments

  Authors: Chanan Sluszny, Vladimir V. Gridin, Valery Bulatov, Israel Schechter

  Analytica Chimica Acta.

  A sensor for remote analysis of polycyclic aromatic hydrocarbons (PAHs) has been developed. It is based on direct solid phase extraction of the pollutants on a polymeric film, followed by monitoringA sensor for remote analysis of polycyclic aromatic hydrocarbons (PAHs) has been developed. It is based on direct solid phase extraction of the pollutants on a polymeric film, followed by monitoring the laser induced fluorescence, emitted from the film, via optical fibers. The proposed sensor has been applied to direct PAH analysis in clear and turbid aqueous environments. Linear calibration plots have been obtained for PAH solutions containing both humic substances and clay suspensions. Detection limits in the range of 10 ppt have been achieved. Results are obtained almost instantaneously (in drinking water) or within minutes, in more complicated matrices. This set-up has provided considerable improvement of the detection limits, when compared to the traditional fiber-optic fluorescence probe. In case of pyrene, a 100-fold and a 250-fold improvement in the detection limits have been obtained for the clay and humic substances-containing water, respectively. The spectral response of the polymeric film has been studied under various conditions and the feasibility of the method for analysis of PAH mixtures has been addressed.

• Study of matrix effects in laser plasma spectroscopy by shock wave propagation

  Authors: Rivie Krasniker, Valery Bulatov, Israel Schechter

  Spectrochimica Acta Part B: Atomic Spectroscopy.

  The origin of analytical matrix effects in laser plasma spectroscopy was investigated. We focused on matrix effects in sand/soil mixtures and attempted to explain the increase in the spectralThe origin of analytical matrix effects in laser plasma spectroscopy was investigated. We focused on matrix effects in sand/soil mixtures and attempted to explain the increase in the spectral response of trace elements (at constant concentration) with sand percentage. First, it was found that the energy coupled in the plasma, and which can be calculated from the propagation of the laser induced shock wave, indeed characterizes the matrix. A simple experimental setup for such measurements was suggested. Our results indicate that previous explanations of the matrix effects in this system may not be correct. We suggested that the main matrix effects were attributed to the depth of the laser-induced crater, which was correlated to a portion of the laser energy that penetrates into sand particulates and does not cause direct ablation. This explanation holds when no other effects are present (e.g. grain size distribution). The hypothesis was validated by experimental data.

• Aerosol analysis by cavity-ring-down laser spectroscopy

  Authors: Valery Bulatov, Michal Fisher, Israel Schechter

  Analytica Chimica Acta.

  The cavity-ring-down technique was applied for aerosol detection. The experimental set-up was based on a pulsed dye laser pumped with the third harmonic of an Nd:YAG laser. Validation of the methodThe cavity-ring-down technique was applied for aerosol detection. The experimental set-up was based on a pulsed dye laser pumped with the third harmonic of an Nd:YAG laser. Validation of the method was performed using calibrated aerosol flows, all under ambient conditions. The method was exemplified with non-absorbing aerosols, such as NaCl and CuCl2·2H2O, of various sizes and concentrations. The results were used for the evaluation of the corresponding aerosol extinction coefficients as a function of size, shape and index of refraction. The thus obtained aerosol extinction efficiencies were compared to theoretical models. Good agreement with theory was observed for NaCl aerosols, while the results for CuCl2·2H2O particulates required averaging over particle size and over the orientation dependent index of refraction. The actual sensitivity currently achieved was as low as an extinction coefficient of 8×10−8 cm−1, which means detection capability of about six water micro-particulates per cm3. The ultimate theoretical performance of this method for aerosol detection was estimated as an extinction coefficient of 1.4×10−12 cm−1, corresponding to about 100 micro-particulates per m3. These figures indicate that this method has the potential to become one of the most sensitive on-line analytical technique for aerosol detection and quantification.

• Application of pulsed laser methods to in situ probing of highway originated pollutants

  Authors: Valery Bulatov, Vladimir V. Gridin, Felix Polyak, Israel Schechter

  Analytica Chimica Acta.

  A possibility of a portable field kit for studying traffic originated pollutants based on laser induced fluorescence (LIF) or multi-photon ionization fast-conductivity (MPI-FC) has been addressed.A possibility of a portable field kit for studying traffic originated pollutants based on laser induced fluorescence (LIF) or multi-photon ionization fast-conductivity (MPI-FC) has been addressed. The resulting instrumentation has been successfully tested on soil samples that were collected and classified according to their radial distance, R, from a busy highway. The sampling was done in the near-field range with R varying from 3 to 50 m. Organic material from the samples was transferred into hexane solutions by short-time shaking with pure hexane. These solutions were investigated by simple LIF and MPI-FC instruments, which can be engineered as portable units (e.g., a PC plugged-in spectrometer has been used, in which case both the signal excitation and detection were accessed by means of optical fibers). Detected traces showed a nearly fall-off of the LIF and MPI-FC experimental data as a function of the sample distance from the road. It is estimated that at 50 m from the road the contamination concentrations (about 90% aliphatics and 10% aromatics) are as high as 0.1 μg g−1. Both proposed methods provide good sensitivity at the relevant concentration range and may be applied for fast screening of traffic contamination of soils.