Sliding spark spectroscopy — a new excitation source for generating atomic emission spectra for analysis

In this paper a newly developed technique, the so-called “Sliding Spark Spectrometry” is described. The method, with a comparatively simple system, allows direct in-situ analysis of handy, compact non-conductive material without prior sample preparation. A new excitation source for optical emission spectroscopy has been developed. The basic principle of the method is the thermal vaporization, ionization and excitation of a small amount of surface substrate using a train of high-current sliding sparks. The material components in the spark plasma are activated to emit radiation. From the atomic spectrum, informations about the composition and the element concentration in the sample can be obtained. With the use of the sliding spark spectrometer, a rapid analysis, especially of chlorine containing waste plastics and their inorganic additives can be carried out.     

Microwaves spark emission spectroscopy for the analysis of cations:A simple form of atomic emission spectroscopy

A novel method for the cation analysis was investigated.The analysis is based on the sparking of the salts of metals in a microwave oven after placing in a graphite cell.The graphite cell absorbs microwaves and produces high temperature which converts the salt into light emitting species.The colour of light was found to dependent on the nature of cation,however,the intensity of the emitted light was found to be depending upon the form and shape of the graphite assembly in addition to the concentration of the salt.This communication presents explanation for all these observations and for the systematic and quantitative analysis using microwave spark emission technique.     

Analysis of graphitized cast irons by optical emission spectroscopy: matrix effects in the glow discharge and the spark excitation

Graphite has a substantially lower sputtering rate in glow discharge than have the other structural components of graphitized cast irons, which leads to a structure-related matrix effect, consisting of an increasing relative surface coverage by graphite of the sample surface during the initial stage of the GD-OES analysis, and, consequently, to an increasing carbon signal intensity. This effect exists inherently in any multicomponent system with different sputtering rates of the components and should be taken into account in GD-OES quantification. A simple theory is presented to describe quantitatively the changes in relative contributions of different phases to the flux of the sputtered material entering the discharge and a formula is presented, expressing elemental intensity changes as a function of sputtering rates and stoichiometry of the structural components.After reaching the steady state, there are no substantial differences in the GD-OES signal response of the analyzed elements between the graphitic and the white cast irons. To reach this steady state, long preburn times and high sputtering rates have to be used. In the spark atomization/excitation, there are very strong and complex structure-related matrix effects, which make the analysis of graphitic cast irons by spark excitation impossible.     

The influence of intracellular storage material on bacterial identification by means of Raman spectroscopy

Previous studies dealing with bacterial identification by means of Raman spectroscopy have demonstrated that micro-Raman is a suitable technique for single-cell microbial identification. Raman spectra yield fingerprint-like information about all chemical components within one cell, and combined with multivariate methods, differentiation down to species or even strain level is possible. Many microorganisms may accumulate high amounts of polyhydroxyalkanoates (PHA) as carbon and energy storage materials within the cell and the Raman bands of PHA might impede the identification and differentiation of cells. To date, the identification by means of Raman spectroscopy have never been tested on bacteria which had accumulated PHA. Therefore, the aim of this study is to investigate the effect of intracellular polymer accumulation on the bacterial identification rate. Combining fluorescence imaging and Raman spectroscopy, we identified polyhydroxybutyrate (PHB) as a storage polymer accumulating in the investigated cells. The amount of energy storage material present within the cells was dependent on the physiological status of the microorganisms and strongly influenced the identification results. Bacteria in the stationary phase formed granules of crystalline PHB, which obstructed the Raman spectroscopic identification of bacterial species. The Raman spectra of bacteria in the exponential phase were dominated by signals from the storage material. However, the bands from proteins, lipids, and nucleic acids were not completely obscured by signals from PHB. Cells growing under either oxic or anoxic conditions could also be differentiated, suggesting that changes in Raman spectra can be interpreted as an indicator of different metabolic pathways. Although the presence of PHB induced severe changes in the Raman spectra, our results suggest that Raman spectroscopy can be successfully used for identification as long as the bacteria are not in the stationary phase.     

Influence of spark generator parameters in the analysis of graphite electrodes by spark source mass spectrometry

Spark source mass spectrometric analyses of doped carbon samples were performed at different pulse lengths, pulse frequencies and breakdown voltages. The pulse length and pulse frequencies had no influence on the analysis. The relation between breakdown voltage, spark gap and sample matrix was determined. With increasing breakdown voltage, the abundance of the multiply charged ions was found to decrease, whereas the abundance of the cluster ions increased. The breakdown voltage was also found to affect the absolute and relative intensities of different elements in different manners. Interpretation of these results led to some new considerations on the phenomena in a spark discharge.     

Software for automatic qualitative analysis and determination of elements by atomic emission spectroscopy with recognition of spectral interferences

This paper describes software for automatic qualitative and semi-quantitative analysis using inductively coupled plasma (ICP) atomic emission spectrometry with a high-resolution scanning monochromator. This software can be also used for automatic collection of wavelengths and intensities of spectral lines emitted from an ICP.     

Possibilities for correcting the influence of mineral acids and of drift in ICP emission spectral analysis

Summary Factorial design of the experiment has been applied to study the influence of HCl and H₂SO₄ on the analytical signal. The possibility of correcting this influence with the aid of the experimental equations obtained is indicated.A passive experiment was also carried out and the equations obtained were estimated by means of the methods of regression analysis, several response functions being studied. It is proved that minimal drift and maximal stability of regression coefficients are obtained when the ratio of net intensity of the line to the net intensity of the same line in a preliminarily chosen standard solution is accounted for. The stabilisation of regression coefficients makes it possible to prepare a flow chart to account for the influence of mineral acids and carrying out an ICP emission spectral analysis with a known acid content.

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Möglichkeiten zur Korrektur des Einflusses von Mineralsäuren und des Drift bei der ICP-Eimssionsspektralanalyse

Zusammenfassung Zur Untersuchung des Einflusses von HCl und H₂SO₄ auf das analytische Signal wurde die Faktoranalyse herangezogen. Die Möglichkeit der Korrektur dieses Einflusses mit Hilfe der erhaltenen experimentellen Gleichungen wird diskutiert. Auch ein passiver Versuch wurde durchgeführt, und die entsprechenden Gleichungen wurden durch Regressionsanalyse berechnet, wobei mehrere Response-Funktionen untersucht wurden. Minimaler Drift und maximale Stabilität der Regressionskoeffizienten werden erhalten, wenn man das Verhältnis der Nettolinienintensität in der Probe zu dem einer ausgewählten Standardlösung in Betracht zieht. Durch die Stabilisierung der Regressionskoeffizienten konnte ein Fließdiagramm aufgestellt werden, das den Einfluß von Mineralsäuren berücksichtigt.

     

Comparison of laser induced breakdown spectroscopy and spark induced breakdown spectroscopy for determination of mercury in soils

Mercury is a toxic element found throughout the environment. Elevated concentrations of mercury in soils are quite hazardous to plants growing in these soils and also the runoff of soils to nearby water bodies contaminates the water, endangering the flora and fauna of that region. This makes continuous monitoring of mercury very essential. This work compares two potential spectroscopic methods (laser induced breakdown spectroscopy (LIBS) and spark induced breakdown spectroscopy (SIBS)) at their optimum experimental conditions for mercury monitoring. For LIBS, pellets were prepared from soil samples of known concentration for generating a calibration curve while for SIBS, soil samples of known concentration were used in the powder form. The limits of detection (LODs) of Hg in soil were calculated from the Hg calibration curves. The LOD for mercury in soil calculated using LIBS and SIBS is 483 ppm and 20 ppm, respectively. The detection range for LIBS and SIBS is discussed.     

Matrix effects and analysis of biological material by spark source mass spectrometry

Summary Spark-source mass spectrometric analyses of synthetic simulated biological samples were performed to determine the importance of matrix effects. A correlation between the variation of the relative sensitivity coefficients (RSC's) and the spark plasma composition, hence plasma temperature, was found. The determined RSC's were used in the analysis of four biological standard reference materials. An accuracy of 10–13% and detection limits between 0.005 and 0.5 ppm were obtained during analysis under normal conditions.

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Matrixeffekte und Analyse von biologischem Material mit Hilfe der Funkenionen-Massenspektrometrie

Zusammenfassung Um die Bedeutung von Matrixeffekten zu untersuchen, wurden Analysen von synthetischem biologischem Material mit der Funkenquellen-Massenspektrometrie durchgeführt. Dabei wurde eine Beziehung zwischen der Veränderung der relativen Empfindlichkeitskoeffizienten und der Zusammensetzung des Funkenplasmas (und damit der Plasmatemperatur) festgestellt. Die bestimmten Empfindlichkeitskoeffizienten wurden zur Analyse von vier biologischen Standardreferenzmaterialien eingesetzt. Unter normalen Bedingungen wurde eine Genauigkeit von 10–13% und Nachweisgrenzen zwischen 0,005 und 0,5 ppm erreicht.

     

Multicolor single-molecule spectroscopy with alternating laser excitation for the investigation of interactions and dynamics

We have developed confocal multicolor single-molecule spectroscopy with optimized detection sensitivity on three spectrally distinct channels for the study of biomolecular interactions and FRET between more than two molecules. Using programmable acousto-optical devices as beamsplitter and excitation filter, we overcome some of the limitations of conventional multichroic beamsplitters and implement rapid alternation between three laser lines. This enables to visualize the synthesis of DNA three-way junctions on a single-molecule basis and to resolve seven stoichiometric subpopulations as well as to quantify FRET in the presence of competing energy transfer pathways. Furthermore, the ability to study correlated molecular movements by monitoring several distances within a biomolecular complex simultaneously is demonstrated.     

Total analysis of plant material and biological tissue by spark source mass spectrometry

Summary Analysis of biological material by spark source mass spectrometry is reported. Preliminary studies mainly based upon the analysis of the NBS standard reference material SRM-1571 (Orchard Leaves) are described. Attention is drawn to the importance of a suitable sample preparation method. The advantages of a wet digestion technique in a Teflon bomb are discussed and its use is justified by the satisfactory overall analysis precision of about 20%.

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Gesamtanalyse von Pflanzenmaterial und biologischem Gewebe mittels Funken-Massenspektrometrie

Zusammenfassung Die Analyse von biologischem Material mit der Funken-Massenspektrometrie wird beschrieben. Erste Untersuchungen basieren auf der Analyse der NBS-Standardprobe Orchard Leaves (NBS SRM-1571). Die Wichtigkeit einer geeigneten Probenvorbereitung wird betont. Die Vorteile der Naßaufschlußtechnik in einer Teflonbombe werden diskutiert und ihr Einsatz durch die gute Gesamtreproduzierbarkeit von etwa 20% gerechtfertigt.

     

The dye laser induced flourescence excitation and emission spectrum of the KXe molecule

Several new KXe bands have been observed between 400 and 540 rim. The striking differences between the fluorescence excitation spectrum and the emission spectrum excited at 404.4 nm give information on the potential curves involved.     

Experimental evidence for the curve crossing mechanism for collisional excitation in keV N2+*/He collisions by emission spectroscopy

Collision-induced emission (CIE) experiments were carried out by coupling a spectrograph and charge-coupled device detector (CCD) to a commercial analytical mass spectrometer. An Einzel lens and a deceleration-reacceleration lens assembly as described in the current article were installed in the mass spectrometer to allow for the deceleration of the ions before collision. Collision-induced emission spectra of N2+*/He collisions at lab frame collision energies from 2 to 8 keV were obtained from 190-1020 nm. The emissions were assigned to the Deltav=+2, +1, 0, -1, -2 vibrational transition progression in the N2+* B 2Sigmau+-->X 2Sigmag+ electronic transition as well as some atomic lines from the fragments N+, N* and the target gas He. N2+* A 2u-->X 2Sigmag+ emission was also observed but was very weak due to the long lifetime of the A 2u state. The relative intensities of the N2+*, N, and N+ emissions are independent of the ion translational energy within the studied energy range. This observation supports the curve-crossing mechanism for collisional excitation, suggesting that a complicated sequence of curve-crossings takes place upon collisional activation.     

UV spectra and excitation delocalization in DNA: influence of the spectral width.

The singlet excited states of the model DNA duplex (dA)10.(dT)10 are studied. Calculations are performed in the exciton theory framework. Molecular dynamics calculations provide the duplex geometry. The dipolar coupling is determined using atomic transition charges. The monomer transition energies are simulated by Gaussian functions resembling the absorption bands of nucleosides in aqueous solutions. Most of the excited states are found to be delocalized over at least two bases and result from the mixing of different monomer states. Their properties are only weakly affected by conformational changes of the double helix. On average, the highest oscillator strength is carried by the upper eigenstates. The duplex absorption spectra are shifted a few nanometers to higher energies with respect to the spectra of noninteracting monomers. The states with larger spatial extent are located close to the maximum of the absorption spectrum.     

Optical emission spectroscopy and modeling of plasma produced by laser ablation of titanium oxides

In the present study, the time evolution of electron number density, of electron, atom and ion temperatures, of plasma produced by KrF excimer laser ablation of titanium dioxide and monoxide targets, are investigated by temporally and spatially resolved optical emission spectroscopy over a wide range of laser fluence from 1.7 to 6 J cm⁻², oxygen pressures of 10⁻²–10⁻¹ torr and in a vacuum. A state-to-state collisional radiative model is proposed for the first time to interpret the experimental results at a distance of 0.6 mm from the target surface, in vacuum and for a time delay from 100 to 300 ns from the beginning of the laser pulse. In particular, we concentrate our attention on problems concerning the existence of the local thermodynamic conditions in the laser-induced plasma and deviation from them, as observed in our experiment. The numerical model proposed for calculating the electron number density and the population densities of atoms and ions in excited states give good quantitative agreement with the experimental results of the optical emission spectroscopy measurements.     

On the influence of surfactants on the adsorption of polysaccharide-based polymers on cotton studied by means of fluorescence spectroscopy

In this study, we examined the influence of surfactants on the adsorption of polymers on cotton fibers. The extent of polymer adsorption on cotton was determined directly by means of fluorescence spectroscopy using fluorescently labeled polymers. The investigation of polymer adsorption in the presence of different types of surfactants and for a large range of differently structured polymers allows us to obtain a rather general picture of this important issue. Systematic relationships between the presence of surfactant and the type of polymer can be deduced but cannot be cast in simple terms such as electrostatic interaction but instead depend on the detailed interaction between the surfactant and polymer both in solution and adsorbed on the cotton surface. A particularly complex situation arises for the case of oppositely charged surfactant and polymer because of the possibility of precipitate formation. The study of such complex systems not only is of scientific interest but also is of great commercial interest because both polymers and surfactants are parts of detergent formulations and cotton is one of the most abundantly used materials for fabrics.