M.A. Harith

Panoramic laser-induced breakdown spectrometry of water

Wide spectral range time resolved laser-induced breakdown spectroscopy has been investigated to evaluate its potential for simultaneous determination of major, minor and trace concentrations in water. A combination of echelle spectrometry with a time gated intensified charge coupled device camera (ICCD) facilitated such working conditions. Multi-elemental panoramic line spectra (200-1000 nm) have been analyzed at different delay times t (0.2-10 ms) d and gate widths t (1-10 ms). The evolved laser-induced plasma in water has been followed up temporarily and w spatially. The behavior of the obtained curves is found to be, in general, analyte-dependent. Other physical parameters such as plasma temperature T and electron density N are determined from the spectra obtained under the optimized ee experimental conditions. Aqueous Na and Mg solutions of different concentrations were used to construct calibration curves and estimate the limit of detection (LOD) of the measurements. Other calibration curves for each of the two elements in mixed solutions are used to evaluate the matrix effect on the LOD. In all cases the calibration curves showed good linearity within two orders of magnitude. The lowest detection limits (1 and 2 m gm l ) are obtained y1 for Mg and Na in pure solutions, respectively, while slightly higher LOD values (1.2 and 2.5 m gm l ) are determined y1 for the same elements in the mixed solution. To assess the accuracy of such panoramic LIBS measurements, Mg and Na concentrations in bottled potable water have been determined and good agreement between the measured and labeled values is obtained. 2002 Published by Elsevier Science B.V.

LIBS limit of detection and plasma parameters of some elements in two different metallic matrices

In the present work a detailed study has been performed on the effect of the matrix on the limit of detection (LOD) and the plasma parameters of the laser induced breakdown spectroscopy (LIBS) technique. The LOD of magnesium, silicon, manganese and copper as minor elements was evaluated in aluminium standard sample alloys compared to the values of the LOD of the same elements in standard steel alloys. The effect of changing the matrix on the laser induced plasma plume parameters, namely the plasma temperature Te and the electron density Ne, has been also studied. Calibrations were achieved for the four elements with linear regression coefficients between 98–99% on average. According to the obtained results Mn and Cu have the lowest LOD in the steel alloy matrix, while Mg has much lower LOD in the aluminium alloy matrix. These results may be interpreted in view of the compatibility of the physical properties of the elements existing in the same matrix. Approximately similar electronic structure and values of melting point, density, atomic weight, etc., may facilitate better conditions for energy transfer within the matrix. From the application view point, it is possible for LIBS in the on-line industrial process control to follow up only a single element (that with the lowest LOD in such matrix) as a marker for the correct alloying in metals and mixing in pharmaceuticals.

Exploiting LIBS as a spectrochemical analytical technique in diagnosis of some types of human malignancies.

In the present work we are presenting a detailed in vitro study of using laser-induced breakdown spectroscopy (LIBS) as a quick and simple method for spectrochemical analysis to identify and characterize some types of human malignancies. This has been performed via detection of the abundance of certain elements namely calcium and magnesium in malignant tissues with respect to the non-neoplastic ones. In order to improve the performance of the LIBS technique - in particular its sensitivity, reproducibility and limit of detection - the measurements have been performed under vacuum (10(-2) Torr) and the samples were frozen down to -196 degrees C in a specially designed vacuum chamber. Under such experimental arrangements a pronounced enhancement has been achieved in the signal to noise (S/N) ratio of different spectral lines. Significant discriminating results have been obtained in case of breast and colorectal cancers indicating the possibility of adopting LIBS in the early detection of the malignancy as well as the identification of the severity and the grade of the disease. The present work demonstrated that future in vivo measurements are also feasible and reliable using especial endoscopic systems for delivery of laser beam and collection of the emitted plasma light.

Time-resolved LIBS experiment for quantitative determination of pollutant concentrations in air

We propose a new time-resolved laser-induced breakdown spectroscopy (TRELIBS) system for quantitative determination of small amounts of pollutants in gas. Some experimental results showing the high resolution of the method are reported, and possible improvements of the system are discussed.

Influence of biological degradation and environmental effects on the interpretation of archeological bone samples with laser-induced breakdown spectroscopy

Laser Induced Breakdown Spectroscopy (LIBS) has emerged in the past decade as a very promising technique for the analysis and characterization of a broad variety of objects of cultural heritage especially bio-archeological samples such as calcified tissues namely teeth and bones. The most important advantages of LIBS from the archeological point of view are its quasi nondestructive nature and its potential for performing in situ measurements. In the present work human calcified tissue samples of recent and archeological bones have been studied via the LIBS technique. The old samples were from three different ancient Egyptian dynasties representing the middle kingdom (1980–1630 BC), the 2nd intermediate period (1630–1539/23 BC) and the pre-Roman period (664 BC). Elements normally used to study dietary habits such as strontium, barium, aluminium and lead were analyzed in the obtained LIBS spectra and the interferences of postmortem or diagenic effects due to the burial place were investigated viaLIBS analysis of soil samples taken from the same locations where the archeological bones have been buried. The obtained results have demonstrated evidently that conclusions about dietary habits must take into account postmortem effects such as biological degradation and environmental leaching (especially from the surrounding soil). Study of CN and C2 molecular bands in the obtained LIBS spectra of the bones revealed that these bands have strong intensities in recent bones spectra contrary to the archaeological ones. This is attributed to the degradation of the tissues and has been confirmed by following up calcium to phosphorus ratios in different bone samples.

Diagnostics of high-temperature steel pipes in industrial environment by laser-induced breakdown spectroscopy technique: the LIBSGRAIN project

Abstract In this paper are presented the results of the feasibility study for the application of non-destructive spectroscopic methods to the diagnostics of steel pipes in industrial environment. The activities here described are part of the LIBSGRAIN project, funded by the European Commission; the main aim of the project is correlating the probability of failure of industrial plants components with the results of space-resolved elemental analysis carried out with laser-induced breakdown spectroscopy (LIBS) technique. Several simulations have been made in order to check the detectability of dangerous deterioration of steel pipes and to optimize some experimental parameters as the laser focal spot size and the traverse scanning step of the laser head. A design of a laser head which can operate in a real plant and can overcome the problems related to high temperature and vibration is proposed. The feasibility of remote controlled measurements at high temperature has been demonstrated in laboratory tests. The accuracy of LIBS measurements on steel target has been tested on NIST certified steel samples.

Analysis of explosive residues in human fingerprints using optical catapulting–laser-induced breakdown spectroscopy

Optical catapulting in combination with laser induced breakdown spectroscopy (OC-LIBS) is a new developing technique that has been effectively tested for the analysis of solid aerosols. In the present work OC-LIBS has been used to analyze explosive residues in human fingerprints left on glass surfaces in the form of solid aerosols. Experimental conditions such as the temporal acquisition delay, the distance from the surface and the interpulse delay time between lasers are studied. Explosives residues (TNT, DNT and MNT) and confusant materials (oil and Bermuda grass smut spores) were identified by OC-LIBS. Chemical images generated by OC-LIBS provided visual information on the spatial distribution of the explosive residue in the fingerprints. Advantages of OC-LIBS over conventional LIBS include the absence of contamination of the specimen analyzed and the freedom from spectral contribution of the substrate where the sample was placed.

Photodynamic ability of silver nanoparticles in inducing cytotoxic effects in breast and lung cancer cell lines

License. The full terms of the License are available at http://creativecommons.org/licenses/by-nc/3.0/. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. Permissions beyond the scope of the License are administered by Dove Medical Press Limited. Information on how to request permission may be found at: http://www.dovepress.com/permissions.php International Journal of Nanomedicine 2014:9 3771–3780 International Journal of Nanomedicine Dovepress

Assessment of DNA Damage after Photodynamic Therapy Using a Metallophthalocyanine Photosensitizer

Photodynamic therapy (PDT) is a chemotherapeutic approach that utilizes a bifunctional reagent, a photosensitizer (PS) that localizes to the target tissue relative to the surrounding tissue and is toxic when exposed to laser light. PDT rapidly induces cell death, inflammatory and immune reactions, and damage of the microvasculature. DNA damage results from a variety of factors including UV-light, X-rays, ionizing radiation, toxins, chemicals, or reactive oxygen species. The aim of this study was to determine the effect of PDT as well as the influence of presensitization leading to the adaptive response (AR) on the integrity of DNA. Lung (A549), breast (MCF-7), and esophageal (SNO) cancer cells and Zn sulfophthalocyanine as PS with irradiation conditions of 10 J/cm2 at 636 nm were used. Subcellular localization of PS, cell morphology, and viability after PDT and DNA damage were determined. A significant decrease in viability and marked DNA damage was observed in all 3 cancer cell types in response to PDT while the adaptive response was demonstrated to significantly decrease the effectiveness of the PDT.

Laser spectrochemical characterization of semen

The overall objective of this paper is to use a fast, more sensitive and less costly spectrochemical analysis laser techniques for estimation of seasonal variation of elements present in seminal plasma as well as for semen sperm count. For these two tasks we used Laser Induced-Breakdown Spectroscopy (LIBS) as an elemental analysis technique and Laser Induced Fluorescence (LIF) as a molecular analysis technique for sperm count estimation. The samples investigated via both techniques were buffalo semen from the artificial insemination center at the faculty of agriculture. The obtained LIBS data helped to assess indirectly the semen quality, sperm motility and spermatozoa count, relevant to the studied elements in different seasons. In addition it has been demonstrated that LIF can be adopted directly in centers of artificial insemination as a simple and fast method for the essential step of semen counting instead of the lengthy and inaccurate conventional techniques.