Sürdürülebilir Yeşil Kampüs Koleksiyonu / Sustainable Green Campus Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7755

Browse

Filters

2012 - 20133

Settings

Institution Author: search.filters.institutionAuthor.Ünal Yeşiller, Semira

Search Results

Now showing 1 - 3 of 3
  • Article
    Citation - WoS: 62
    Citation - Scopus: 64
    Ultrasonic Nebulization-Sample Introduction System for Quantitative Analysis of Liquid Samples by Laser-Induced Breakdown Spectroscopy
    (Elsevier Ltd., 2012) Aras, Nadir; Ünal Yeşiller, Semira; Yalçın, Şerife; Yalçın, Şerife; Aras, Nadir; 03.07. Department of Environmental Engineering; 04.01. Department of Chemistry; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of Technology
    In this study, design and optimization studies of a sample introduction system based on ultrasonic nebulization of metal salts in aqueous environment for laser-induced breakdown spectroscopic detection were presented. The system consisted of an ultrasonic nebulizer connected to a tandem heater-condenser- membrane dryer unit that produces sub-micron size aerosols. Results indicate improvements in detection limits for some elements with the use of membrane dryer. Optimization studies were performed by systematical investigation of LIBS emission signal with respect to laser energy, carrier gas flow rate and detector timing parameters. Under optimized conditions, calibration graphs for Na, K, Mg, Ca, Cu, Al, Cr, Cd, Pb and Zn were constructed and detection limits were calculated. The applicability of the ultrasonic nebulization-LIBS system was tested on real water samples. This system establishes LIBS as an effective analytical tool for both qualitative and quantitative determination of metal aerosols in aqueous environments. This technique is sufficiently rapid to provide real-time monitoring of toxic metals.
  • Article
    Citation - WoS: 23
    Citation - Scopus: 22
    Optimization of Chemical and Instrumental Parameters in Hydride Generation Laser-Induced Breakdown Spectrometry for the Determination of Arsenic, Antimony, Lead and Germanium in Aqueous Samples
    (Elsevier Ltd., 2013) Ünal Yeşiller, Semira; Yalçın, Şerife; Yalçın, Şerife; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    A laser induced breakdown spectrometry hyphenated with on-line continuous flow hydride generation sample introduction system, HG-LIBS, has been used for the determination of arsenic, antimony, lead and germanium in aqueous environments. Optimum chemical and instrumental parameters governing chemical hydride generation, laser plasma formation and detection were investigated for each element under argon and nitrogen atmosphere. Arsenic, antimony and germanium have presented strong enhancement in signal strength under argon atmosphere while lead has shown no sensitivity to ambient gas type. Detection limits of 1.1mgL-1, 1.0mgL-1, 1.3mgL-1 and 0.2mgL-1 were obtained for As, Sb, Pb and Ge, respectively. Up to 77 times enhancement in detection limit of Pb were obtained, compared to the result obtained from the direct analysis of liquids by LIBS. Applicability of the technique to real water samples was tested through spiking experiments and recoveries higher than 80% were obtained. Results demonstrate that, HG-LIBS approach is suitable for quantitative analysis of toxic elements and sufficiently fast for real time continuous monitoring in aqueous environments.
  • Doctoral Thesis
    Design, Construction and Optimization Studies of a Hydride Generation Laser-Induced Breakdown Spectrometric System, (hg-Libes), for the Determination of Toxic Elements in Aqueous Samples
    (Izmir Institute of Technology, 2013) Ünal Yeşiller, Semira; Yalçın, Şerife; Yalçın, Şerife Hanım; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    In this thesis study, design, construction and optimization of a continuous flow hydride generation laser-induced breakdown spectroscopic system, HG-LIBS, for the determination toxic and environmentally important elements: arsenic, selenium, lead, antimony, tin, bismuth, germanium and tellurium, has been performed. The HG-LIBS system, which has been constructed from its commercially available components, consisted of four main parts: a laser source, a hydride generation unit, a sample/plasma cell and a detection unit. In order to maximize LIBS emission signal, some instrumental parameters such as laser energy and detector gating parameters were investigated. Some chemical parameters such as acid/reductant concentration and flow rate, carrier gas type and flow rate, presence of pre-reducing/oxidizing agent that effect hydride generation efficiency and transportation of hydrides were also studied. Under optimized conditions detection limits of 0.2 mg L-1, 1.1 mg L-1, 1.0 mg L-1, 1.3 mg L-1 and 0.2 mg L-1 were obtained for Sn, As, Sb, Pb and Ge, respectively. No analytical signal could be detected from Se and Te elements with the system developed. The applicability of the HG-LIBS system for the determination of As, Sb, Pb and Ge in aqueous environments has been tested on several real water samples including tap water, drinking water and reference river water standard. Temporal variation of electron temperature and electron density values for tin and germanium hydride plasma was determined under argon and nitrogen environment. Electron temperatures were calculated by making use of neutral atomic lines in Boltzmann equation. Plasma electron density was evaluated from the Stark-broadened line shapes of Hα line at 656.3 nm. In order to investigate the main cause of increase in germanium signal under argon environment, physical plasma parameters were evaluated in argon and nitrogen gas mixtures. With this thesis study, the applicability of the HG-LIBS system for on-line monitoring of environmental pollutants has been shown.