Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 29Citation - Scopus: 29Investigating Silicon Wafer Based Substrates for Dried-Droplet Analysis by Laser-Induced Breakdown Spectroscopy(Elsevier Ltd., 2019) Aras, Nadir; Yalçın, ŞerifeThis work communicates a critical assessment on the analytical capability of the three silicon wafer-based substrates; crystalline silicon (c-Si), oxide-coated silicon (SiO2-Si), and nitride-coated silicon (Si3N4-Si), for dried-droplet analysis by laser-induced breakdown spectroscopy. The methodology consists of loading, drying and analyzing steps. First, nanoliter volume of droplets are manually loaded onto the substrate and dried at room temperature. Then, the dry residue is subjected to high peak power (1.15 GW/cm(2)) laser pulses focused outside the minimum focal point condition and luminescent plasma is spectroscopically analyzed. Results revealed that nitride-coated substrate exhibits strong enhancements in signal intensity for most emission lines of the analyte species investigated: Cd, Cr, Cu, Mn, and Pb. Surface reflectivity and surface morphology were comparatively investigated to explore enhanced analytical performance of nitride-coated substrates. Experimental conditions were optimized and growth curves for all the elements are found linear with minimum regression constant of 0.96. LOD's of 62 pg Cd, 1.5 pg Cr, 0.5 pg Cu, 2 pg Mn and 11 pg Pb, in absolute amounts, were obtained. The accuracy and precision of the methodology were tested on certified reference water sample (CRM-TMDW), and ICP-multi-element standard sample (ICP-MES). The surface enhancement effect observed on Si3N4 coated substrates has improved the analytical capability of laser-induced breakdown spectroscopy for liquid analysis.Article Citation - WoS: 62Citation - Scopus: 64Ultrasonic Nebulization-Sample Introduction System for Quantitative Analysis of Liquid Samples by Laser-Induced Breakdown Spectroscopy(Elsevier Ltd., 2012) Aras, Nadir; Ünal Yeşiller, Semira; Ateş Arıca, Dilek; Yalçın, ŞerifeIn 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: 21Citation - Scopus: 23Determination of Caco 3 and Sio 2 Content in the Binders of Historic Lime Mortars(Springer Verlag, 2012) Uğurlu Sağın, Elif; Böke, Hasan; Aras, Nadir; Yalçın, ŞerifeThe binders of historic mortars composed of small grain sized silica (SiO 2) and carbonated lime (CaCO 3) are considered as the main part that give hydraulic character and high strength to the mortar. In this study, FTIR, SEM-EDS, LIBS and XRD spectroscopy were used to find out the weight ratios of CaCO 3 to SiO 2 in the binders of historic lime mortars. For this purpose, a series of pure calcium carbonate and silica mixture were prepared in ten combinations in varying ratios from 0.5 to 5. Calibration curve was prepared for each analysis by plotting the peak area or intensity ratios of CaCO 3 to SiO 2 versus the weight ratios of CaCO 3 to SiO 2. A good linear correlation coefficient was obtained for each analysis respectively. The analyses were then tested on the binder of the Roman mortar samples. The results indicated that FTIR, SEM-EDS and LIBS spectroscopy are convenient tools to determine the weight ratios of CaCO 3 to SiO 2 in the binders of mortars. But XRD spectroscopy is not convenient for quantitative analysis of binders due to the presence of varied amounts of amorphous or poor crystalline silica in their compositions.Article Citation - WoS: 9Citation - Scopus: 9Rapid Identification of Phosphorus Containing Proteins in Electrophoresis Gel Spots by Laser-Induced Breakdown Spectroscopy, Libs(Royal Society of Chemistry, 2014) Aras, Nadir; Yalçın, ŞerifeA novel method for the rapid in-gel identification of phosphorus containing proteins, specifically casein and ovalbumin, prior to mass spectrometric analysis for the elucidation of phosphorylation sites was developed. After polyacrylamide gel-electrophoretic separation, staining and drying, protein bands were subjected to focused laser pulses at the center or the vicinity of the protein band. Phosphorus containing proteins were recognized from their prominent phosphorus lines in the luminous plasma formed by energetic laser pulses. The LIBS emission intensity of phosphorus lines at 253.5 nm and 255.3 nm has been optimized with respect to laser energy and detector timing parameters by using pure casein in the pellet form. The method was applied to casein, ovalbumin, two commercially available standard protein mixtures and proteins extracted from the canola plant. It was shown that LIBS was capable of identifying phosphorus containing proteins directly in the gel matrix in nanogram amounts. Mass spectrometric analysis of the ovalbumin spot after the in-gel digestion procedure has proved the accuracy of the technique. With the speed and spatial resolution that LIBS offers, this technique shows promise in the micro-local spotting of phosphorus containing proteins in the polyacrylamide gel matrix prior to MS analysis for the determination of the phosphorylation sites. © 2014 The Royal Society of Chemistry.