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Öğe Silica gel-immobilized 5-aminoisophthalohydrazide: A novel sorbent for solid phase extraction of Cu, Zn and Pb from natural water samples(Wiley Online Library, 2020-03-11) Aydın, Funda; Çakmak, Reşit; Levent, Abdulkadir; Soylak, MustafaA novel silica sorbent, silica gel‐immobilized 5‐aminoisophthalohydrazide (SiO2‐APH), was prepared by the condensation of 3‐chloropropyl‐functionalized silica gel with 5‐aminoisophthalohydrazide (APH) derived from dimethyl 5‐aminoisophthalate as a starting material and used for separation and preconcentration of Cu, Zn, and Pb metals in water samples using Flame Atomic Absorption Spectrometry (FAAS). The characterization of the new sorbent was carried out by Elemental Analysis, Thermogravimetric Analysis (TGA) and Fourier Transform Infrared Spectroscopy (FTIR). Important analytical parameters including as pH, amount of sorbent, type and amount of eluting solvent, sample volume, vortex and ultrasonic bath time, matrix ions that effect the developed SiO2‐APH‐solid phase extraction (SPE) method were investigated and optimum parameters were detected. Recoveries of examined metals were obtained as 98% for Cu and Pb and 101% for Zn. The relative standard deviation (RSD, n = 8) of Cu, Zn and Pb metals were 3.2, 2.8 and 1.6%, respectively. Limit of detections (LODs) (n = 10) were found as 2.7 μg L−1 for Cu, 7.4 μg L−1 for Zn and 3.5 μg L−1 for Pb μg L−1. The accuracy of the new method was assessed by analyzing of TMDA‐51.4 and TMDA‐70.2 certified reference materials. The results obtained for metals were in a good agreement with certified values. Addition/recovery test was applied to the real well, river, dam and stream water samples to check the accuracy of the method. The results showed that the developed SiO2‐APH‐SPE method can be effectively used as an alternative method for determination of Cu, Zn, and Pb metals in water samples.Öğe Voltammetric behavior of testosterone on bismuth film electrode: Highly sensitive determination in pharmaceuticals and human urine by square‐wave adsorptive stripping voltammetry(Wiley Online Library, 2015-03-20) Levent, Abdulkadir; Altun, Ahmet; Taş, Süleyman; Yardım, Yavuz; Şentürk, ZühreIn this paper, an electrochemical application of bismuth‐film electrode (BiFE) fabricated via ex‐situ electrodeposition onto a glassy carbon electrode for testosterone determination was investigated in aqueous and aqueous/surfactant solutions. In cyclic voltammetry, the compound showed one irreversible and adsorption‐controlled reduction peak. The BiFE revealed good linear response in the examined concentration range of 1 to 45 nmol L−1 testosterone in BrittonRobinson buffer, pH 5.0 containing 3 mmol L−1 cetyltrimethylammonium bromide. The limit of detection was 0.3 nmol L−1 (0.09 ng mL−1). Finally, the BiFE was satisfactorily applied for quantitation of testosterone in both pharmaceutical (oil‐based ampoule) and biological (human urine) samples.Öğe An experimental investigation on bushing geometrical properties and density in thermal frictional drilling(Multidisciplinary Digital Publishing Institute (MDPI), 2018-12-18) Demir, Zülküf; Özek, Cebeli; Bal, MuhammedIn thermal friction drilling (TFD) operations, the geometrical dimensions of bushing shape, height and wall thickness are the most vital consequences, since these increase the connecting length and strength. In this paper, AA7075-T651 aluminum alloys with 2, 4, 6, 8, and 10 mm thicknesses were drilled with the TFD process in order to investigate density, volume ratio, and height and wall thickness of the bushings. The experiments were conducted at constant spindle speed and feed rate conditions by using High Speed Steel (HSS) conical tools of 5, 10, 15, and 20 mm in diameter. It was experimentally found that the bushing height and the wall thickness had a tendency to increase linearly with the increase in both material thickness and tool diameter. The effect of tool diameter was found to have more influence on the measurable values than the thickness of the drilled material. The density of the bushing changed trivially. Approximately 70-75 percent of the evacuated material formed the bushing shape in TFD operations.Öğe Determination of Cu contamination in some spring and mineral waters around van by AAS after enrichment of activated carbon(Medwell, 2011) Dağ, Beşir; Kılıçel, FevziSome trace metal contamination in water is a major component in the determination of water quality. In order to supply qualify water for health of human being, terrestiral and aquatic animals is very important. Apparently, tap water and spring water qualities in many countries are effected by industrilization and over population. The main aim of this study was to detect copper metal concentration in some spring and mineral water around Van by means of Atomic Absorption Spectrometer after enrichment of activated carbon. Spring and mineral water samples were collected some different parts of city. These mineral and spring water samples were determined by a simple preconcentration method which is called activated carbon enrichment. The metal analysis was done to detect copper element. It was compared the results with standarts for drinking water quality of World Health Organization (WHO) and Europian Union drinking water standarts. As a result, copper level in the spring and mineral water around Van were generally suitable for the both criterias of World Health Organization (WHO) and Europian Union drinking water.Öğe Electrooxidation of thiourea and its square-wave voltammetric determination using pencil graphite electrode(Walter de Gruyter, 2011-04-01) Levent, Abdulkadir; Keskin, Ertuğrul; Yardım, Yavuz; Şentürk, ZühreThe electrochemical properties of thiourea (TU) were investigated in pH range 2.0-12.0 by cyclic and square-wave voltammetry. The compound was irreversibly oxidized at a pencil graphite electrode in one or two oxidation steps which are pH-dependent. Based on the voltammetric peak for the second oxidation process of TU in phosphate buffer at pH 12.0, a square-wave voltammetric method was proposed for the determination of the compound in the range 6.3-30μm, with a detection limit of 1.29μm. The applicability to direct assays of wastewaters was also tested.Öğe An experimental investigation of the effects of point angle on the high-speed steel drills performance in drilling(SAGE, 2018-11) Demir, ZülküfThe differences in the cutting speed are a serious problem along the cutting edge of the drill, in drilling operations. This problem can partly be solved reducing the length of the cutting edge via changing the drill point angle. In addition, in this study, the effect of point angle, feed rate, and cutting speed on drilling is investigated. For identifying the optimum cutting parameters, AISI 1050 steel alloy was selected as the experimental specimen, these specimen were pre-drilled 5 mm in diameter due to eliminating the effect of the chisel edge. In the experiments, the holes were drilled only at a depth of 10 mm in order not to give any harm to the dynamometer while measuring thrust force. For this aim, in drilling process, drills with point angle of 100°, 118°, 136°, 154°, and 172° were selected. In conclusion, the thrust force, the tool wear, and the surface roughness linearly decreased with increasing point angles due to less removal chip area, in per revolve of the tool. However, the thrust force, the tool wear, and the surface roughness were adversely affected at higher feed rates and lower cutting speeds. The hole dimensional accuracy decreased at lower feed rates and cutting speeds but at higher point angles and concurrently at higher feed rates but lower point angles and cutting speeds. However, the hole dimensional accuracy showed more decisiveness at 118° than other point angles, while the highest dimensional accuracy values recorded at 136° point angle, at higher cutting speeds.
