Yazar "Henden, E" seçeneğine göre listele
Listeleniyor 1 - 9 / 9
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Application of molecular emission cavity analysis to the determination of tin in various samples based on hydride generation(Elsevier Science Bv, 1996) Celik, A; Henden, EDetermination of the total amount of tin by molecular emission cavity analysis (MECA) after generation of stannane by means of reduction with sodium tetrahydroborate(III) and measuring the SnH emission within the flame-containing MECA cavity is described. The volatile hydrides of tin, germanium and arsenic were separated on a short gas chromatographic column. The calibration graph was linear over the range 5-250 ng Sn, and the detection limit (S/N=21) was 5 ng Sn, and the relative standard deviation for the determination of 50 ng Sn was 2.8% (n=8), The method was applied successfully to the determination of total tin in fish, canned soft drinks and sea sediment samples. Hydride generation recovery from soil sample solutions, however, was low.Öğe Comparison of Moss and Bark Samples As Biomonitors of Heavy-Metals In a Highly Industrialized Area In Izmir, Turkey(Elsevier Science Bv, 1995) Turkan, I; Henden, E; Celik, U; Kivilcim, SThe moss, Hypnum cupressiforme and bark of the pine, Pinus brutia have been used for passive monitoring of airborne heavy metal pollution by an iron-steel mill of an industrialised area of Izmir, Turkey. Six metals, lead (Pb), cadmium (Cd), zinc (Zn), chromium (Cr), manganese (Mn) and iron (Fe) have been monitored using atomic absorption spectrometry. Between 26.2.1992 and 13.8.1992 samples were taken on five occasions at a distance of 0.25, 1.0 and 2.5 km from the mill. The results show an accumulation of all six metals, with differences between the moss and bark samples and a decrease in concentration with distance from the mill. The arithmetic means of the measured heavy metal concentrations in the moss, Hypnum cupressiforme, were always much higher than those in the bark of the P. brutia, indicating that the moss H. cupressiforme is more suitable than the bark of P. brutia for use in monitoring heavy metal pollution. The results show that the study area, within 2.5 km from the iron-steel mill, is heavily polluted.Öğe Determination of selenoamino acids by gas chromatography-mass spectrometry(Elsevier Science Bv, 2004) Iscioglu, B; Henden, EThe application of the recently introduced ethylchloroformate derivatization method for the separation and determination of selenomethionine and selenocystein in selenium-enriched yeast and yeast-free tablets by means of a gas chromatography-mass spectrometry (GC-MS) system has been studied. The efficiency of three methods for the extraction of selenomethionine from the tablets were compared. Total selenium content of the same tablets were measured using inductively coupled plasma (ICP)-MS and it was found that in the selenized yeast tablets about 80% of the total selenium is present as selenomethionine. The results were in agreement with the values in the labels and with the literature. The accuracy of the total selenium analysis was controlled by the analysis of a reference material. (C) 2003 Elsevier B.V. All rights reserved.Öğe Fiber optic sodium and potassium sensing by using a newly synthesized squaraine dye in PVC matrix(Elsevier Science Bv, 2002) Ertekin, K; Tepe, M; Yenigul, B; Akkaya, EU; Henden, EIn recent years squarines received attention as fluorescent labels. Their very promising spectral properties such as long wavelength absorption and emission, high extinction coefficients and quantum yields could lead novel sensing technologies. In this work newly synthesized fluoroinophores named bis[4-N-(1-aza-4,7,10,13-tetraoxacyclopentadecyl)-3,5-dihydroxyphenyl]squaraine, azacrown-1 and 2 bis[4-N-(1-aza-4,7,10,13,16-pentaoxacyclooctadecyl)-3,5-dihydroxyphenyl]squaraine, azacrown-2 have been used for sodium and potassium sensing in plasticized PVC matrix. The squaraine derivatives exhibited fluorescence emission based optical responses to sodium and potassium with a detection limit of 1.10(-9) M. The sensor compositions exhibited wide response ranges between 10(-9) and 10(-5) M Na+ or K+, and, therefore, may be an alternative method to flame emission spectroscopy. The sensor is fully reversible within the dynamic range and the response time is 3 min under batch conditions. Cross sensitivity to pH is negligible in the pH range of 6.2-7.3. Throughout fiber optic based studies a relative signal change of 54-56% has been achieved. The azacrown dyes have the advantage that they can be excited with long wavelength light and, are, therefore, LED compatible. The cross sensitivity of azacrown-1 and -2 to Ba2+ Ca2+ and NH4+ were also tested in separate solutions. (C) 2002 Elsevier Science B.V. All rights reserved.Öğe Fluorescence emission studies of an azlactone derivative embedded in polymer films - An optical sensor for pH measurements(Elsevier Science Sa, 2000) Ertekin, K; Alp, S; Karapire, C; Yenigul, B; Henden, E; Icli, SAzlactone molecules can be protonated in acidic media, and the process of protonation is irreversible due to ring opening in solutions. A new fully reversible pH sensor has been developed 4-(p-N,N-dimethylamino phenyl methylene)-2-phenyl-5-oxazolone (DPO), an azlactone derivative, embedded in a plasticized PVC polymer film. The sensor membrane is completely transparent and exhibits pH induced color change which is capable of measuring of pH in the range 1-7 and has a pK(a) value of 3.4. In agreement with crystal phase studies, DPO displays enhanced fluorescence emission quantum yield, Q(f) = 0.52, and fluorescence emission lifetime, tau (f) = 1.35 ns, in immobilized PVC film matrix, compared to Q(f) congruent to 0.03 and tau (f) = 0.02-0.03 ns in solutions. Stokes shift decreased to 46 nm in plasticized PVC film, with respect to Stokes shift of 81 nm in acetonitrile solution. Singlet energy, E-s = 60.4 kcal mol(-1), of DPO in PVC film, which is 1.1-1.4 kcal mol(-1) lower with respect to solutions, is taken as evidence of lessened singlet-triplet crossings in excited state of DPO in immobilized phase, and result in enhanced fluorescence emissions. (C) 2000 Elsevier Science B.V All rights reserved.Öğe Inter-element interferences in the determination of arsenic and antimony by hydride generation atomic absorption spectrometry with a quartz tube atomizer(Elsevier Science Bv, 2004) Erdem, N; Henden, EThe interferences between arsenic and antimony on each other during the hydride generation atomic absorption spectrometry (HGAAS) determination of arsenic and antimony using a quartz tube atomizer (QTA) were examined. In order to eliminate or reduce such interferences by selective heat decomposition of arsine and stibine, a Pyrex adsorption U-tube trap containing glass wool was placed between the drying tube and the quartz tube atomizer. Although at 250degreesC stibine decomposes and is held almost completely by the trap, arsine is also decomposed to an extent of 24% and, therefore, thermal decomposition is not useful to eliminate antimony interference on arsenic determination. The effect of coating the glass wool in the U-tube with antimony on the arsenic suppression of the antimony signal was studied. The results showed that the antimony coating in the U-tube could not hold arsenic effectively and its interference on the antimony signal could not be eliminated by this means. In the second part of the study, oxygen was supplied to the quartz tube atomizer during atomization in order to study the effect of supplying oxygen on the antimony signal and on the interference of arsenic in the antimony determination. Sensitivity was increased in the presence of oxygen and interferences of arsenic on antimony determination was decreased by about 10% when oxygen was supplied. It was also observed that the extent of interferences depended mainly on the interferent concentration rather than the analyte concentration. (C) 2003 Elsevier Science B.V. All rights reserved.Öğe Interferences in the quartz tube atomizer during arsenic and antimony determination by hydride generation atomic absorption spectrometry(Pergamon-Elsevier Science Ltd, 2000) Ay, U; Henden, EInterferences of some metals in the determination of arsenic by hydride generation atomic absorption spectrometry utilizing a quartz tube atomizer were studied. The atomizers were coated under vacuum with Ni, Au, Pd and Cr. The arsenic signal was almost totally suppressed by all the metal coatings and thus the interferences from metal ions in the determination of arsenic were attributed both to the carry over of the reaction mixture, as well as interferences in the hydride formation step. Inter-element interferences by arsenic and antimony on each other in the atomizer of the same system were also studied. When arsine and stibine reach the atomizer at the same time they suppress each other's signals. The interference of arsenic on antimony was eliminated by simply separating arsine, which elutes first, from stibine using a simple gas chromatographic column (GC column). However, even when arsine and stibine are separated using the GC column, antimony is deposited in the quartz tube atomizer at the temperatures the quartz tube attains when heated in the air-acetylene flame, suppressing the arsenic signal in subsequent experiments. Therefore, directing of stibine outside of the atomizer, after elution of arsine from the GC column, was suggested for arsenic determination. (C) 2000 Elsevier Science B.V. All rights reserved.Öğe Investigation of soil pollution levels for lead, cadmium, zinc, chromium, nickel, manganese and iron around iron-steel industry near Izmir, Turkey(Trans Tech Publications Ltd, 1997) Henden, E; Turkan, I; Kivilcim, S; Celik, U; Incecik, S; Ekinci, E; Yardim, F; Bayram, ALevels of heavy metal pollution in soil around of an iron-steel mill of in industrial area in Aliaga City near Izmir,Turkey, were investigated. Six metals, Pb, Cd, Zn, Cr, Mn and Fe were determined using an atomic absorption spectrophotometer. Samples from the depth of 0-5 cm and 5-15 cm, were taken on five occasions between the dates 26.2.1992 and 13.08.1992 at distances of 0.5,1.0 and 2.5 km from the mill. The results show a remarkable differences in the contents of metals investigated according to the distance from the mill and sampling date and soil profile. The levels of the metals were found, in most of the samples, to be above the acceptable limits and/or the natural values. In most of the soil profiles, a clear decrease with depth, towards background values has been observed. The results show that the study area within 2.5 km from the iron-steel mill, is heavily polluted.Öğe A study of air pollution with heavy metals in Denizli City (Turkey) using olive (Olea europaea L.) as biological monitor(Trans Tech Publications Ltd, 1997) Turkan, I; Celik, U; Henden, E; Incecik, S; Ekinci, E; Yardim, F; Bayram, AIn this study, the level of heavy metal pollution by lead, cadmium, zinc and copper in Denizli City (Turkey) were investigated by use of olive (Olea europaea L.) as biological monitor. Seven sites near main roads were selected in the city of Denizli. Leaves of olive were sampled four times between the dates 10.25.1994 and 07.24.1995 at the distance of 0-4 m and 125-175 m, from the main roads. Present results showed that the concentrations of leads cadmium and zinc on the plants exceeded the and normal levels, and site 4 with heaviest traffic density was the most contaminated with heavy metals. The levels of heavy metals in the leaves of olive decreased with an increase in distance from the road.
