Yazar "Chormey, Dotse Selali" seçeneğine göre listele

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    A novel liquid-liquid extraction for the determination of naphthalene by GC-MS with deuterated anthracene as internal standard
    (Springer, 2017) Erarpat, Sezin; Ozzeybek, Gozde; Chormey, Dotse Selali; Erulas, Fatih; Turak, Fatma; Bakirdere, Sezgin
    Polycyclic aromatic hydrocarbons are known for their carcinogenic and mutagenic effects on human health. This therefore calls for the regulation of their concentrations in air, water, and soil. Naphthalene as the simplest in structure of the polycyclic aromatic hydrocarbons is mainly used as a starter material for other chemicals but also has impacts on human health. A method is therefore proposed for the determination of naphthalene in water samples by gas chromatography mass spectrometry after liquid-liquid extraction. The extraction method was optimized to improve the extraction output, thereby lowering the limit of detection. The limits of detection and quantification obtained for naphthalene were 4.4 and 14.6 ng mL(-1), respectively. Deuterated anthracene was used as internal standard to enhance the precision of the method, for which a relative standard deviation of 4.3% was obtained. The percent recovery of naphthalene obtained from tap water was ranged between 93.8 and 102.2.
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    Accurate and simple determination of oxcarbazepine in human plasma and urine samples using switchable-hydrophilicity solvent in GC-MS
    (Wiley, 2020) Erarpat, Sezin; Bodur, Suleyman; Ayyildiz, Merve Firat; Gunkara, Omer Tahir; Erulas, Fatih; Chormey, Dotse Selali; Turak, Fatma
    This work presents a sensitive and rapid analytical method for the determination of oxcarbazepine in human plasma and urine samples. A vortex-assisted switchable hydrophilicity solvent-based liquid phase microextraction (VA-SHS-LPME) was used to preconcentrate oxcarbazepine from the samples before the determination by gas chromatography mass spectrometry. The switchable hydrophilicity solvent was synthesized by protonatingN,N-dimethylbenzylamine with carbon dioxide to make it totally miscible with an equivalent volume of water. Parameters of the VA-SHS-LPME method including volume of switchable hydrophilicity solvent, concentration/volume of sodium hydroxide and vortex period were systematically optimized. Under the optimum conditions, good linearity ranging from 27.03 to 353.47 mu g/kg was obtained for the analyte. Limit of detection and quantitation values were found to be 6.2 and 21 mu g/kg (mass base), respectively. The relative standard deviation was calculated as 6.9% for six replicate measurements of the lowest concentration of the calibration plot. Satisfactory recovery results were calculated in the range of 97-100% for human plasma and urine samples spiked at five different concentrations.
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    Accurate determination of pesticides, hormones and endocrine disruptor compounds in complex environmental samples using matrix dilution and matrix matching with dispersive liquid-liquid microextraction
    (Walter De Gruyter Gmbh, 2018) Chormey, Dotse Selali; Firat, Merve; Buyukpinar, Cagdas; Erulas, Fatih; Komesli, Okan Tarik; Turak, Fatma; Bakirdere, Sezgin
    Quantitative determination of contaminants in environmental samples is usually hampered by low analyte recovery which results from the complex nature of the sample matrix. This study presents the application of a developed dispersive liquid-liquid microextraction method for the determination of 12 analytes in environmental samples including sea water, fresh water (lake, well and tap water), brackish water and soil samples. Matrix matched standards were used to compensate for the low analyte recovery recorded by the conventional calibration method. The effect of matrix dilution on analyte recovery was also tested. All matrix matched and matrix diluted spiked recoveries were done concurrently with calibration standards prepared in deionized water. Percent recoveries recorded for the analytes according to deionized water calibration standards ranged between 66 and 137 %. Matrix matching and matrix dilution yielded close to 100 % recovery results, but the later lowered the detection limit according to the dilution factor.
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    Arsenic speciation in water and biota samples at trace levels by ion chromatography inductively coupled plasma-mass spectrometry
    (Taylor & Francis Ltd, 2017) Firat, Merve; Bakirdere, Sezgin; Sel, Sabriye; Chormey, Dotse Selali; Elkiran, Omer; Erulas, Fatih; Turak, Fatma
    A sensitive, reliable, simple and rapid analytical method was developed for the determination of arsenite [As(III)], arsenate [As(V)] and arsenobetaine (AsB) species using ion chromatography combined with inductively coupled plasma-mass spectrometry (IC-ICP-MS). Inorganic and organic arsenic species were separated with an anion exchange column (Dionex AS9) and a 50mM sodium bicarbonate mobile phase (pH 10) at a flow rate of 1.0mL min(-1.) %RSD values were found to be lower than 5.1% for all arsenic species. The limits of detection (LOD) obtained for As(III), As(V) and AsB were 16.5 ng L-1, 14.1 ng L-1 and 6.2 ng L-1, respectively. The developed analytical method was tested using AsB certified reference material (NMIJ CRM 7901-a), and spring water certified reference material (UME CRM 1201) for accuracy check. This method was applied for the quantitative determination of arsenic species in different water samples and chicken samples as a solid matrix.
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    Combination of stearic acid coated magnetic nanoparticle based sonication assisted dispersive solid phase extraction and slotted quartz tube-flame atomic absorption spectrophotometry for the accurate and sensitive determination of lead in red pepper samples and assessment of green profile
    (Elsevier Sci Ltd, 2020) Zaman, Buse Tugba; Erulas, Ahmet Fatih; Chormey, Dotse Selali; Bakirdere, Sezgin
    This study describes the determination of lead at trace levels by slotted quartz tube flame atomic absorption spectrophotometry (SQT-FAAS) after preconcentration by the help of stearic acid coated magnetic nanoparticle (SAC-MNPs) based sonication assisted dispersive solid phase extraction (SA-DSPE). SAC-MNPs were used due to their easy separation advantages by the application of external magnetic field. All extraction parameters were optimized by response surface methodology based experimental design. The experimented data was evaluated by the analysis of variance. Under the optimum conditions, about 31 folds enhancement in detection power was obtained over the conventional FAAS. The recovery results obtained for samples spiked at 60 and 120 ng mL(-1) were 106.6 and 102.6%, respectively, validating the method as accurate and applicable to the red pepper matrix. The percent relative standard deviations of the results were under 5.0% even at low concentrations that established high precision for replicate extractions and instrumental readings.
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    Determination of levetiracetam by GC-MS and effects of storage conditions and gastric digestive systems on drug samples
    (Newlands Press Ltd, 2021) Erulas, Fatih Ahmet; Chormey, Dotse Selali; Oz, Ersoy; Bakirdere, Sezgin
    Background: Epilepsy is a neurologic condition that is occurs globally and is associated with various degrees of seizures. Levetiracetam is an approved drug that is commonly used to treat seizures in juvenile epileptic patients. Accurate quantification of the drug's active compound and determining its stability in the stomach after oral administration are important tasks that must be performed. Results & methodology: Levetiracetam was extracted from drug samples and quantified by gas chromatography mass spectrometry using calibration standards. Stability of levetiracetam was studied under various storage conditions and in simulated gastric conditions. The calibration plot determined for levetiracetam showed good linearity with a coefficient of determination value of 0.9991. The limits of detection and quantification were found to be 0.004 and 0.014 mu g center dot ml(-1), respectively. The structural integrity of levetiracetam did not change within a 4-h period under the simulated gastric conditions, and no significant degradation was observed for the different storage temperatures tested. Discussion & conclusion: An accurate and sensitive quantitative method was developed for the determination of levetiracetam in drug samples. The stability of the drug active compound was monitored under various storage and gastric conditions. The levetiracetam content determined in the drug samples were within +/- 10% of the value stated on the drug labels.
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    Oleic and stearic acid-coated magnetite nanoparticles for sonication-assisted binary micro-solid phase extraction of endocrine disrupting compounds, and their quantification by GC-MS
    (Springer Wien, 2019) Chormey, Dotse Selali; Akkaya, Erhan; Erulas, Fatih Ahmet; Bakirdere, Sezgin
    Nanosized magnetic nanoparticles (MNPs) were utilized for the preconcentration of 12 analytes including pesticides, alkylphenols, hormones and bisphenol A prior to their determination by GC-MS. The extraction efficiency of the MNPs was enhanced by coating them with oleic acid and stearic acid. A binary system consisting of the two kinds of coated MNPs was optimized using a multivariate experimental design which evaluated main experimental variables and their interactions. Under optimized conditions, the following figures of merit are found: (a) Enrichment factors ranging from 64 to 345; (b) detection limits between 0.13 and 2.7 mu g L-1; and (c) recoveries from spiked underground well water and municipal wastewater between 90 and 109%. The closeness of the results to 100% validated the method and underpinned its trueness for quantitative determinations.
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    Simultaneous Determination of Harmful Aromatic Amine Products of Azo Dyes by Gas Chromatography-Mass Spectrometry
    (Pleiades Publishing Inc, 2020) Chormey, Dotse Selali; Zaman, Buse Tugba; Maltepe, Esra; Buyukpinar, Cagdas; Bulgurcuoglu, Ayse Evrim; Turak, Fatma; Erulas, Fatih Ahmet
    Azo dyes constitute about 66% of all colorants and they are widely used in industries such as textiles, plastics, ceramics, cosmetics and food. However, due to the reductive cleavage of some azo dyes into carcinogenic aromatic amines, many countries have set concentration limits or have banned the use of these azo dyes. Selected aromatic amines that pose health risk to consumers were simultaneously determined by gas chromatography mass spectrometry. A good linearity in calibration plot was obtained for the analytes and the low relative standard deviations indicated high instrumental precision. A recovery test was performed to validate the extraction method and the results obtained were between 92-114%. The method was applied to the analysis of real samples and the concentrations of aromatic amines detected were below the 30 mg/kg limit set by regulatory authorities.