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    Determination of benzene, toluene, ethylbenzene, p-, m-, o-xylene, and n-butyl acetate in urine by a validated gas chromatography method: Application to an occupational monitoring study
    (Univ Sao Paulo, Conjunto Quimicas, 2025) Dural, Emrah; Kaya, Betul Isiner; Mergen, Gorkem; Boran, Erhan; Soylemezoglu, Tulin
    This study was aimed to determine occupational and non-occupational exposure to benzene, toluene p-m-o-xylene (BTEXs) and butyl-acetate (nBA). The aim of this work was to develop a simple, sensitive, and reliable chromatographic method using urine, a non-invasive human sample. The method was applied to samples collected from furniture spray workers (n=53) who are at risk of exposure to BTEXs and nBA and office workers (n=51) who have no known exposure risk. Method validation tests, include the sensitivity (LOD <= 0.018 ng/mL), precision (RSD <= 4.1), accuracy (RE% (-3.9)-4.7), recovery (96.1-103.8%) and linearity (r(2)>= 0.999). Urinary benzene (1.77 vs 1.23 ng/mL, exposed-control, respectively), toluene (51.22 vs 0.77 ng/mt), ethylbenzene (9.25 vs 6.69 ng/mt), para-xylene (1.73 vs 0.62 ng/mt), meta-xylene (2.58 vs 1.20 ng/mt), ortho-xylene (1.61 vs 0.88 ng/ mL), and butyl acetate (33.14 vs 1.63 ng/mL) concentrations were determined in the exposed and control group samples. Significant correlations were found between benzene (p=0.286*), ethylbenzene (p=0.552***) and o-xylene (p=0.292*) levels and smoking status in samples belonging to the control group. The occupationally-exposure-risk group samples have significantly higher BTEXs and nBA concentrations than the control (p<0.001). It was determined that smoking was a significantly effective factor in exposure to benzene, ethylbenzene and o-xylene in the control group.
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    Development and Validation of HPLC-UV Method for the Determination of Diclofenac in Human Plasma with Application to a Pharmacokinetic Study
    (TURKISH PHARMACISTS ASSOC, 2016) Arisoy, Gulsum Gul; Dural, Emrah; Mergen, Gorkem; Arisoy, Mustafa; Guvendik, Gulin; Soylemezoglu, Tulin
    A simple, rapid and reliable high performance liquid chromatography method (HPLC) with ultraviolet detection (UV) was developed and validated according to ICH guidelines, for quantitative analysis and therapeutic drug monitoring of diclofenac sodium (DS) in human plasma. Plasma samples (0.7 mL) were acid hydrolysis by 100 mu L, 1 M hydrochloric acid. Analytes were concentrated from plasma by liquid-liquid extraction with 2 mL ethyl acetate by repeated twice, which allows to obtain good extraction yields (98.75%-99.32%). The separation was achieved by employing C18 analytical column (3.5 mu m particle size, 150 mmx3.9 mm I.D.) under isocratic conditions using acetonitrile and NaH2PO4 mixture (42.5: 57.5, v/v) as mobile phase (pH: 3.16) flow rate of 1.5 mL/min. Naproxen (3 mu g/mL) was used as an internal standard (IS). The DS and IS were detected at 281 nm and eluted at 2.6 and 6.2 min, respectively. Total run time was 7 min. Method showed linearity with very good determination coefficients (r(2)=0.999), over the concentration range of 50 - 1600 ng/mL. Limits of detection (LOD) and quantification (LOQ) were 8.95 ng/mL and 27.12 ng/mL, respectively. Intra-day precision and accuracy were between 0.93-5.27; 1.74-9.81, respectively. Inter-day precision and accuracy were between 2.71-6.64; 2.03-9.16, respectively. This method was successfully applied for determination of DS plasma concentrations during a pharmacokinetic study in healthy volunteers (n=12) after an oral administration of Voltaren (R) 75 mg/tablet and remarkable variations in DS levels were observed. In our study, on the contrary to equivalent doses of DS, the observed significant differences in plasma levels of DS, on 2nd, 4th and 6th hours, can be explained by pharmacokinetic differences, that arise from mainly polymorphisms of CYP2C9 and CYP3A4, which are major enzymes responsible for DS metabolism.
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    INVESTIGATION OF THE RELATIONSHIP BETWEEN NICOTINE AND COTININE CONCENTRATIONS IN HUMAN BIOLOGICAL SAMPLES BY A GC-MS METHOD
    (Editura Acad Romane, 2023) Dural, Emrah; Kozluca, Hatice Taslak; Kaya, Betul Isiner; Mergen, Gorkem; Soylemezoglu, Tulin
    In this study, a gas chromatography-mass spectrometry method was developed for the determination of nicotine and cotinine wherein human plasma, urine, and saliva. In addition, it was aimed to determine statistically the correlation between nicotine and cotinine levels in urine and saliva samples and nicotine and cotinine levels in blood samples. The limit of quantification was <= 0.83 ng/mL and precision were <= 4.91 and accuracy (RE%) was between (-4.93) and 4.90. Recovery was detected between 95.4% and 104.7%. The method was employed to determining the nicotine and cotinine concentrations in plasma, saliva, and urine total of 91 samples belong to nonsmokers (n = 37) and active smokers (n = 54) who were healthy (n = 65) and COPD patients (n = 27) and the statistical relationship within the nicotine and cotinine values of the samples were investigated. It was found a correlation (r = 0.752, p <= 0.01) between plasma and saliva cotinine levels and estimation equation calculated as y = 1.56x + 43.24. Also, the correlation between plasma and urine cotinine levels was found (r = 0.787, p <= 0.01) by the equation that y = 0.31x + 34.59. The results show that by accurately determining the amount of cotinine in both saliva and urine, the exposure risks of both active smokers and those exposed to cigarette smoke with the ETS can be estimated.