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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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    Determination of Urinary Total Hydroxyproline by HPLC with UV and EC Detectors
    (CHEM SOC PAKISTAN, 2018) Kaya, Betul Isiner; Dural, Emrah; Kenduzler, Erdal; Soylemezoglu, Tulin
    Hydroxyproline is found in high concentrations in connective tissue proteins. It is remarkably useful to detect it because variation in urine levels of hydroxyproline is associated with various diseases. High performance liquid chromatography methods, in which ultraviolet and electrochemical detectors were used, were developed and validated for the determination of hydroxyproline in urine. Both methods included acid hydrolysis and derivation. The most appropriate time, temperature and pH were identified to optimize derivatization processes. Limits of detection were calculated as 1.57 mu g/mL, 0.9 mu g/mL and limits of quantification were 4.76 mu g/mL, 2.73 mu g/mL for UVD and ECD methods, respectively. Precision and accuracy of the methods were obtained <= 10.9 % (RSD), <= 11.5% (RE). The recoveries were found 108 +/- 6% and 102 +/- 7% for UVD and ECD methods, respectively. A strong, positive and linear correlation was found between hydroxyproline values obtained from UVD and ECD methods (p<0.01, r=+0.98). After optimization and validation of these methods, OHP levels in urine samples which were obtained from non-smokers and smokers were analyzed and, observed OHP/creatinine levels were compared. Results of both methods showed that total urinary OHP values of smokers were significantly higher than non-smokers (p<0.05).
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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.