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Öğe Capillary electrophoresis in metabolomics(Elsevier Sci Ltd, 2006) Ramautar, Rawi; Demirci, Ayla; de Jong, Gerhardus J.This article describes the potential of capillary electrophoresis (CE) in metabolomics, which concerns the comprehensive analysis of endogenous low-molecular weight compounds in a biological system. Consequently, metabolomic methods are often developed to separate and to detect as many endogenous metabolites as possible in a single analysis. CE is a very powerful technique for this type of profiling. We demonstrate the applicability of CE in different fields of metabolomics research. We show illustrative clinical, bacterial and plant examples and stress the information that CE systems obtain. We distinguish between targeted and non-targeted metabolomic studies in the bacterial and plant sections. We discuss general aspects of sample preparation of CE for biological samples, and pay special attention to the potential of CE-mass spectrometry in metabolomics. We also discuss future developments with regard to sample preparation and the use of hyphenated systems. (c) 2006 Elsevier Ltd. All rights reserved.Öğe Determination of polycyclic aromatic hydrocarbons in cigarette filter tar by means of hollow-fiber liquid phase microextraction-HPLC-UV system(Taylor & Francis Inc, 2013) Demirci, Ayla; Alver, ErolA high-pressure liquid chromatographic method was developed to determine polycyclic aromatic hydrocarbons (PAHs) in cigarette filter tar using hollow fiber-liquid-phase microextraction (HF-LPME) for the clean-up and enrichment steps. The donor phase for HF-LPME is a mixture of acetonitrile and water. Before analyzing real cigarette samples, some preliminary experiments were necessary to find the optimum starting HF-LPME conditions, including donor phase composition (acetonitrile/water), pH, acceptor phase type, mixing rate, and extraction time. These experiments were performed with model PAH solutions. The chromatographic analysis of the acceptor solution was performed using a C18 reversed-phase column and a UV detector system. Under optimum conditions, percent recoveries and enrichment factors ranged from 63 to 97% and from 208 to 320, respectively, for model PAH solutions. The recoveries from real samples were between 8 and 71%, whereas the enrichment factors ranged from 27 to 234. The limit of detection (LOD) of the six PAHs was found to be between 0.040 and 0.136ngmL1. The concentrations of the six PAHs in real samples (various brands of cigarettes) were determined. The total amounts of PAHs (six) found in the filter tar of the three brands filter tar were 165.49, 50.49, and 51.04ng/cigarette, respectively.Öğe Factorial Design Optimization of Solid-Phase Microextraction for High-Performance Liquid Chromatography-Ultraviolet Spectrometry Analysis of Polycyclic Aromatic Hydrocarbons in Cigarette Filter Tar(Taylor & Francis Ltd, 2014) Demirci, AylaA simple and rapid procedure for the determination of polycyclic aromatic hydrocarbons (PAHs) in cigarette filter tar using solid-phase microextraction (SPME) was developed. The analysis was carried out using high-performance liquid chromatography equipped with an ultraviolet detector. The effects of the SPME experimental parameters on the extraction recovery were studied simultaneously using a central composite design (CCD) after a 2(6-2) fractional factorial experimental design. The SPME variables of interest were the extraction temperature, the extraction time, and the stirring speed, as well as the pH and the concentrations of NaCl (%, w/v) and acetonitrile (ACN). The optimal SPME conditions were as follows: an extraction temperature of 65 degrees C, an extraction time of 50min, a stirring speed of 800rpm, 0% NaCl (w/v), 10% ACN in the sample, and a source pH of 8.0. The extraction calibration plots were linear over the range of 0.25-20ng mL(-1) (r(2) > 0.9912) and the limits of detection (LODs) for the 6 PAHs studied were from 0.17-5.02ng cigarette(-1). The relative standard deviation (RSD) ranged from 7.1-13.5% for intra-day variation and from 8.5-18.4% for inter-day variation. The performance of the proposed method was evaluated for extraction and determination PAHs in real samples (various brands of cigarettes). The total amounts of all of the studied PAHs found in the filter tar of the three brands of cigarettes were 320.2, 17.9, and 66.7ng cigarette(-1), respectively.Öğe MICROEXTRACTION METHODS(Yildiz Technical Univ, 2012) Alver, Erol; Demirci, Ayla; Ozcimder, MustafaAccurate, rapid and economic qualitative and quantitative analysis of trace amount substances in biological, environmental and food products is an important issue. Mostly, such substances must be taken from the matrix (separation) and concentrated (enrichment) before determining with analytical equipment. For these processes liquid-liquid, solid-liquid extraction and solid phase extraction are commonly used. However these methods are recently replaced by microexraction methods minimizing organic solvent consumption, simplifying sample preparation steps, providing high enrichment rates and appropriate to automation.Öğe Statistical Classification of Cigarettes Using High Pressure Liquid Chromatograms of Cigarette Filter Tar as Fingerprint(Asian Journal Of Chemistry, 2013) Demirci, Ayla; Ekiz, MeltemIn this work, we have showed that a liquid chromatogram can be used as finger print to characterize and classify cigarettes. A liquid chromatographic (high pressure liquid chromatography) procedure was first developed to obtain chromatograms of different cigarettes. The cellulose filter of a smoked cigarette was first dissolved in 5 mL acetonitrile. Then the organics were partitioned into the n-hexane phase. After concentrating the n-hexane phase to 100 mu L, 5 mu L was injected to a high pressure liquid chromatography. The chromatograms were obtained using a C18 reversed phase column. The mobile phase was 80 % acetonitrile/water with 1 mL min(-1). The detector was UV spectrometer working at 254 nm. For the evaluation the chromatograms as fingerprints, five peaks were chosen randomly. The heights of the corresponding peaks were used for the statistical evaluation which was based on the discriminate analysis for classifying problems introduced by Anderson. To achieve this, a Matlab computer program was developed. The proposed method can be performed in a relatively short time.
