Showing papers by "Sezgin Bakırdere published in 2016"

Development of a sensitive liquid–liquid extraction method for the determination of N-butyryl-L-homoserine lactone produced in a submerged membrane bioreactor by gas chromatography mass spectrometry and deuterated anthracene as the internal standard

Abstract: Quorum sensing is defined as the bacterial communication through sending and receiving chemical signals such as N-acyl homoserine lactone (AHL) and oligopeptide for Gram negative bacteria and Gram positive bacteria, respectively. This mysterious bacterial interaction regulates a wide range of activities affecting the environment, agriculture, and therefore, humans. In the last century, quorum sensing investigations trying to follow and measure these chemical signals have accelerated. In this study, an analytical method was developed and optimized in order to extract and measure one of the AHLs: N-butyryl-L-homoserine lactone (C4-HSL) by gas chromatography-mass spectrometry (GC-MS). The aim of the study was to develop a method that increases the sensitivity and precision of AHL detection by GC-MS due to the problem in the determination of analytes in wastewater which have a complex matrix. The limits of detection and quantification obtained for C4-HSL were 12.9 ng mL−1 and 43.3 ng mL−1, respectively. The precision of the method was improved upon using deuterated anthracene as the internal standard, which gave a lower relative standard deviation compared to that without the internal standard.

Determination of Lead in Drinking and Wastewater by Hydride Generation Atomic Absorption Spectrometry

Abstract: This work describes the optimization of hydride generation atomic absorption spectrometry for the determination of lead at trace concentrations. The parameters affecting the production, transport, and atomization of plumbane in a closed vessel were optimized. The concentrations of reagents affecting the generation of the lead hydride were also optimized to obtain high hydride generation efficiency. The atomization temperature, reaction period, pump speed, pump period, and flow rates of reducing agent and carrier gas were varied to maximize the sensitivity for lead. The accuracy of the method was evaluated by the analysis of certified reference materials. The method provided a linear dynamic range for lead from 2.0 to 40 µg/L with a limit of detection of 0.56 µg/L.

A Novel Liquid–Liquid Extraction for the Determination of Nicotine in Tap Water, Wastewater, and Saliva at Trace Levels by GC-MS

Abstract: Determination of nicotine at trace levels in different matrixes is crucial because of nicotine's strongly addictive property. In this study, a simple and fast analytical method was developed using liquid- liquid extraction with GC-MS. Chloroform was used as an extraction solvent. Different parameters for extraction, such as pH of the solution, types and volumes of extraction and supporter solvents for dispersion, extraction period, and salt type and its amount, were optimized. To improve the precision, naphthalene was used as an internal standard. The calibration plot of nicotine was linear from 0.010 to 2.0 mg/L with a correlation coefficient 0.9996. The LOD and LOQ for nicotine after extraction were 2.6 and 8.8 ng/mL, respectively. Under the optimum conditions, tap water, wastewater, and saliva samples were analyzed for their nicotine content. The spiking experiments yielded satisfactory recoveries of 97.6 ± 3.5, 96.8 ± 1.1, and 85.1 ± 1.3% for tap water, wastewater, and saliva samples, respectively.

A simple design for microwave assisted digestion vessel with low reagent consumption suitable for food and environmental samples

Abstract: The objective of this work is to prepare a cost-effective, low reagent consumption and high performance polytetrafluoroethylene (PTFE) vessel that is capable to work in domestic microwave for digesting food and environmental samples. The designed vessel has a relatively thicker wall compared to that of commercial vessels. In this design, eight vessels are placed in an acrylonitrile butadiene styrene (ABS) holder to keep them safe and stable. This vessel needs only 2.0 mL of HNO3 and 1.0 mL H2O2 to digest 100 mg of biological sample. The performance of this design is then evaluated with an ICP-MS instrument in the analysis of the several NIST standard reference material of milk 1849a, rice flour 1568b, spinach leave 1570a and Peach Leaves 1547 in a domestic microwave oven with inverter technology. Outstanding agreement to (SRM) values are observed by using the suggested power to time microwave program, which simulates the reflux action occurring in this closed vessel. Taking into account the high cost of commercial microwave vessels and the volume of chemicals needed for various experiments (8–10 mL), this simple vessel is cost effective and suitable for digesting food and environmental samples.

Speciation of Arsenic in Fish by High-Performance Liquid Chromatography-Inductively Coupled Plasma-Mass Spectrometry

Abstract: Arsenic speciation in fish was performed using isocratic elution with cation exchange column high-performance liquid chromatography and inductively coupled plasma-mass spectrometry detection. The separation of arsenobetaine and dimethylarsinic acid was performed in 12 min. DOLT-4 dogfish liver and NIST RM-50 albacore tuna certified reference materials were used to evaluate the accuracy for the determination of total arsenic in fish. In addition, reference materials were analyzed for arsenobetaine and dimethylarsinic acid, although they were not certified for these analytes. The limits of detection for arsenic in arsenobetaine and dimethylarsinic acid were 0.20 and 0.33 ng/mL, and the limits of quantitation were 0.58 and 1.11 ng/mL, respectively. Total arsenic and arsenic species were determined in fish using the developed method. The predominant arsenic species was arsenobetaine; the measured concentrations were from 0.43 to 12.0 mg/kg arsenic as arsenobetaine. Dimethylarsinic acid concentrations ...

Determination of contamination levels of Pb, Cd, Cu, Ni, and Mn caused by former lead mining gallery

Abstract: In the present study, levels of metal contamination caused by former lead mining area were figured out. For this purpose, Pb, Cd, Cu, Ni, and Mn were determined not only in sediment samples taken from different places of the mining area but also in some plants taken around the mining place. In the digestion of plant samples, dry ashing procedure was applied. Flame atomic absorption spectrophotometer (FAAS) was used in the determination of analytes of interest. All the parameters in digestion and detection procedures were optimized to obtain efficient digestion and high sensitivities for analytes. Standard addition and direct calibration methods were applied to find whether there was any matrix interference to affect the determination of analytes. Mn concentration was found to be the highest for each sample analyzed. Lead concentration was found to be between 41 and 249 mg/kg in soil/sediment samples and between 2.2 and 1003 mg/kg in plant samples. The highest contamination levels for all of the analytes with the exception of Cd were found in current sediment sample.

Simultaneous Determination of Sildenafil and Tadalafil in Legal Drugs, Illicit/Counterfeit Drugs, and Wastewater Samples by High-Performance Liquid Chromatography.

Abstract: A sensitive analytical method was developed for the simultaneous determination of sildenafil and tadalafil in legal drugs, illicit/counterfeit drugs, and wastewater samples. Chromatographic separation of two analytes was achieved on a C18 column with a mobile phase including 50 mM phosphate buffer at pH 6.0 and acetonitrile (35 + 65, v/v) at the flow rate of 1.0 mL/min. Analytes were separated from each other in 6 min with high resolution. LOD/LOQ values were calculated as 28/92 ng/mL for sildenafil citrate and 39/129 ng/mL for tadalafil. Calibration plots for both analytes were linear with correlation coefficients >0.9993. A validated method was successfully applied to legal and illicit erectile-dysfunction drug samples consumed in Istanbul, Turkey, and to wastewater samples. Nine different samples were analyzed for qualitative and quantitative measurement of their ingredients, and the results were compared with the values written on the labels of the drugs. The wastewater sample was also analyzed for its sildenafil and tadalafil content. To calculate the recoveries, a spiking experiment was performed and recovery rates for sildenafil and tadalafil were calculated as 101.30 ± 3.43 and 102.68 ± 1.59, respectively.

Development of an analytical method for the determination of valsartan in commercial drug and sewage sludge samples by HPLC and evaluation of its stability under simulated gastric conditions

Abstract: An analytical method was developed for determination of valsartan in commercial drug and sewage sludge samples by HPLC–UV using a single wavelength (250 nm). The effect of different environmental storage conditions on the stability of valsartan was examined for a period of 85 days, after which no degradation was observed. The post oral administration stability of the valsartan was also investigated by testing valsartan under simulated gastric conditions. Results obtained showed that the structure of valsartan was conserved over 3.5-h period. The calibration plot of the study was linear over a wide concentration range with a correlation coefficient of 0.9999. The limit of detection and limit of quantitation were found to be 0.014 and 0.046 µ g mL−1, respectively. The percentage recovery of valsartan from sewage sludge was found to be 99.8%.

Study of the electron densities of some food products dried using the new method

Abstract: The main goal of this study was to determine the concentrations of P, S, Cl, K, Ca, and Sr in food samples using a newly developed drying method to find their electron densities. The methods applied to samples to find the effective drying method were as follows: “drying in oven under a magnetic field” and “drying under the sun and a magnetic field.” Concentrations of elements were determined by an energy dispersive X-ray fluorescence spectrometer soon after initial processing of dried foods. The concentrations of elements were acquired as mg/kg. An attempt was made to calculate the electron densities of the dried samples. The electron densities of food samples dried in oven under a magnetic field as the effective one were identified using ZXCOM software. This particular attempt is fairly new, and there is no information in this field. The electron density (Neff) values of the dried samples were calculated for all samples of interest. The electron densities of fig samples dried with the new method ...

Sensitive Determination of Sertraline in Commercial Drugs and Its Stability Check in Simulated Gastric Juice.

Abstract: A sensitive analytical method was developed for the determination of sertraline in commercial drug samples by using GC-MS. The selected-ion monitoring mode was used at the most sensitive m/z 274 to obtain a lower detection limit. LOD/LOQ values were obtained as 1.6/5.4 ng/mL for sertraline under the optimum conditions. The calibration plot was linear between 5.0 and 2000 ng/mL with the correlation coefficient of 0.9999. The validated method was successfully applied to three different brands of drug samples for both qualitative and quantitative measurement of sertraline. In this experiment, four replicate extractions were performed for each brand, and the results were compared to the values written on the labels of the drug brands. Spiking experiments were also performed to check the effect of the matrixes on the determination, and it was observed that there was no shift in the retention time of the analyte. In addition, simulated gastric juice experiments were performed to check the stability of sertraline in the stomach for 240 min, and it was observed that there was no change in the structure of the analyte.