Showing papers by "Sezgin Bakırdere published in 2019"

Simultaneous Determination of Fluoxetine, Estrone, Pesticides, and Endocrine Disruptors in Wastewater by Gas Chromatography–Mass Spectrometry (GC–MS) Following Switchable Solvent–Liquid Phase Microextraction (SS–LPME)

Abstract: A simple and sensitive analytical method for the determination of fluoxetine, estrone and selected pesticides and endocrine disruptors has been proposed for wastewater analysis by gas chromatography–mass spectrometry (GC–MS). A switchable solvent was produced with N,N-dimethylbenzylamine by changing its hydrophobic properties by the addition of CO2 for protonation. Sodium hydroxide was added to switch the solubility of the extraction solvent and to allow phase separation in the sample/standard medium. Analytical parameters affecting the extraction outputs such as volume of switchable solvent, concentration and volume of sodium hydroxide, mixing type and period were investigated to improve the extraction recovery of the selected analytes. Under the optimum conditions, limits of detection and limits of quantification for the analytes were calculated in the ranges of 0.16–8.6 ng mL−1 and 0.54–29 ng mL−1, respectively. The developed method was successfully applied to synthetic wastewater and two munic...

A rapid and sensitive reversed phase-HPLC method for simultaneous determination of ibuprofen and paracetamol in drug samples and their behaviors in simulated gastric conditions.

Abstract: Paracetamol is a widely used drug for fever and pain relief. Ibuprofen is a common nonsteroidal anti-inflammatory drug. In this study, a sensitive and accurate reversed phase high performance liquid chromatography method was developed for the simultaneous determination of ibuprofen and paracetamol. The chromatographic separation was achieved on a Phenomenex C18 (250 mm, 4.6 mm, 5 μm) column. Fifty milli molar phosphate buffer (pH 7.5) and methanol were used as mobile phase in a gradient elution mode. The retention times of paracetamol and ibuprofen were 5.7 and 10.4 min, respectively. The linearity of the developed method was established in the range of 0.25 - 250 mg/L with a correlation coefficient of 0.9998 for both analytes. The limit of detection/quantification values were found to be 0.06/0.19 and 0.08/0.26 mg/L for ibuprofen and paracetamol, respectively. The method was successfully applied in drug samples in the form of tablets and suspensions. The calculated concentrations matched with the claimed values on their prospectuses. The drug samples were studied under simulated gastric conditions to determine the behaviors of the analytes in the human body. The obtained results showed no change in the retention time of the analyte peak shapes throughout the 210 minutes.

Application of supercritical gel drying method on fabrication of mechanically improved and biologically safe three-component scaffold composed of graphene oxide/chitosan/hydroxyapatite and characterization studies

Abstract: Multicomponent-porous scaffolds have recently gained much attention in bone tissue engineering applications due to their ability to mimic the composite structure of natural bone tissue. In the present study, it was aimed to fabricate biologically safe and mechanically improved three-component scaffolds for bone tissue engineering applications. This is the first original report on the application of supercritical gel drying for the fabrication of three-component scaffolds composed of graphene oxide (GO) synthesized by Improved Hummers Method, chitosan (CS) and hydroxyapatite (HAp) derived from eggshells. The phase, morphology, mechanical property and in-vitro biocompatibility of scaffolds were investigated by FTIR, XRD, SEM, TEM, BET, TGA, Universal Instron Mechanical Test System, and MTT testing. For the preparation of scaffolds, GO, CS and HAp solutions were blended at various ratios. Resulting mixtures were molded, frozen, exposed to water-acetone substitution procedure, and dried by supercritical gel drying, respectively. Then, dried scaffolds were subjected to MTT testing for cytotoxicity analysis to examine toxicity effect of GO. Results revealed dose-dependent cytotoxicity effect of GO on MC3T3-E1 cell line. The highest relative cell viability was observed with three-component scaffold composed of GO:1 wt%, CS:39 wt% and HAp:60 wt%. According to characterization studies, this original report demonstrated that scaffold produced with the mentioned procedure had a three-dimensional porous sponge-like structure, highest relative cell viability, and increased mechanical compressive strength compared to other scaffolds fabricated. These properties enable scaffold with combined improvement in biological and mechanical properties to be a promising candidate for application in bone tissue materials.

Accurate and sensitive determination of sildenafil, tadalafil, vardenafil, and avanafil in illicit erectile dysfunction medications and human urine by LC with quadrupole‐TOF‐MS/MS and their behaviors in simulated gastric conditions

Abstract: The widespread use of phosphodiesterase-5 inhibitors has attracted broad attention of counterfeiters to develop illicit erectile products with inaccurate amounts, unknown toxicity, and purity of active ingredients. Correspondingly, intake of these products endangers consumer health and needs to be screened for precautionary actions to reduce this risk. Therefore, in this study, a sensitive and rapid analytical method has been developed for simultaneous determination of selected phosphodiesterase-5 inhibitors present in illicit erectile medications and human urine. Quantification of the analytes was performed by liquid chromatography coupled with quadrupole-time-of-flight tandem mass spectrometry system. The chromatographic separation was successfully achieved with a run period of 8 min. Low detection limits were obtained in the range of 1.63-9.81 ng/g with relative standard deviations below 7.72% obtained using the replicate measurements of lowest concentration in calibration plots. The analytical performance of the proposed method proved good linearity, low detection limits, good accuracy and precision with high percent recoveries for human urine samples. Developed method was successfully applied to real samples including four different brands of illicit erectile medications. The results obtained revealed the presence of high levels of sildenafil in analyzed samples. The behaviors of selected phosphodiesterase-5 inhibitors were also studied in simulated gastric conditions.

Accurate and Sensitive Determination Method for Procymidone and Chlorflurenol in Municipal Wastewater, Medical Wastewater and Irrigation Canal Water by GC–MS After Vortex Assisted Switchable Solvent Liquid Phase Microextraction

Abstract: In this study, the detection power of a gas chromatography mass spectrometer (GC–MS) for procymidone and chlorflurenol was significantly enhanced using switchable solvent liquid phase microextraction (SS-LPME) as a preconcentration tool. This was achieved by a comprehensive optimization of significant parameters to the SS-LPME method such as switchable solvent amount, concentration and amount of sodium hydroxide, pH effect and mixing effect. The optimum experimental conditions obtained were used to determine analytical figures of merit for the analytes. The limits of detection obtained were 0.44 and 2.9 ng/mL for procymidone and chlorflurenol, respectively. The optimum method was applied to water sampled from an irrigation canal and two wastewater samples. The samples were spiked at two concentrations and the percent recovery results obtained ranged between 86 and 115% for both analytes. The recovery results together with the low standard deviations recorded validated the method as accurate and precise.

Simultaneous Determination of Chromium Species in Water and Plant Samples at Trace Levels by Ion Chromatography–Inductively Coupled Plasma-Mass Spectrometry

Abstract: Ion chromatography–inductively coupled plasma-mass spectrometry (IC–ICP-MS) was used for the identification and quantification of chromium species. Chromium(III) and chromium(VI) were separated and...

Experimental Design of Switchable Solvent-Based Liquid Phase Microextraction for the Accurate Determination of Etrimfos From Water and Food Samples at Trace Levels by GC-MS

Abstract: Presented in this study is a simple but efficient switchable polarity solvent microextraction strategy for etrimfos preconcentration from water and food samples for quantification by gas chromatography mass spectrometry. Repeatability of the extraction process and instrumental measurements were enhanced by using deuterated bisphenol A as internal standard. Significant parameters of the extraction method were fitted into an experimental design model to study the effects of parameters on extraction output, as well as mutual effects of combined parameters. The design model was formed with 51 experimented data obtained from the combination of sodium hydroxide volume, switchable solvent volume, and vortex period at three levels. The method was validated by applying optimum conditions attained from the model predictor. The detection limit was found to be 1.3 ng/mL and it corresponded to an enhancement factor of about 54 folds when compared to direct GC-MS measurement. Etrimfos was not detected in the water and food samples tested but the results (92–107%) obtained from spiked recovery experiments established that etrimfos when present in the selected matrices can be accurately and precisely quantified.

Magnetic cobalt particle-assisted solid phase extraction of tellurium prior to its determination by slotted quartz tube-flame atomic absorption spectrophotometry

Abstract: The emergence of magnetic materials has opened up doors to numerous applications including their use as sorbents for preconcentration of trace elements. Magnetic materials exhibit many unique advantages in sample preparation such as easy separation from the sample, high preconcentration factor, and short operation period. In the present study, magnetic cobalt material was synthesized, characterized, and used as an effective sorbent in a solid phase extraction process. Experimental variables of the extraction process including pH and volume of buffer solution, eluent concentration and volume, mixing type and period, and sorbent amount were optimized to achieve maximum extraction efficiency. Instrumental variables of flame atomic absorption spectrophotometry and the type of slotted quartz tube were also investigated. Under the optimum conditions, the combined method provided a wide linear range between 50 and 200 ng/mL with detection and quantification limits of 15.4 ng/mL and 51.3 ng/mL, respectively. Relative standard deviations of the proposed method were less than 5.0% and a high enrichment factor of 86.7 was obtained. The proposed method was successfully applied to soil samples for the determination of trace tellurium.

Evaluation of magnetic field assisted sun drying of food samples on drying time and mycotoxin production

Abstract: Mycotoxins are a variety of metabolic products produced by fungi, which can cause various damages to other organisms. The aim of this study was to figure out the effect of new drying methods namely “drying in oven under magnetic field” and “drying under the sun and magnetic field” on the mycotoxin formation for some food samples. In this system, a fixed magnetic field of 300 μT was used for the drying process. The amounts of moisture in the samples dried with the new developed methods were measured in hazelnut (Corylus L.), fig (Ficus carica L.), chili pepper (Capsicum annuum L.) and grape (Vitis vinifera L.) depending on time. Mycotoxin species within different foodstuffs were determined at trace levels by using LC-MS/MS device under the optimum conditions, and the results obtained from the samples dried with the new methods were compared with each other and results of food samples dried by traditional method. The results indicated that the new developed drying methods cause decrease in the drying periods, and the dried samples did not contain any mycotoxin. This study suggested new drying strategies to eliminate the mycotoxin formation. For the analysis of the results, different statistical tests were used. In order to determine which technique works faster in drying the samples, box plots were obtained using descriptive statistics. Mann Whitney tests were also applied to determine if there was a statistical difference between the drying methods.

Sensitive and Accurate Determination of Cobalt at Trace Levels by Slotted Quartz Tube-Flame Atomic Absorption Spectrometry Following Preconcentration with Dispersive Liquid–Liquid Microextraction

Abstract: Slotted quartz tube-flame atomic absorption spectrometry (SQT-FAAS) was used as a sensitive technique for the determination of cobalt, an element has toxic effects on living organisms at hi...

Accurate, sensitive, and precise determination of cobalt in soil matrices by the combination of batch type gas-liquid separator-assisted photochemical vapor generation and atomic absorption spectrophotometry

Abstract: Determination of cobalt at low concentrations is an important issue because of its potential harmful effects on human health. Although flame atomic absorbance spectrometry (FAAS) is a fast and cheap method, it has high detection limits compared to other methods due to low nebulizer efficiency. In this study, the sensitivity, accuracy, and precision of the conventional FAAS were tried to be improved for cobalt determination using a photochemical vapor generation (PVG) system equipped with a batch type gas-liquid separator (BTGLS). The system parameters including organic acid type and concentration, UV irradiation period, mixing type, atomizer temperature, carrier gas flow rate, and sample volume were optimized to improve the detection power. The limits of detection and quantification were found to be 8.7 and 28.9 μg L−1, respectively. The low relative standard deviation results indicated high precision. Applicability and accuracy of the method to soil samples was determined by recovery studies and percent recoveries were obtained between 98.9–107.0%.

Determination of palladium in soil samples by slotted quartz tube-flame atomic absorption spectrophotometry after vortex-assisted ligandless preconcentration with magnetic nanoparticle–based dispersive solid-phase microextraction

Abstract: In this study, a rapid and effective dispersive solid-phase microextraction (d-SPME) method was developed to preconcentrate Pd from aqueous extract of soil samples by slotted quartz tube-flame atomic absorption spectrometry (SQT-FAAS). The unique properties of magnetic nanoparticles (MNPs) were used to directly isolate Pd from the sample solutions without the need for complexation. Significant parameters of the extraction method such as magnetic nanoparticle type and amount, pH and amount of buffer solution, amount of eluent, and mixing type and period were optimized together with other instrumental parameters to boost the absorbance signal of Pd. An SQT was fitted onto the burner head to boost the interaction between Pd atoms and hollow cathode lamp radiation to enhance absorbance signals. The limit of detection (LOD) and limit of quantification (LOQ) values for Pd determined (d-SPME-MNP-SQT-FAAS) were 6.4 and 21.4 ng/mL, respectively. The percentage relative standard deviation of the developed method was calculated as 6.6%. The method was applied to soil samples taken from the campus area and spiked recovery experiments were performed to evaluate the method’s accuracy/applicability. Satisfactory percent recovery results (90–101%) were obtained for different spiked concentrations and this proved the accuracy/applicability of the method.

Simultaneous determination of drug active compound, hormones, pesticides, and endocrine disruptor compounds in wastewater samples by GC-MS with direct calibration and matrix matching strategies after preconcentration with dispersive liquid-liquid microextraction

Abstract: DLLME was coupled with GC-MS for the simultaneous determination of a drug active compound, hormones, pesticides, and endocrine disruptor compounds with high accuracy and reproducibility in this study. Extraction parameters that affect extraction output including types and volumes of dispersive and extraction solvents, and effect of salt addition were optimized to lower the detection limits for 12 compounds. Under the optimum conditions, LOD and LOQ values were found between 1.99–5.05 and 6.63–16.87 ng/mL, respectively. Spiked recovery tests were also applied to wastewater samples to check the applicability of the method. Matrix matching strategy was used to improve the overall recovery results of the analytes obtained for municipal wastewater. Two different municipal wastewater samples were used in the matrix matching studies. Percent recovery values calculated with the matrix matching experiments were between 85–114%. The results obtained indicated that the developed method could be applied for the determination of the analytes of interest with high accuracy and sensitivity.

Determination of Bismuth in Bottled and Mineral Water Samples at Trace Levels by T-Shaped Slotted Quartz tube-Atom Trap-Flame Atomic Absorption Spectrometry

Abstract: An accurate and reliable analytical method for the determination of bismuth at trace levels in bottled and mineral water samples has been developed based on hydrogen assisted T-shape slotted quartz...

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.

Abstract: 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 μg 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.