Hasan Ertaş

Determination of mercury in table salt samples by on-line medium exchange anodic stripping voltammetry.

A new method for the determination of traces of total mercury by using a gold film electrode in salt samples was developed. Table salts are known to contain mercury at ultra-trace level as well as a high quantity of chloride ions that cause severe disturbance during the stripping step when gold is used as the electrode material in voltammetric measurements. The interference of high chloride content in the determination of mercury was eliminated by reducing its concentration down to 3 x 10(-3) mol L(-1) level which is optimum for the determination by using on-line medium exchange procedure immediately after the deposition step. The deposition potential applied to the electrode was maintained at 0.2 V (vs. Ag/AgCl double junction electrode) while the cell content was sucked by a pump and replaced with fresh electrolyte simultaneously. The analyte loss resulted from the air contact of the electrode was prevented by this means. The mercury ions present in the salt samples were collected at +0.2 V for 60 s, the electrolyte was replaced by 0.1 mol L(-1) HClO4 and the potential was scanned, attaining a detection limit of 0.17 microg L(-1), with R.S.D. of 1.2% (S/N=3). The recovery of the method was 94.6%. The performance and accuracy of the method was compared with that of atomic fluorescence spectrometry (AFS). Consequently, this developed method can offer a wide range of application in saline samples.

A novel polythiophene – ionic liquid modified clay composite solid phase microextraction fiber: Preparation, characterization and application to pesticide analysis

This report comprises the novel usage of polythiophene - ionic liquid modified clay surfaces for solid phase microextraction (SPME) fiber production to improve the analysis of pesticides in fruit juice samples. Montmorillonite (Mmt) clay intercalated with ionic liquids (IL) was co-deposited with polythiophene (PTh) polymer coated electrochemically on an SPME fiber. The surface of the fibers were characterized by using scanning electron microscopy (SEM). Operational parameters effecting the extraction efficiency namely; the sample volume and pH, adsorption temperature and time, desorption temperature and time, stirring rate and salt amount were optimized. In order to reveal the major effects, these eight factors were selected and Plackett-Burman Design was constructed. The significant parameters detected; adsorption and temperature along with the stirring rate, were further investigated by Box-Behnken design. Under optimized conditions, calibration graphs were plotted and detection limits were calculated in the range of 0.002-0.667ng mL(-1). Relative standard deviations were no higher than 18%. Overall results have indicated that this novel PTh-IL-Mmt SPME surface developed by the aid of electrochemical deposition could offer a selective and sensitive head space analysis for the selected pesticide residues.

Preparation and characterization of sodium dodecyl sulfate doped polypyrrole solid phase micro extraction fiber and its application to endocrine disruptor pesticide analysis.

A robust in house solid-phase micro extraction (SPME) surface has been developed for the headspace (HS)-SPME determination of endocrine disruptor pesticides, namely, Chlorpyrifos, Penconazole, Procymidone, Bromopropylate and Lambda-Cyhalothrin in wine sample by using sodium dodecylsulfate doped polypyrrole SPME fiber. Pyrrole monomer was electrochemically polymerized on a stainless steel wire in laboratory conditions in virtue of diminishing the cost and enhancing the analyte retention on its surface to exert better selectivity and hence the developed polymerized surface could offer to analyst to exploit it as a fiber in headspace SPME analysis. The parameters, mainly, adsorption temperature and time, desorption temperature, stirring rate and salt amount were optimized to be as 70°C and 45min, 200°C, 600rpm and 10gL(-1), respectively. Limit of detection was estimated in the range of 0.073-1.659ngmL(-1) for the pesticides studied. The developed method was applied in to red wine sample with acceptable recovery values (92-107%) which were obtained for these selected pesticides.

Development of a gas chromatographic method for the determination of Chlorpyrifos and its metabolite Chlorpyrifos-oxon in wine matrix

A reliable method has been developed for the determination of Chlorpyrifos (CP) and its metabolite Chlorpyrifos-oxon (CPO) in wine sample using pulsed splitless technique coupled with gas chromatography by using electron capture detector. In this study, a quick, easy and cheap sample preparation method (QuEChERS) based on liquid extraction with acetonitrile, followed by dispersive solid phase extraction using primary secondary amine was tested for the separation and quantification of CP and CPO in wine samples. The accuracy of the developed method was tested upon recovery studies and it was calculated as (92.3 ± 18.2)% for CP and (96.6 ± 16.1)% for CPO. LOD and LOQ values of CP were found as 0.04 and 0.15 ng/mL and 0.49 and 1.62 ng/mL for CPO respectively. By using the pulsed splitless injection mode, the sensitivity of the determination of CP and its metabolite CPO in wine samples was improved compared to splitless technique. CP content of analyzed wine sample was found as 2.05 ± 0.15 ng/mL with a RSD of 7.6% and CPO content was found as 4.99 ± 0.15 ng/mL with a RSD of 3.0% (n=3). The expanded measurement uncertainties were calculated as 17% and 6% for CP and CPO, respectively.

Assessment of DFG-S19 method for the determination of common endocrine disruptor pesticides in wine samples with an estimation of the uncertainty of the analytical results.

A gas chromatographic method for the determination of endocrine disruptor pesticides (Chlorpyrifos, Penconazole, Procymidone, Iprodione, Bromopropylate and Lambda-Cyhalothrin) in wine samples is described. A general DFG-S19 method for residual pesticide determination in all kind of food stuff was investigated to simplify and adopt for wine samples in this work. Alternative sample preparation routes were elucidated and compared according to their recovery values. Four different separation techniques were tested and the method employing florosil column after a LLE procedure was applied for wine samples with satisfactory recovery ratios (72-97%). The pesticides were extracted from the sample by cyclohexane-ethyl acetate mixture (1:1 v/v) and cleaned up by florosil column. The regression coefficients were at least 0.99 and relative standard deviations were no higher than 16%. Detection limits were in the range of 0.6-2.9 ng/mL and the relative expanded measurement uncertainties were calculated in the 7-22% range.

Head space voltammetry: A novel voltammetric method for volatile organics and a case study for phenol

Present paper describes the results of a novel method which combines the Head space (HS) preconcentration of the analyte on the electrode prior to the voltammetric analysis. Thereafter, the method was called HS-Voltammetry. The performance of the method was tested upon using an electroactive and volatile molecule, phenol molecule, which gives an oxidation peak at conventional electrodes. In this study, a glassy carbon electrode was modified with polypyrrole by electropolymerization and then, the electrode was placed over the solution in a sealed vial heated gently on a hotplate with a stirrer for phenol determination. By controlling the thickness of the polymeric coating and optimizing preconcentration parameters such as vial pH and temperature, stirring rate and exposure time, a very consistent (5.2% at 5.0×10(-7) M) fraction of the analyte can be extracted during a predetermined time. The oxidation peak current at 0.8 V depended linearly on the phenol concentration over a wide range (3 orders of magnitude). The detection limit was estimated as 7.0×10(-8) M at 60 °C (S/N=3) which is well below the limit set by the European Community for phenols in wastewaters (ca. 5×10(-6) M). The effect of other phenolic compounds was also examined and it was shown that head space preconcentration eliminated the interference of non-volatile phenolic acids studied. For volatile phenolic compounds, the selectivity can be maintained in cases when isolated peaks are obtained for each component. The proposed method has been applied successfully for the determination of phenol in artificial wastewater and recovery percentage was calculated as 93%.

Prevalence of Alcohol in Blood Samples from Traffic Accident Cases in Turkey

Alcohol is one of the main causes of traffic accidents worldwide. With a population of 70 million, 12 million vehicles, and 18 million drivers (16% women), Turkey is one of the European countries that has a high incidence of road traffic accidents.In accordance with Turkish laws, subjects were considered to be positive when alcohol blood concentration exceeded 50 mg/100 mL. The objective of the present study was to obtain reliable and comparable data about alcohol use in traffic cases in Turkey. All cases are admitted to the emergency department at Ege University Medical Faculty. The cases from police officers are described as traffic control cases. Alcohol was detected in the blood of about 54.4% of the traffic-related cases during October 2005 to March 2007. It has been observed that, in 17.4% of the traffic accident cases, the blood alcohol level was 50 mg/dL or less, which is the legal limit in Turkey for car drivers. Alcohol prevalence was 57.2% in male cases and 43.6% in female cases. In alcohol-positive cases; the ratios for males were 1.73 times more frequent in traffic-related cases. Prevalence data will help traffic safety professionals to adequately allocate resources and plan future efforts in reducing drinking-and-driving behavior and thereby reduce traffic accidents.

Gas chromatographic analysis of alcohols in blood with a chemometric approach

The objective of the present study is to examine the main and interactive effects of different factors related with headspace-solid phase extraction (HS-SPME) and gas chromatography (GC) conditions for the simultaneous determination of alcohols (ethanol, methanol, isopropanol, n-propanol) and acetone in blood samples. In order to evaluate the simultaneous effects of the significant variables, a chemometric approach was utilized to reveal the important parameters. The factors affecting the headspace extraction of alcohols on the SPME fiber was first deduced in a screening study by applying a Plackett–Burman design. According to the screening results, the factors that possess a positive effect on peak areas are sample concentration, inlet temperature, flow rate for the carrier gas and volume of the solution. Based on the results of the screening study, to continue optimization, six insignificant values were fixed at the appropriate amounts (oven temperature: 50 °C; detector temperature: 250 °C; H2 gas flow rate: 35 mL min−1; split flow rate: 30 mL min−1; equilibrium temperature: 55 °C, extraction time: 4 min). Subsequently, a central composite design (CCD) was constructed for optimization and response surface methodology (RSM) was used to interpret the effect of each pair of independent variables on the response. The optimized method for alcohol and acetone analysis via HS-SPME-GC was validated through spike recovery tests.

Classification of olive oils using chromatography, principal component analysis and artificial neural network modelling

Classification and addressing, and geographical origin of different olive oils is of great importance due to their differentiation in quality, and for commercial concerns. In this study, quantification of sterols, fatty acids, and triacylglycerol composition of forty-nine olive oils collected from six different locations of western part of Turkey (İzmir, Manisa, Aydın, Muğla, Bursa, and Edremit Bay) were performed by using chromatographic methods. Data for those olive oil samples were compiled, and classified with the artificial neural network (ANN) modelling and principal components analysis (PCA). The analytical results included resourceful information about determining geographical origin and traceability of olive oil in Turkey by using ANN and PCA. The ANN model for sterol composition showed the highest accuracy with 85.71%. The FAME and TAG profiles followed this with 83.67 and 81.63% accuracy respectively. However, İzmir and Manisa regions have poor sensitivity values with all ANN models since they are geographically very close to each other. Furthermore, the PCA results of the sterol composition have provided separation and clustering between locations. β-sitosterol, campesterol, stigmasterol and 24-metilen cholesterol have an important role in determining the separation of the locations of origin. While separation of the Bursa location has been under the pressure of FAME composition, the TAGs have been effective on the clustering of the Aydın and Edremit Bay. In conclusion, the geographical authentication of Turkish olive oils can be done with high accuracy by using ANN and PCA.

Determination of trace elements and stable carbon isotope ratios in virgin olive oils from Western Turkey to authenticate geographical origin with a chemometric approach

In this study, trace element contents and stable carbon isotope ratios of olive oils were determined to evaluate their potential as authentication parameters. Forty-nine virgin olive oil samples (VOOs) from six different locations of the western part of Turkey (İzmir, Manisa, Aydın, Muğla, Bursa and Edremit Bay) were analysed with ICP-MS and EA-IRMS. V, Mn, Ni, Cu, Ba, Na, K, Ca, Fe, Mg, Pb, As, Co, Cr and Zn were found in the olive oil samples and determined δ13C stable istope ratios. Data from the olive oil samples were compiled and classified with chemometric approach. The results showed that there is significant potential to successfully authenticate olive oils according to Fe and Zn on the Manisa and δ13C have dominant effect on the location of Edremit Bay. As a result, the outcome of this study could be used to identify the geographical origin of olive oils especially for the Manisa and Edremit Bay locations.