Mehmet Fatih Cengiz

Elution of monomer from different bulk fill dental composite resins

OBJECTIVE The purpose of this study was to evaluate the elution of Bis-GMA, TEGDMA, HEMA, and Bis-EMA monomers from six bulk fill composite resins over four different time periods, using HPLC. METHODS Six different composite resin materials were used in the present study: Tetric Evo Ceram Bulk Fill (Ivoclar Vivadent, Amherst, NY), X-tra Fill (VOCO, Cuxhaven, Germany), Sonic Fill (Kerr, Orange, CA, USA), Filtek Bulk Fill (3M ESPE Dental Product, St. Paul, MN), SDR (Dentsply, Konstanz, Germany), EQUIA (GC America INC, Alsip, IL). The samples (4mm thickness, 5mm diameter) were prepared and polymerized for 20s with a light emitted diode unit. After fabrication, each sample was immediately immersed in 75wt% ethanol/water solution used as extraction fluid and stored in the amber colored bottles at room temperature. Ethanol/water samples were taken (0.5mL) at predefined time intervals:10m (T1), 1h (T2), 24h (T3) and 30 days (T4). These samples were analyzed by HPLC. The obtained data were analyzed with one-way ANOVA and Tukey HSD at significance level of p<0.05. RESULTS Amount of eluted Bis-EMA and Bis-GMA from Tetric Evo Ceram Bulk Fill and amount of eluted TEGDMA and HEMA from X-tra Fill higher than others composites (p<0.05). SIGNIFICANCE Residual monomers were eluted from bulk fill composite resins in all time periods and the amount of eluted monomers was increased with time.

Kinetic and thermodynamic investigation of mancozeb degradation in tomato homogenate during thermal processing.

BACKGROUND The kinetic and thermodynamic parameters of mancozeb degradation in tomato homogenates under the conditions prevailing in the manufacture of tomato products (at 60-100 °C for 0-60 min) were investigated. A gas chromatography-mass spectrometry method was used to analyse residual mancozeb in tomato homogenate. Ethylenethiourea (ETU), the main toxic degradation product of mancozeb, was measured by high-performance liquid chromatography (HPLC)-with photodiode array detector (PDA). RESULTS The degradation of mancozeb and the formation of ETU in tomato homogenates were adequately described as first-order kinetics. Dependence of the rate constant followed the Arrhenius relationship. Apparent activation energies, temperature coefficients, half time and time to reduce to 90% of the initial value of mancozeb were calculated as kinetic parameters. The thermodynamic parameters of mancozeb were also described as Δg(d) = - 2.440 and 7.074 kJ mol⁻¹; Δh(d) = - 32.555 and - 42.767 kJ mol⁻¹; Δs(d) = - 0.090 and - 0.150 kJ mol⁻¹ K⁻¹; K(e) = 0.414 and 9.797 L g⁻¹ for 333 and 373 K respectively. CONCLUSION Current findings may shed light on the reduction of mancozeb residue and its toxic degradation product during thermal processing of tomatoes and may also be valuable in awareness and prevention of potential risks from dietary exposure.

Acrylamide Contents of Commonly Consumed Bread Types in Turkey

In this study, levels of acrylamide in different bread samples obtained from a Turkish market were investigated. Acrylamide contents of the samples were determined by a gas chromatography-mass spectrometry method. The samples (n = 43) were commonly consumed, different types of breads, including white wheat bread, stone oven wheat bread, wheat bran bread, rye bread, whole grain bread, and whole wheat bread. Results revealed that the acrylamide contents of the samples show a considerable variation among different types of breads as well as within the same type. Crumb-crust ratio of the samples was also considered during the experiments. The contents of acrylamide in breads ranged from below the limit of quantification to 695 μg kg−1 and the mean acrylamide content was 225 μg kg−1. The highest mean level of acrylamide was detected in whole wheat bread.

Ion Chromatographic Determination of Free Cyanide in Different Classes of Bottled Natural Mineral Water Consumed in Turkey

An ion chromatographic method for the quantitative determination of free cyanide in bottled natural mineral waters were measured in terms of selectivity, linearity, the limit of detection, limit of quantification, repeatability, precision, and accuracy. Chromatographic separation of free cyanide ions was accomplished with an anion-exchange column and detected by pulsed amperometric detection with a silver working electrode. The method was found to be selective, linear (r2 = 0.999) at a concentration range of 0.5 to 134 μg L−1, precise, and accurate. Recovery values of free cyanide in all classes of natural mineral water varied from 65.9 ± 1.6 to 95.2 ± 0.7 at different spiking levels (5–70 μg L−1). Parameters (total dissolved solids, mineral interferences, and added sodium hydroxide) affecting the recovery values were studied in this project. The limit of detection and limit of quantification were found to be 0.295 and 0.983 μg L−1, respectively. The proposed method was applied to 27 different brands of commercially available bottled natural mineral water products sold in Turkish markets. These natural mineral waters were classified as: (i) very low mineral concentration, (ii) low mineral concentration, (iii) intermediate mineral concentration, and (iv) high mineral concentration based on their total dissolved solids contents according to European Union Directive (Directive 80/777/EEC). Levels of free cyanide residues in the samples ranged from > limit of detection to 6.12 μg L−1. The highest average concentration of free cyanide residues was found in the class of “high mineral concentration waters.” However, the determined free cyanide values in all of the tested natural mineral water samples were found to be within the limits of European Union legislation.

Rapid and sensitive determination of the prochloraz residues in the cultivated mushroom, Agaricus bisporus (Lange) Imbach

The QuEChERS (quick, easy, cheap, efficient, rugged, and safe) sample preparation method and gas chromatography-electron capture detector (GC-ECD) were adopted for rapid extraction and determination of prochloraz residues in cultivated mushrooms. The results were further confirmed by using a gas chromatography-mass spectrometry (GC-MS) system. The method showed that there was a good linear relationship with a correlation coefficient of r2 = 0.999 in the concentration ranges from 52.9 to 1000 μg L−1. The limit of detection (LOD) of the GC-ECD method was 15.9 μg kg−1 and the limit of quantification (LOQ) was 52.9 μg kg−1. The data satisfactorily demonstrated the good repeatability of the method with relative standard deviations (RSDs) lower than 20%. The recovery values for spiked mushroom samples were 100.6 ± 1.6% and 105.6 ± 3.9% for 250 and 1000 μg kg−1, respectively. The samples from seven different mushroom growing facilities were analyzed. The residue levels of prochloraz ranged from <LOQ to 105.4 ± 16.9 μg kg−1. Although, this was the first study on determination of prochloraz residues in mushroom samples by GC-ECD after QuEChERS extraction, the adopted method adequately met the validation criteria and was successfully applied to analyze prochloraz residues in the mushroom samples. Therefore, this method could be regarded as a new alternative for routine analysis of trace levels of this most commonly used pesticide in mushroom production.

Reduction of pesticide residues from tomatoes by low intensity electrical current and ultrasound applications

In this study, effects of low intensity electrical current (EC) and ultrasound (US) treatments on the reduction of some important pesticides (captan, thiamethoxam and metalaxyl) residues in tomato samples were investigated. Three different currents (200, 800 and 1400mA) of EC were applied at various time intervals (2, 4, 6, 8 and 10min). Two kinds of US treatments including ultrasonic bath (UB) at 40kHz and ultrasonic probe (UP) at 24kHz were tested for the determination of US effectiveness. In addition, synergistic effects of US on EC treatments were evaluated. The most effective conditions for reduction of captan, thiamethoxam and metalaxyl residues were 1400mA+40kHz, 800mA+24kHz and 1400mA+24kHz, respectively. The residues of captan, thiamethoxam and metalaxyl were reduced in the order of 94.24%, 69.80% and 95.06% by using these combinations. EC and US strategies can be considered as effective treatments in industrial scale in order to remove the pesticide residues from vegetables.

Determination of major sodium iodide symporter (NIS) inhibitors in drinking waters using ion chromatography with conductivity detector

Goiter is an important health problem all over the world and iodine deficiency is its most common cause. Perchlorate, thiocyanate and nitrate (called as major NIS inhibitors) are known to competitively inhibit iodide uptake by the thyroid gland and thus, human exposure to major NIS inhibitors is a public health concern. In this study, an ion chromatographic method for the determination of most common NIS inhibitor ions in drinking waters was developed and validated. This is the first study where an analytical method is used for the determination of major NIS inhibitors in drinking water by an ion chromatography system in a single run. Chromatographic separations were achieved with an anion-exchange column and separated ions were identified by a conductivity detector. The method was found to be selective, linear, precise accurate and true for all of interested ions. The limits of the detections (LOD) were estimated at 0.003, 0.004 and 0.025mgL(-1) for perchlorate, thiocyanate and nitrate, respectively. Possible interference ions in drinking waters were examined for the best separation of NIS inhibitors. The excellent method validation data and proficiency test result (Z-score for nitrate: -0.1) of the FAPAS(®) suggested that the developed method could be applied for determination of NIS inhibitor residues in drinking waters. To evaluate the usefulness of the method, 75 drinking water samples from Antalya/Turkey were analyzed for NIS inhibitors. Perchlorate concentrations in the samples ranged from not detected (less than LOD) to 0.07±0.02mgL(-1) and the range of nitrate concentrations were found to be 3.60±0.01mgL(-1) and 47.42±0.40mgL(-1). No thiocyanate residues were detected in tested drinking water samples.

An eco-friendly, quick and cost-effective method for the quantification of acrylamide in cereal-based baby foods.

BACKGROUND The presence of acrylamide in cereal-based baby foods is a matter of great concern owing to its possible health effects. Derivatization followed by gas chromatography/mass spectrometry (GC/MS) is one of the most common methods to quantify acrylamide. However, it requires the use of toxic chemicals and is time-consuming. The aim of this study was to develop an eco-friendly, rapid and inexpensive method for the determination of acrylamide in cereal-based baby foods. RESULTS The method involves defatting with n-hexane, extraction into water, precipitation of proteins, bromination, extraction into ethyl acetate and injection into a GC/MS system. The effects of defatting, precipitation, treatment with triethylamine, addition of internal standard and column selection were reviewed. A flow chart for acrylamide analysis was prepared. To evaluate the applicability of the method, 62 different cereal-based baby foods were analyzed. The levels of acrylamide ranged from not detected (below the limit of detection) to 660 µg kg(-1). CONCLUSION The method is more eco-friendly and less expensive because it consumes very little solvent relative to other methods using bromine solutions and ethyl acetate. In addition, sample pre-treatment requires no solid phase extraction or concentration steps. The method is recommended for the determination of trace acrylamide in complex cereal-based baby food products.

Geographical origin of imported and domestic teas (Camellia sinensis) from Turkey as determined by stable isotope signatures

ABSTRACT In this study, stable isotope signatures (δ13C, δ15N, and δD) of both tea leaves and tea infusions were investigated to identify the geographical origin of Turkish domestic and imported tea samples. Sixteen domestic tea samples collected from different locations in the Black Sea Region, which produces almost 100% of tea in Turkey, and 11 imported tea samples (Kenya, India, Sri Lanka, Indonesia, and China) purchased from importers were studied. δ13C, δ15N, and δD in the samples were determined using isotope ratio mass spectrometry (IR-MS). δ13C in the samples ranged from −29.18 ± 0.01 to −25.7 ± 0.2, while δ15N ranged between 1.1 ± 0.2 and 5.2 ± 0.8. However, δD in the samples were found to be in the range from 56.5 ± 0.3 to 72 ± 1. The classifications of the tea samples into domestic and imported tea samples were achieved with 100% accuracy using multivariate statistical analyses (principal component analysis, PCA, and hierarchical cluster analysis, HCA). In conclusion, the domestic tea samples had a distinctive isotopic fingerprint and the isotopic ratios used in the study can be significant predictors in determination of the geographical source of Turkish tea.

Bazı Ticari Kraker, Bisküvi ve Bebek Bisküvilerindeki Akrilamid Miktarları

Bu calismada, Turkiye’de satilan 90 adet ticari kraker, biskuvi ve bebek biskuvisi orneklerindeki akrilamid duzeyleri brom turevlendirmesi sonrasinda Gaz Kromatografisi/Kutle Spektrometresi metoduyla arastirilmistir. Kraker ornekleri (n=30) tuzlu, peynirli, baharatli ve susamli krakerler olmak uzere 4 gruba ayrilmistir. Biskuvi ornekleri (n=27) ise 5 gruba ayrilarak sade, kakaolu, kepekli, tam bugday ve yulafli biskuviler olarak siniflandirilmistir. Bebek biskuvileri (n=33) markalarina gore gruplandirilmislardir. Kraker, biskuvi ve bebek biskuvisi orneklerindeki ortalama akrilamid duzeyleri sirasiyla 604, 495 ve 153 µg/kg olarak belirlenmistir. Akrilamid gidalarin kompozisyonuna ve isleme parametrelerine bagli olarak pek cok gidada bulunmakta ve duzeyleri farkli markalara ve gida cesitlerine gore degismektedir.