Melek Merdivan

Reduction of Ochratoxin A Levels in Red Wine by Bentonite, Modified Bentonites, and Chitosan

Adsorption method may play an important role to remove ochratoxin A (OTA) from wine by bentonite (B), nonylammonium bentonite (NB), dodecylammonium bentonite (DB), KSF-montmorillonite (KSF), and chitosan bead (CB). The optimum conditions of OTA adsorption from synthetic solutions were revealed at room temperature and pH 3.5. The adsorption equilibria of B and NB were almost established within 120 and 240 min, respectively. DB, KSF, and CB had about 90 min of equilibration time. The adsorption efficiency carried out in the synthetic OTA solution did not change remarkably when the amounts of adsorbents were 25 mg for bentonite, DB, and KSF and 100 mg for NB and CB. Furthermore, 25 mg of adsorbents was used at all adsorption studies in synthetic solution. The adsorption isotherm was fitted with mostly a Freundlich equation with respect to the correlation coefficients. The adsorption data were evaluated using Langmuir and Freundlich equations having Kf values ranging from 0.011 to 9.5 with respect to correlation coefficients (R2 = 0.900-0.977). DB and KSF have the highest adsorption capacity for OTA in synthetic solutions. In wine, the removal of OTA was succeeded at a percentage of 60-100 by KSF and CB. Furthermore, the highest adsorption capacity of OTA for red wine was obtained by using 250 mg of KSF, which caused less damage to the nature of wine and also low adsorption of polyphenols and anthcyans.

Polymer Supported Humic Acid for Separation and Preconcentration of Thorium(IV)

Abstract The resin impregnating humic acid (HA) onto XAD‐4 has been prepared to investigate adsorption behaviour of Th(IV). The characterization of the resulting resin has been carried out by infrared spectral data and sorption capacity. Maximum adsorption capacity of Th(IV) on the resin is found to be 1.51 × 10−4 mol g−1 at pH 4. The sorbent was found to possess a high selectivity for Th(IV) with an optimum extraction pH around 3–7. Recoveries for Th(IV) determined prior to breakthrough were found to be quantitative (96–99%). The resin exhibits good chemical stability, reuseability, and a faster rate of equilibration for Th(IV) determination. The influence of several ions as interferents is discussed. The method has been successfully applied for the separation of Th(IV) in synthetic mixtures.

Solid‐Phase Extraction of Silver in Geological Samples and its Determination by FAAS

Abstract A macroporous and a nonionic resin, Amberlite XAD‐16 as a solid sorbent and N,N‐diethyl‐N′‐benzoylthiourea (DEBT) as a chelating agent have been used for the selective separation and preconcentration of silver. Sorption of silver was studied in three ways: sorption on DEBT impregnated Amberlite XAD‐16 by batch and column processes and sorption of Ag‐DEBT complex on Amberlite XAD‐16 by column process. Factors affecting the sorption and desorption of silver ion were investigated. The stripping of silver was achieved by using either sodium thiourea or sodium thiosulfate solution. The silver ion capacity of impregnated resin was found to be 11.22 mg Ag+/g resin and 870 µg Ag+/g resin for batch and column processes, respectively. It was 370 µg Ag+/g resin for Ag‐DEBT complex. The interference effects of possible co‐existing metal ions and some electrolytes were investigated. The applicability of the proposed method was shown by analyzing the geological copper ore samples.

Solid phase extractive preconcentration of silver from aqueous samples

N,N-dibutyl-N1-benzoylthiourea (DBBT) impregnated onto a polymeric matrix, Amberlite XAD-16 was prepared. The separation and enrichment of Ag(I) from solution was investigated. Effective extraction conditions were optimized in column methods prior to determination by atomic absorption spectrometry. The optimum pH range for quantitative adsorption is 2–5. Quantitative recovery of Ag was achieved by stripping with 1mol L−1 thiourea in 1mol L−1 HCl. The sorption capacity of resin is 0.115mmol Ag+ g−1 resin. The relative standard deviation and detection limit was 3.1% for 1µg Ag+ mL−1 solution and 0.11µg L−1, respectively. The method was used for the determination of silver in geological water samples.

Development of new dispersive liquid–liquid microextraction technique for the identification of zearalenone in beer

A method has been developed for the quantification of zearalenone (ZEN) in beer, using dispersive liquid–liquid microextraction (DLLME) followed by high performance liquid chromatography (HPLC). The optimisation of the method was performed using both high performance thin layer chromatography using a TLC-scanner and HPLC. Chloroform was used as the extraction solvent, and acetonitrile as the dispersive solvent. Under the optimum conditions, the enrichment factor for ZEN was 43.3 and the extraction recovery was 83%. Validation was performed for a working range of 0.4–120 pg μL−1 ZEN. The limit of detection was 0.12 pg μL−1. The recoveries of the method for ZEN from beer samples at 10 and 20 pg μL−1 spiking levels were 71–108%. Different brewing styles of thirteen commercial beer samples were analysed, and ZEN was detected in 11 beer samples.

Formation And Characterization Of Humic Acids From Low Rank Anatolian Coals By Air Oxidation

Abstract The results of this study are aimed at evaluating the effects of air oxidation time, temperature and demineralization on humic acid production from two low-rank Anatolian coals. Two Anatolian low rank coals were studied at 120 and 200°C up to 10 days with and without demineralization. The best results for humic acid formation were obtained at a high temperature for longer times. Demineralization effect is negligible for studied coals. The rate of humic acid formation increased at first with increase in oxidation time, reached a maximum, and then decreased at high oxidation time. Also, a detailed study of the elemental composition, the characterization by FTIR, and the acidity of humic acids are reported.

Effect of Molten Caustic Leaching on Demineralization and Desulfurization of Asphaltite

Abstract Molten caustic leaching process is effective in reducing significant amounts of ash-forming minerals, pyritic sulfur, and organic sulfur from solid fossil fuels. The effect of leaching asphaltite samples from Seguruk and Harbul collieries of Sirnak and Silopi asphaltite fields (situated in the Southeast Anatolia region of Turkey) with molten sodium hydroxide and followed by mild acid on demineralization and desulfurization was investigated. The effects of alkali/asphaltite ratio, time, and temperature on the leaching efficiency were detailed, and the experimental results are presented here. Chemical demineralization and desulfurization of asphaltite samples using molten sodium hydroxide were investigated in the temperature range of 200°C–400°C. The percentage of demineralization and desulfurization increased with the increase in alkali/asphaltite ratio. The removal of total sulfur and ash increased with increasing leaching temperature and time. Most of the inorganic sulfur and a significant portion of the organic sulfur were removed.

Absorption and fluorescence properties of aryl substituted porphyrins in different media.

Absorption and fluorescence properties of aryl substituted porphyrins, 5,10,15,20-tetra-4-oxy(aceticacid)phenylporphyrin (TAPP), 5,10,15,20-tetra-(4-phenoxyphenyl) porphyrin (TPPP), 5,10,15,20-tetra-(3-bromo-4-hydroxyphenyl) porphyrin (TBHPP), and 5,10,15,20-tetra-p-chloromethylphenyl porphyrin (CMPP) were investigated. The UV/vis absorption, fluorescence and excited spectra as the fluorescence quantum yields and fluorescence lifetimes for the compounds were measured in organic solvents (chloroform (CHCl(3)), tetrahydrofuran (THF)) and immobilized media (PVC film, sol-gel matrix). The fluorescence quantum yields of TAPP and TPPP were higher than the others. The fluorescence lifetimes of all studied porphyrin derivates were found to be fifty percent lower and their fluorescence intensities were increased fifty percent more in both of immobilized mediums, as compared to organic solvents.

The Effect of Degree of Impregnation in Amberlite Resins with Organophosphorous Extractants for Y(III), La(III), Ce(III), Th(IV) and U(VI) Ions

Abstract Background: The sorption of Y(III), La(III), Ce(III), U(VI) and Th(IV) ions with solvent impregnated resins using diphenylphosphate (DPP), and diphenylphosphinic acid (DPPA) as extractant and Amberlite XAD 16 and Amberlite XAD 2000 as a polymeric support has been studied. The impregnated resins containing various amounts of extractants (10/90, 20/80, 50/50, 60/40) have been prepared by a dry method. The effects of pH, types of extractant, extractant content, surface area of polymeric support and contact time have been investigated by batch method. Results: The impregnation for DPP on XAD‐16 and XAD‐2000 was 111 and 46% at 60/40 extractant/resin mass ratio, respectively. The impregnation of DPPA at all ratios on both resins was found constant and lower than DPP. The sorption percentage of studied metal ions was within 90‐99% for DPP and DPPA on both resins after 20/80 extractant/resin mass ratio. Conclusions: The sorption of DPP on Amberlite XAD 16 and XAD 2000 resins is rather more than DPPA. It could be seen that 20/80 extractant/resin mass ratio is generally adequate for single metal analysis where 60/40 could be suitable for multi‐metal analysis.

Determination of platinum, palladium and rhodium in Pt-catalysts by high performance thin layer chromatography using densitometry

The determination of palladium and platinum in alumina-supported bimetallic Pt-Re, Pd and Pt catalysts at the 0.03 and 0.3% (m/m) levels, respectively, and of rhodium and platinum in platinum sieve catalysts at the 0.04% (m/m) level and in the 4.75–19.75% (m/m) range, respectively, is described. The platinum group metals in fresh or spent catalysts are determined chromatographically using densitometry by forming theirN,N-diethyl-N′-benzoylthiourea complexes. The precision of the method, %RSD, is 0.4–3.5, 2.2–6.7, and 4.2–6.0 for Pt, Pd and Rh, respectively. The accuracy was tested using alumina-based and active carbon platinum and palladium standards. The results were also compared with those obtained by FAAS. There was at most 8% difference between the results obtained with these methods, except for one active carbon based Pd standard.