Serap Seyhan Bozkurt

Separation and preconcentration of Pb(II) using ionic liquid-modified silica and its determination by flame atomic absorption spectrometry

A new method based on microcolumn packed with ionic liquid-modified silica combined with flame atomic absorption spectrometry has been developed for the determination of lead in environmental samples. Several factors influencing the preconcentration efficiency of lead and its subsequent determination, such as pH of the sample, flow rate, mass of ionic liquid, and interfering effect, have been investigated. Lead could be quantitatively retained by ionic liquid-modified silica in the pH range of 5-7, and then eluted completely with 3.0 mL 1.0 mol L(-1) HCl. The detection limit of this method for lead was 0.7 μg L(-1) with preconcentration factor of 185, and the relative standard deviation (RSD) was 4.2% at 0.1 μg mL(-1) Pb(II). This method has been applied for the determination of trace amount of lead in NIST standard reference material 2709 (San Joaquin Soil) and river water samples with satisfactory results.

Fluorescence-based sensor for Pb(II) using tetra-(3-bromo-4-hydroxyphenyl)porphyrin in liquid and immobilized medium

A new optical sensor for sensing of Pb(2+) in immobilized medium (PVC film) and ethanol medium was developed by using 5,10,15,20-tetra-(3-bromo-4-hydroxyphenyl)porphyrin (TBHPP) synthesized. The sensor-based TBHPP showed a linear response towards Pb(2+) in concentration range from 5x10(-6) to 4x10(-4)molL(-1) in PVC film and 5x10(-6) to 3x10(-4)molL(-1) in ethanol medium, with a working pH 7. The detection limit was 2x10(-8) and 4x10(-8)molL(-1) for Pb(2+) in PVC film and ethanol medium respectively. The response time of Pb(2+) was found as 4min for PVC film and 2min for ethanol medium. The sensor developed in two different mediums was used for lead determination in standard soil sample with satisfactory results.

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.

Can Hg(II) be Determined via Quenching of the Emission of Green Fluorescent Protein from Anemonia sulcata var. smaragdina

Anemonia sulcata var. smaragdina is a widely distributed Cnidarian species along Turkish coastlines. It is also a well-known example of a facultative symbiotic life form in sea ecosystems. Green fluorescent proteins (GFPs) in Anemonia sulcata var. smaragdina have vital roles in this symbiotic form. The fluorescence quenching by Hg(II) in the supernatants obtained from A. sulcata var. smaragdina was shown in this study. According to results, there was a statistical significant relationship (R2 = 0.9913) between increased Hg(II) concentration and decreased fluorescence intensity of GFP supernatants obtained from A. sulcata var. smaragdina. Mn(II), Fe(II), and Al(II) showed no interference effect and did not change the fluorescence intensity of GFP supernatants obtained from A. sulcata var. smaragdina. In conclusion, the fluorescence quenching of GFPs by Hg(II) can be a novel method to determine the Hg(II) levels in aqueous solution. Therefore, further researches are strongly warranted because of the possible potential applications of the fluorescence quenching of GFPs by Hg(II).

Use of ionic liquid based chitosan as sorbent for preconcentration of fluoroquinolones in milk, egg, fish, bovine, and chicken meat samples by solid phase extraction prior to HPLC determination

ABSTRACT The possibility of using ionic liquid based chitosan sorbent for the separation and preconcentration of fluoroquinolone antibiotics (marbofloxacin, enoxacin, ofloxacin, ciprofloxacin, and enrofloxacin) has been studied. For this reason, different ionic liquids were prepared and coated on the chitosan sorbent. The conditions of the preconcentration of fluoroquinolones on a microcolumn have been optimized and the extraction efficiencies of the prepared sorbents have been compared. The compounds were eluted with 5 mL of 20% NH3 (v/v, MeOH) solution and determined by HPLC with diode array and fluorescence detector. The limits of detection were found as 4.23 µ g L−1 for marbofloxacin, and 1.09 µg L−1 for enoxacin; 3.23 × 10−3 µg L−1 for ofloxacin; 8.39 × 10−3 µg L−1 for ciprofloxacin; and 19.50 × 10−3 µg L−1 for enrofloxacin. The developed method was applied for the analysis of fluoroquinolone in milk, egg, fish, bovine, and chicken samples and the recoveries were obtained in the range 70–100%. GRAPHICAL ABSTRACT

Ionic Liquid Based Dispersive Liquid–Liquid Microextraction for Preconcentration of Zearalenone and Its Determination in Beer and Cereal Samples by High-Performance Liquid Chromatography with Fluorescence Detection

A simple, fast, and efficient ionic liquid based dispersive liquid–liquid microextraction has been developed for the determination of trace amounts of zearalenone for the first time. Preconcentrated zearalenone was determined by high performance liquid chromatography with fluorescence detector. Two ionic liquids, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide and 1-methyl-3-octylimidazolium bis(trifluoromethanesulfonyl) imide were used as extraction solvents. Several analytical parameters affecting the extraction efficiency such as sample pH, type, and volume of dispersive solvent, volume of ionic liquid, time of extraction, and centrifugation were optimized. The 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide showed the better extraction efficiency. Thus, the method validation and the application of the method to real samples were carried out with 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide. Under the optimum conditions, the calibration curve for zearalenone determination was linear in the range of 1–750 µg L−1(R2 = 0.9960) and the limit of detection was 0.25 µg L−1 for zearalenone. The inter-day and intra-day precisions of the developed method were in the range of 1.36–3.02%. The method was successfully applied to beer and cereal (wheat and corn) samples. The recovery percentages of zearalenone for spiked samples were between were 80.0 and 100.0%.

DETERMINATION OF TRACE METAL IONS USING PORPHYRINS AS CHELATING AGENTS BY HIGH PERFORMANCE THIN LAYER CHROMATOGRAPHY-DENSITOMETRY

A method was developed for separation and quantitative determination of mercury, copper, cobalt, and zinc as porphyrin complexes using newly synthesized tetra-(3-bromo-4-hydroxyphenyl) porphyrin (TBHPP), tetra-(4-phenoxyphenyl) porphyrin (TPPP) and tetra-p-chloromethylphenyl porphyrin (CMPP) in aqueous medium by HPTLC densitometry. The method involves enrichment of metal ions as metal complexes with octadecyl cartridges and elution using tetrahydrofuran. The analysis was performed on HPTLC silica gel plates with acetone-chloroform (2:8, v/v) as the mobile phase for TBHPP and TPPP quantification and dichloromethane-chloroform-hexane (1:1:3, v/v) for CMPP quantification. Quality parameters were confirmed and detection limits were ranged from 0.16 to 0.92 ng μL−1. Detection was performed densitometrically in absorption-reflection mode around 420 nm. The method was found to be simple, precise and accurate for the determination of these metal ions in water and food sample.

Densitometric HPTLC analysis of the 5-hydroxymethylfurfural content of Turkish fruit wines and vinegars

A thin-layer chromatographic method with densitometric UV detection at 286 nm after ethyl acetate extraction is described for analysis of 5-hydroxymethylfurfural (HMF) in fruit wines and vinegars produced in Turkey. The retention factor, hRF, was 38 on silica gel HPTLC plates as stationary phase after development with toluene—ethyl acetate—90% formic acid 6:3:1 (v/v) as mobile phase. Recovery from samples spiked with different amounts HMF (2.0 and 5.0 ng μL−1) was usually in the range 95–112%. The limits of detection and quantification of the method were 0.045 and 0.125 ng mL−1, respectively. For robustness, within and between-day repeatability of the method were calculated as 4.5 and 8.6%, respectively. Seven types of Turkish fruit wines and three kind of Turkish vinegar tested were found to contain HMF in the ranges 0.5 to 13.2 ng μL−1 and 1.0 to 33.1 ng μL−1, respectively.

Separation and preconcentration of palladium using benzoylthiourea immobilized on a cationic surfactant coated silica gel

A method for separation and preconcentration of trace levels of palladium on silica-cetyltrimethyl ammonium bromide coated with N,N-diphenyl-N′-(4-bromobenzoyl)thiourea was reported. The effects of parameters such as pH, amount of silica, amount of ligand, flow rate, type and concentration of the stripping agent were investigated. Sorbed ions were quantitatively eluted using 4 mL of 0.2 mol L−1 thiourea. The preconcentration factors of 31.3 to 313 are easily achievable. The relative standard deviation of the method was <±5.85% for 10 replicate determinations of 0.002 to 1.0 μg mL−1 and the detection limit was 0.3 μg L−1. The applicability of the developed admicelle sorbent was investigated using synthetic samples and real samples such as standard reference material 2709 (San Joaquin Soil) and 2711 (Montana Soil).

Molecularly imprinted polymer based on magnetic ionic liquid for solid-phase extraction of phenolic acids

ABSTRACT In this study, 1-allyl-3-octylimidazolium tetrachloroferrate ionic liquid was first synthesized. Molecularly imprinted polymer was prepared by suspension polymerization using 1-allyl-3-octylimidazolium tetrachloroferrate as functional monomer and chlorogenic acid as template molecule. The polymer was characterized by Fourier transformed infrared spectroscopy and scanning electron microscopy. Thermal stability of the polymer was investigated. The solid-phase extraction method based on magnetic molecularly imprinted polymer was developed for gallic acid, protocatechuic acid, caffeic acid, chlorogenic acid, p-coumaric acid, and ferulic acid. The sample pH, the type and volume of stripping solution, sorbent amount, and extraction time were optimized for phenolic acids. The analysis of phenolic acids after extraction was carried out using high-performance liquid chromatography with UV detection. Limit of detection, limit of quantification, linear range, correlation coefficient, and reproducibilities of within-day and between-day for phenolic acids were determined. The residues of phenolic acids in apple samples were successfully detected by the developed method. Recovery of standard spiked apple samples was ≥81 for all the phenolic acids. GRAPHICAL ABSTRACT