Nalan Tüzmen

Mercury removal from synthetic solutions using poly(2-hydroxyethylmethacrylate) gel beads modified with poly(ethyleneimine)

In this study, the Hg2+ adsorption–desorption properties of poly(ethyleneimine) (PEI)-attached poly(2-hydroxyethylmethacrylate) (PHEMA) beads were investigated. Spherical PHEMA beads with an average size of 150–200 μm were obtained by suspension polymerization of 2-hydroxyethylmethacrylate conducted in an aqueous dispersion medium. Owing to the reasonably rough character of the bead surface, PHEMA beads had a specific surface area of 14.8 m2/g. PEI chains could be covalently attached onto the PHEMA beads with equilibrium binding capacities up to 50 mg PEI/g beads. PEI-attached PHEMA beads were utilized as adsorbent in the adsorption–desorption of Hg2+ ions from synthetic solutions. The adsorption process was fast; 90% of adsorption occurred within 45 min and equilibrium was reached at around 1 h. The maximum Hg2+ adsorption capacity obtained was 1.67 mmol/g at a pH of about pH 5.0. Adsorption behavior can be described at least approximately by the Langmuir equation. The metal-chelating beads can be easily regenerated by 0.1 M HNO3 with higher effectiveness. Adsorption of heavy metal ions from artificial wastewater was also studied. The adsorption capacities were 1.32 mmol/g for Hg2+, 0.34 mmol/g for Ni2+ and 0.42 mmol/g for Cu2+.

Selective cholesterol adsorption by molecular imprinted polymeric nanospheres and application to GIMS.

Molecular imprinted polymers (MIPs) are tailor-made materials with selective recognition to the target. The goals of this study were to prepare cholesterol imprinted polymeric nanospheres (CIPNs) and optimize their adsorption parameters and also to use CIPNs for adsorption of cholesterol (CHO), which is an important physiological biomacromolecule, from gastrointestinal mimicking solution (GIMS). Pre-polymerization complex was prepared using CHO as template and N-methacryloylamido-(l)-phenylalanine methyl ester (MAPA). This complex was polymerized with 2-hydroxyethyl methacrylate (HEMA). CHO was removed by MeOH and tetrahydrofuran (THF). Adsorption studies were performed after chacterization studies to interrogate the effects of time, initial concentration, temperature, and ionic strength on CHO adsorption onto CIPNs. Maximum adsorption capacity (714.17mg/g) was higher than that of cholesterol imprinted polymers in literature. Pseudo-second-order kinetics and Langmuir isotherm fitted best with the adsorption onto CIPNs. 86% of adsorbed cholesterol was desorbed with MeOH:HAc (80:20, v/v) and CIPNs were used in adsorption-desorption cycle for 5-times with a decrease as 12.28%. CHO analogues; estron, estradiol, testosterone, and progesterone were used for competitive adsorption. The relative selectivity coefficients of CINPs for cholesterol/estron and cholesterol/testosterone were 3.84 and 10.47 times greater than the one of non-imprinted polymeric nanospheres (NIPNs) in methanol, respectively.

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

Application of affinity microspheres for effective SPE cleanup before the determination of sulfamerazine by HPLC

This paper describes the application of poly (ethylene glycol dimethacrylate-N-methacryloyl-L-tryptophane methyl ester) [p(EGDMA-MATrp)] microspheres as an affinity sorbent for the SPE (solid phase extraction) cleanup of sulfamerazine (SMR) from food samples of animal origin before high performance liquid chromatography (HPLC) analysis. The microspheres were prepared by suspension polymerization of ethylene glycol dimethacrylate (EGDMA) and N-methacryloyl-L-tryptophane methyl ester (MATrp) as a crosslinker and a monomer, respectively. Various parameters affecting the SPE cleanup efficiency of the p(EGDMA-MATrp) microspheres (contact time, pH, initial SMR concentration, ionic strength etc.) were optimized. Under the optimized conditions, maximum adsorption capacity was found to be 8.55 ± 0.44 mg/g sorbent at pH 5.0. 90% of the adsorbed SMR was desorbed by using ACN:MeOH (5:5) mixture as a desorption agent. Applicability of the microspheres for the SPE cleanup of SMR residues in the food samples such as egg and milk with HPLC was also determined. It was demonstrated that the prepared p(EGDMA-MATrp) microspheres could be repeatedly applied for SPE cleanup of sulfamerazine before chromatographic analysis. Also, the recoveries of SMR in milk and egg samples were reasonably satisfactory and in the range of 71 to 90%.

Oxime-functionalized cryogel disks for catalase immobilization

Catalase is a protective enzyme against oxidative stress and converts hydrogen peroxide into water and molecular oxygen. In the current study, catalase immobilization was applied onto the oxime-functionalized cryogel disks. Cryogel disks were produced by free radical polymerization. After cutting as circular disks, oxime ligand (4-biphenylchloroglyoxime, BPCGO) was attached and oxime-functionalized cryogel disks were obtained. After optimization of several immobilization parameters such as pH, initial catalase concentration, temperature and ionic strength, maximum catalase load was detected as 261.7 ± 11.2mg/g for cryogel disk at pH5.0. Activity studies indicated that immobilization enhanced the enzyme activity in basic pH region, the temperature range of 15-35°C and at ionic strengths between 0.2 and 1.0M NaCl. Km was detected as 9.9 and 11.0mM and Vmax was 357.1 and 769.2μmol min-1 for free and immobilized catalase, respectively. kcat and Km/kcat values showed that immobilization enhanced the catalytic efficiency. Storage stability experiments demonstrated that immobilization increased the usability period. Furthermore, catalase desorption was achieved by 1.0M NaSCN at pH8.0 successfully and catalase adsorption capacity of oxime-functionalized cryogel disk was decreased by 9.9% at the end of 5 adsorption-desorption cycle.