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Öğe Application of central composite design for the optimization of on-line solid phase extraction of Cu-2 (+) by calix[4]arene bonded silica resin(ELSEVIER SCIENCE BV, 2015) Memon, Fakhar N.; Ayyilidiz, H. Filiz; Kara, Huseyin; Memon, Shahabuddin; Kenar, Adnan; Leghari, Muhammad Khan; Topkafa, MustafaPresent study deals with the optimization of on-line solid phase extraction of Cu2+ using calix[4]arene based silica resin by the assessment of central composite design of response surface methodology. The immobilized resin was characterized with FT-IR and SEM techniques. The data obtained from experimental program of central composite design was used to model the parameters that significantly affect on Cu2+ extraction. The variables chosen were metal ion concentration, pH, and temperature. Second-order quadratic model was used to approximate the effect of variables on extraction efficiency. Furthermore, suggested model was also validated with the analysis of variance. The predicted values were in good agreement with experimental results, suggesting proficient application of central composite design as an economical alternative to acquire maximum amount of information for the modeling of on-line solid phase extraction with little number of experiments. Additionally, data obtained for different concentrations was analyzed by Freundlich, Langmuir, D-R isotherms, and Scatchard plot analysis. The results suggested that Langmuir isotherm was best fit model with R-2 0.99, the energy calculated from D-R isotherm was 15.14 KJ/mol suggesting that chemical force is involved in sorption process. The method was also validated for its linearity, accuracy, and precision. (C) 2015 Elsevier B.V. All rights reserved.Öğe Copper sorption efficiency of p-tetranitrocalix[4]arene based high performance liquid chromatographic column(DESALINATION PUBL, 2016) Durmaz, Fatih; Memon, Fakhar N.; Memon, Shahabuddin; Memon, Ayaz A.; Memon, Naeem A.; Kara, HuseyinPresent study deals with the sorption characteristics of p-tetranitrocalix[4]arene (3) appended silica-based high-performance liquid chromatographic (HPLC) column utilized for preconcentration, determination, and purification of Cu2+ from water. The sorption characteristics of the HPLC column were investigated for Cu2+ in column agreement. The experiments were performed in five steps that were monitored using UV-visible diode-array detector. However, all the HPLC experimental results were reconfirmed by using atomic absorption spectrophotometer. The effect of concentration on the sorption efficiency of the column was evaluated for Cu2+ and data obtained was investigated using Langmuir and Freundlich sorption isotherms. The value of coefficient of determination (R-2), i.e. 0.99, suggested that the Freundlich sorption isotherm was found to be the best fit model for Cu2+. The developed method was validated for system efficiency, accuracy, and precision, while the data obtained revealed that the developed column could be applied for the sorption of Cu2+ with adequate efficiency and repeatability.Öğe New potential humic acid stationary phase toward drug components: Development of a chemometric-assisted RP-HPLC method for the determination of paracetamol and caffeine in tablet formulations(WILEY-V C H VERLAG GMBH, 2016) Topkafa, Mustafa; Ayyildiz, Hamide Filiz; Memon, Fakhar N.; Kara, HuseyinA new humic acid based stationary phase has been used, for the first time, to achieve the separation and quantification of paracetamol and caffeine in pharmaceutical preparations under reversed-phase high-performance liquid chromatography conditions. Central composite design was applied as a powerful tool to optimize the most dominant parameters that influence the resolution of reversed-phase high-performance liquid chromatography, that is, mobile phase composition (acetonitrile percentage in water), flow rate, and column temperature. The optimum conditions were obtained as 21.69%, 1.5 mL/min, and 15 degrees C, respectively, with the aid of a second-order quadratic model and desirability function. Under the optimum conditions, the peaks could be baseline separated within 10 min. For the developed reversed-phase high-performance liquid chromatography method, the linearity was investigated in the concentration ranges of 2-160 mg/mL (R-2 = 0.999) for paracetamol and 2-9.9 mg/mL (R-2 = 0.991) for caffeine. Mean recoveries for paracetamol and caffeine were 95.90 and 95.68%, respectively. The limits of detection and quantification were 4.1 x 10(-4) and 1.3 x 10(-3) mg/mL for paracetamol and 1.6 x 10(-4) and 5.0 x 10(-4) mg/mL for caffeine. The results showed that the new humic acid based stationary phase is very suitable for the separation of paracetamol and caffeine in pharmaceutical preparations and, thus it can be used effectively in the pharmaceutical industry.Öğe Preconcentration and Determination of Toxic Metals by A New Calix[4]arene Bonded HPLC Column(SPRINGER HEIDELBERG, 2013) Durmaz, Fatih; Memon, Fakhar N.; Memon, Naeem A.; Memon, Sibghatullah; Memon, Shahabuddin; Kara, HuseyinThe present study deals with the preconcentration and determination of toxic metal ions using p-tetranitrocalix[4]arene (3) appended silica-based new HPLC column. The synthesized material was characterized using Fourier transform infrared and scanning electron microscopy techniques. The sorption characteristics of the HPLC column were investigated for three toxic metals (Cd2+, Hg2+ and Pb2+) in column agreement. The experiments were performed in five steps that were monitored using a UV-visible diode-array detector. However, all the HPLC experimental results were reconfirmed by using atomic absorption spectrophotometer. The effect of concentration on the sorption efficiency of the column was evaluated for all the three metals and the data obtained were investigated using Langmuir, Freundlich and Dubinin-Redushkevich (D-R) sorption isotherms. The value of coefficient of determination (R (2)), i.e. 0.99, suggested that the Freundlich sorption isotherm was found to be the best-fit model for all the three toxic metal ions, whereas, mean free energy was calculated from the D-R isotherm as 5.3, 5.7, and 5.8 kJ/mol for Pb2+, Cd2+, and Hg2+, respectively; suggesting that physical electrostatic force is involved in the sorption process. The developed method was validated for system efficiency, accuracy, and precision.Öğe Removal of ciprofloxacin from aqueous solution using wheat bran as adsorbent(TAYLOR & FRANCIS INC, 2019) Khokhar, Tahira Sarwar.; Memon, Fakhar N.; Memon, Ayaz Ali.; Durmaz, Fatih.; Memon, Shahabuddin.; Panhwar, Qadeer Khan.; Muneer, Saba.Current study describes sorption of antibiotic drug (ciprofloxacin) by using nontoxic and biocompatible carrier, i.e., wheat bran (WB). For sorption study, various parameters were optimized and Freundlich, Dubinin-Radushkevich, Langmuir, and Temkin isotherm models were applied to demonstrate the mechanism of sorption, while kinetics study for sorption was evaluated using diffusion models, pseudo-first-order kinetic (Langergren) and pseudo-second-order (Ho and McKay) kinetic models. In addition, thermodynamics study was also carried out. However, sorption of ciprofloxacin was pH depended and it showed 75% drug release in alkaline medium (at pH = 1.5) indicating the good release ability of WB for ciprofloxacin.Öğe Selective online solid-phase extraction of copper using p-morpholino-methylcalix[4]arene appended silica-based column(TAYLOR & FRANCIS INC, 2019) Memon, Naeem A.; Memon, Fakhar N.; Kara, Hatice K.; Kara, Hüseyin.; Sherazi, Sayed T. H.; Memon, Ayaz A.; Memon, Shahabuddin.; Leghari, Muhammad K.This study deals with investigation of selectivity of p-morpholino-methylcalix[4]arene appended silica from a group of metal ions having similar charge and radii. The values of distribution ratio revealed that modified silica possess higher selectivity for Cu2+. In addition, relative selectivity coefficients of modified silica were found to be 24.1, 13.8, 8.6 and 4.01 for Cu2+/Ni2+, Cu2+/Co2+, Cu2+/Cd2+, Cu2+/Pb2+, respectively. The maximum adsorption capacity was 1.5 mmolg(-1). The reusability data suggested no any loss of adsorption capacity of this material up to 10 cycles. The developed material was also applied for determination of copper in lake water samples with satisfactory results.Öğe Simultaneous determination of some basic dyes using p-tetranitrocalix[4]arene-appended silica-based HPLC column(ROYAL SOC CHEMISTRY, 2014) Memon, Shahabuddin; Memon, Fakhar N.; Durmaz, Fatih; Memon, Naeem A.; Memon, Ayaz A.; Kara, HuseyinThis study focuses on the synthesis, characterization and application of p-tetranitrocalix[4]arene-appended silica-based material as a stationary phase in high-performance liquid chromatography for the simultaneous separation of some basic dyes such as methyl violet, methyl green and methylene blue. The effect of the pH of mobile phase on the retention, separation and selectivity of these compounds was investigated. The method was validated for system efficiency, linearity, accuracy, precision, limit of detection and quantification. The limits of detection were 0.1, 0.5 and 0.3 mg L-1; whereas, the limits of quantification were observed to be 1, 1.2 and 0.9 mg L-1 for methyl violet, methyl green and methylene blue, respectively. The separation efficiency of the p-tetranitrocalix[4]arene-appended silica-based column was also compared to that of the octadecylsilane column.Öğe Synthesis and antimicrobial assessment of Fe3+ inclusion complex of p-tert-Butylcalix[4]arene diamide derivative(HINDAWI LTD, 2019) Chandio, Anwar Ali.; Memon, Ayaz Ali.; Memon, Shahabuddin.; Memon, Fakhar N.; Panhwar, Qadeer Khan.; Durmaz, Fatih.; Nizamani, Shafi Muhammad.; Brohi, Nazir Ahmed.Present study deals with the synthesis of the p-tert-butylcalix[4]arene diamide derivative as ligand (L) and its Fe3+ complex, followed by its characterization using TLC and FT-IR, while UV-Vis and Job's plot study were performed for complex formation. Antimicrobial activity of the derivative (L) and its metal complex was carried out by the disc diffusion method against bacteria (Escherichia coli and Staphylococcus albus) and fungi (R. stolonifer). Different concentrations of the derivative (L) (6, 3, 1.5, 0.75, and 0.37 mu g/mL) and its Fe3+ complex were prepared, and Mueller-Hinton agar was used as the medium for the growth of microorganisms. Six successive dilutions of the derivative (L) and Fe3+ complex were used against microorganisms. Two successive dilutions (6 and 3 mu g/mL) of the derivative (L) showed antibacterial action against both Gram-positive and Gram-negative bacteria. In addition, three successive dilutions (6, 3, and 1.5 mu g/mL) of the derivative (L) showed antifungal activity. However, all of six dilutions of the Fe3+ complex showed antimicrobial activity. Derivative (L) showed 3 and 1.5g/mL minimum inhibitory concentrations (MIC) against bacteria and fungi, respectively. On the contrary, its Fe3+ complex showed 0.37g/mL value of MIC against bacteria and fungi. Hence, Fe3+ complex of the derivative (L) was found to be a more effective antimicrobial agent against selected bacteria and fungi than the diamide derivative (L).
