Miraç Ocak

Does caffeine bind to metal ions

Abstract The complex formation capacity of caffeine, a highly-consumed tea and coffee component, was determined for Ca, Mg, Fe, Zn, Pb, Mn, Co and Cr metal ions. The binding constants of metal ion–caffeine complexes for the metals chosen were determined spectrophotometrically. The results were compared with the known stability constants of metal ion–EDTA complexes, EDTA being known for its high metal binding capacity. Furthermore, iron chelating activity of caffeine, using the ferrozine reference method, was studied and compared with that of EDTA. The results showed very little complex formation capacity of caffeine with binding constants of 29.6, 22.4, 59, 396, 55, 9.3, 83 and 592 M −1 for Ca, Mg, Fe, Zn, Pb, Mn, Co and Cr metal ions, respectively, in contrast to that of EDTA. The iron chelating activity of caffeine was also found to be 6%, which was considered to be quite low compared with EDTA.

An excellent copper selective chemosensor based on calix[4]arene framework

The article depicts a detailed study regarding copper selective chemosensing and complexation nature of 5,11,17,23-tetrakis[(N,N-diphenylamino)methyl]-25,26,27,28-tetrahydroxycalix[4]arene (PAC4). Its photophysical characteristics in various solvents of different polarities along with the influence of acid and base on its spectral properties in these solvents are also discussed. The complexation affinity of PAC4 with regard to its latent applications as Cu(II) selective colorimetric and fluorescent sensor among the selected series of various cations such as Li(I), Na(I), K(I), Rb(I), Ba(II), Sr(II), Al(III), Fe(III), Cd(II), Co(II), Hg(II), Mn(II), Ni(II), Pb(II) and Zn(II) was examined by UV-visible and fluorescence emission spectroscopy in dichloromethane:acetonitrile (DCM:MeCN) solvent system. In addition, the process of complexation has been investigated through Jobs plot and it has been observed that the complex between PAC4 and Cu(II) is formed in 1:1 stoichiometric ratio. The complex formation between PAC4 and Cu(II) has also been confirmed by FT-IR spectroscopy and thermal gravimetric analysis (TGA).

Bifunctional calix[4]arene sensor for Pb(II) and Cr2O7(2-) ions.

A readily available chromionophore 5,11,17,23-tetra-tert-butyl-25,27-bis(hydrazidecarbonylmethoxy)-26,28-dihydroxycalix[4]arene (HCC4) was employed as a chromogenic sensing probe selective for Pb(II) and Cr2O72− ions among a series of various ions such as Li(I), Na(I), K(I), Rb(I), Ba(II), Sr(II), Al(III), Cd(II), Co(II), Cu(II), Hg(II), Ni(II), Pb(II) and Zn(II) as well as Cr2O72−, CH3CO2−, Br−, Cl−, F−, I−, ClO4− and NO3− that have been examined by UV-visible and fluorescence spectroscopic techniques. The HCC4 in DCM-MeCN system forms 2:1 (ligand-metal) complex with Pb(II). It also shows 2:1 stoichiometry with Cr2O72−. The complexation phenomenon has been confirmed by FTIR spectroscopy that favors the selective nature of HCC4 with Pb(II) and Cr2O72−. Thermal gravimetric analysis (TGA) also supports its utility in drastic conditions.

New calix[4]arene based highly selective fluorescent probe for Al3+ and I−

This approach highlights the synthesis of a 2-hydroxy naphthalene functionalized calix[4]arene based fluorophoric Schiff base, C4SB. The ion-binding property of the C4SB fluoroionophore is probed with a number of cations and anions and the recognition events were monitored by UV-visible and fluorescence spectral changes. C4SB based on a photoinduced electron transfer mechanism exhibits a selective “turn-on” response towards Al3+ and a “turn-off” response for I− in the presence of other competing ions with certain observable spectral changes. The selective behavior of the probe is visualized in the presence of competing ions. The interference study reveals that Hg2+ causes some disturbance to the C4SB and Al3+ interaction. C4SB forms a (1:1) stoichiometric complex with both Al3+ and I− and their binding constants are calculated as 2.49 × 105 and 9.24 × 103, respectively. Moreover, the complexes were characterized through FT-IR spectroscopy.

Cu2+ Selective Chromogenic Behavior of Calix[4]arene Derivative

This study involves the copper selective chromogenic response of 5, 11, 17, 23-Tetrakis (N-pyrrolidinomethyl)-25, 26, 27, 28-tetrahydroxycalix[4]arene based mannich base (3). Complexation ability of (3) was explored by examining the effect of a series of various metal ions, such as Li+, Na+, K+, Ag+, Ba2+, Ca2+, Mn2+, Mg2+, Sr2+, Ni2+, Cd2+, Co2+, Cu2+, Hg2+, Pb2+, Zn2+, Fe2+, Fe3+, and Al3+, by using UV-visible spectroscopy. Ligand (3) exhibited pronounced selectivity toward Cu2+ even in the presence of various co-existing ions. The stoichiometric analysis, i.e., Jobs plot revealed that (3) form 1:1 complex with Cu2+ ion in DMF-H2O system. The complexation phenomenon was confirmed by FT-IR spectroscopy that favors the selective nature of (3) with Cu2+.

Metal ion complexation in acetonitrile by cone, di-ionised calix[4]arene-1,2-crown ethers with two pendant dansyl fluorophores

Four cone calix[4]arene-1,2-crown ethers each with two ionisable side arms containing dansyl groups are synthesised. The crown ether ring on the lower rim is varied from crown-4 to crown-5 with hydrogen or tert-butyl groups on the para position of the upper rim. Di(tetramethylammonium) salts of the di-ionised ligands are utilised for spectrofluorimetric titration experiments in MeCN. The influence of alkali metal, alkaline earth metal and selected transition and heavy metal (Co2+, Fe2+, Hg2+, Mn2+, Pb2+, Zn2+ and Fe3+) cations on the spectroscopic properties of the two dansyl groups linked to the lower rim of the conformationally locked, di-ionised calix[4]arene-1,2-crown ether frameworks is investigated by emission spectrophotometry. All of the metal cations induce red shifts in the emission spectra of the di-ionised ligands. The metal cations produce enhancement or quenching of the fluorescence emissions. Changes in the fluorescence emission as a function of the metal cation identity, the lower rim crown ether ring size and the absence or presence of upper rim tert-butyl groups are investigated.

Calix[4]arene Based Dual Fluorescent Sensor for Al3+ and S2O72−

AbstractSpecific functionalized calix[4]arene based fluorescent chemosensor was synthesized for cations and anions binding efficiency examination. Receptor C4MA displayed strong affinity for Al3+and S2O72− with enhanced fluorescence intensity. The selective response of C4MA was investigated in the presence of different co-existing competing ions. The limit of detection (LOD) of Al3+and S2O72− was calculated as 2.8 × 10−6 M and 2.6 × 10−7 M respectively. Sensor C4MA forms (1:1) stoichiometric complex with both Al3+ and S2O72− and their binding constants were calculated as 12.1 × 104 and 8.3 × 103 respectively. Complexes were also characterized through FT-IR spectroscopy. Graphical Abstractᅟ

Simultaneous Determination of Sunset Yellow FCF, Allura Red AC, Quinoline Yellow WS, and Tartrazine in Food Samples by RP-HPLC

An efficient method was developed for the simultaneous determination of Sunset Yellow FCF (E110), Allura Red AC (E129), Quinoline Yellow WS (E104), and Tartrazine (E102) in food samples by RP-HPLC. The mentioned food dyes were analyzed at room temperature for 23 min with gradient elution. Three mobile phases were used for the elution, and mobile phase A was an acetate buffer (pH = 7.5, 1%), mobile phase B was acetonitrile, and mobile phase C was methanol. The flow rate was 1.0 mL min−1, and the injection volume was 20 µL. The linear ranges were 0.72–50 mg L−1, 0.24–50 mg L−1, 0.75–10 mg L−1, and 0.69–50 mg L−1 for Tartrazine, Quinoline Yellow WS, Sunset Yellow FCF, and Allura Red AC, respectively. R2 values were 0.999 for all dyes. Limits of detection were 0.24 mg L−1, 0.08 mg L−1, 0.25 mg L−1, and 0.23 mg L−1 for Tartrazine, Quinoline Yellow WS, Sunset Yellow FCF, and Allura Red AC, respectively. The relative standard deviation (RSD) of the measurements for all of the four dyes was between 0.56 and 1.65% intraday measurements. This method was successfully applied in the determination of the mentioned dyes in ice pops, gummy bears, chewing gum, and sweets candy samples.