Fluoride detection with a colorimetric and fluorescent dual-mode chemosensor

We designed a colorimetric and fluorescent dual-mode chemosensor ADM ((E)-2-(((2-amino-4,5-dichlorophenyl)imino)methyl)-6-methoxyphenol) for detecting fluoride (F⁻). The sensor ADM can detect F⁻ by colour and fluorescence changes. The colour change is from colourless to yellow, and the fluorescence change is a yellow turn-on. With the results of Job plot and electrospray ionisation mass spectrometry, the reaction of F⁻ and ADM turned out to be a 1:1 binding. The detection limits for F⁻ of ADM were 5.00 μM in ultraviolet–visible and 4.16 μM in fluorescence. The detecting process of F⁻ by ADM was demonstrated by ultraviolet–visible and fluorescent titrations, electrospray ionisation mass spectrometry, proton nuclear magnetic resonance titration and theoretical calculations.     

A selective sulphur‐containing colorimetric chemosensor for Cu2+

A highly selective sulphur‐containing colorimetric chemosensor APTS ((E)‐2‐(tert‐butyl)‐6‐(((2‐(phenylthio)phenyl)imino)methyl)phenol) was synthesised for detecting Cu²⁺. APTS showed a clear colour change from colourless to yellow with Cu²⁺. The detection limit of APTS for Cu²⁺ was 0.52 μmol/L. APTS could also be used as a test strip for detecting Cu²⁺. To understand the binding mode of APTS with Cu²⁺, ultraviolet‐visible spectroscopy and electrospray ionisation‐mass spectrometry analyses were conducted. The sensing mechanism of sensor APTS towards Cu²⁺ was proposed to be the combination of intramolecular charge transfer and ligand‐to‐metal charge‐transfer through theoretical calculations.     

A colorimetric Schiff base chemosensor for CN− by naked-eye in aqueous solution

A highly selective colorimetric chemosensor 6,6′-((1E,1′E)-hydrazine-1,2-diylidenebis(methanylylidene))bis(2,4-dichlorophenol) (1) based on the combination of hydrazine and 3,5-dichloro-2-hydroxybenzaldehyde was designed and synthesized. Receptor 1 showed exclusive response toward cyanide by a color change from colorless to yellow in aqueous solution. The binding mode of 1-CN⁻ species was determined to be a 1:1 stoichiometry through Job plot, ¹H NMR titration, and ESI-mass spectrometry analysis. Also, the sensor 1 could be recyclable simply through treatment with a proper reagent such as hydrochloric acid.     

Cu(II) selective sensor based on 5,7,12,14-tetramethyldibenzo[b,i]-1,4,8,11-tetraazacyclotetradecane in PVC matrix

5,7,12,14-tetramethyldibenzo[b,i]-1,4,8,11-tetraazacyclotetradecane, Me₄Bzo₂[14]aneN₄. (I) was synthesized and used as an electroactive material for the fabrication of membrane electrode in PVC matrix for the determination of Cu²⁺. The best performance was given by the membranes of macrocycle (I) with composition 5:3:100:150 (I:NaTPB:DBBP:PVC). The sensor worked well over a concentration range 2.5 × 10^–5–1.0 × 10^–1 M of Cu²⁺ with a slope of 30.2 ± 0.3 mV (decade)^–1 of Cu²⁺ activity, a fast response time of 13 ± 2 s and a lifetime of five months. The working pH range of this sensor is 2.6–5.5 and it shows excellent selectivity for Cu²⁺ over other mono-, di- and trivalent cations. Its performance in partially nonaqueous medium was found to be satisfactory. The sensor can also be used as an indicator electrode in the potentiometric titration of Cu²⁺ against EDTA and its determination in real samples.     

Quantification of the Molecular Species of TAG and DAG in Lesquerella (Physaria fendleri) Oil by HPLC and MS

Ten diacylglycerols (DAG) and 74 triacylglycerols (TAG) in the seed oil of Physaria fendleri were recently identified by high‐performance liquid chromatography (HPLC) and mass spectrometry (MS). These acylglycerols (AG) were quantified by HPLC with evaporative light scattering detector and electrospray ionization mass spectrometry of the lithium adducts of the AG in the HPLC fractions of lesquerella oil. The MS¹ ion signal intensities of molecular ions [M + Li]⁺ in HPLC fractions of an HPLC peak were used to estimate the ratios of AG in the HPLC peak. The ratios of TAG with the same mass in HPLC fractions were estimated by the ratios of the sums of MS² ion signal intensities from the neutral loss of the three fatty acids [M + Li ? FA]⁺. The ratio of DAG with the same mass were estimated by the ratio of the sums of two MS² ion signal intensities [M + Li ? FA]⁺ and [FA + Li]⁺ from the two different FA of a DAG. We have estimated the contents of ten molecular species of DAG and 74 molecular species of TAG in P. fendleri oil using this new method. The content of ten DAG combined was about 1 % and 74 TAG was about 98 %. The contents of DAG in decreasing order were: LsLs (0.25 %), LsLn (0.25 %), LsO (0.24 %), and LsL (0.11 %); and the contents of TAG in decreasing order were: LsLsO (31.3 %), LsLsLn (24.9 %), LsLsL (15.8 %), LsL‐OH20:2 (4.3 %), LsO‐OH20:2 (2.8 %), and LsLn‐OH20:2 (2.5 %).     

Synthesis and adsorption properties,toward some heavy metal ions,of a new polystyrene‐based terpyridine polymer

A novel polymeric ligand having 2,2′:6′,2″‐terpyridine as pendant group was prepared through a Williamson type etherification approach for the reaction between 4′‐hydroxy‐2,2′: 6′,2″‐terpyridine and the commercially available 4‐chloromethyl polystyrene. The chelating properties of the new polymer toward the divalent metal ions (Cu²⁺, Zn²⁺, Ni²⁺, and Pb²⁺) in aqueous solutions was studied by a batch equilibration technique as a function of contact time, pH, mass of resin, and concentration of metal ions. The amount of metal‐ion uptake of the polymer was determined by using atomic absorption spectrometry. Results of the study revealed that the resin exhibited higher capacities and a more pronounced adsorption toward Pb²⁺ and that the metal‐ion uptake follows the order: Pb²⁺ > Cu²⁺ > Zn²⁺ > Ni²⁺. The adsorption and binding capacity of the resin toward the various metal ions investigated are discussed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Metal ion exchange in dinuclear macrocyclic complexes identified by electrospray mass spectrometry

Dicopper(I) complexes of a two-compartment 34-membered bis-dithiadiimine macrocycle (1) in solution in the presence of silver(I) ion display in electrospray mass spectrometry experiments the presence of AgCu(1)²⁺ and Ag₂(1)²⁺ in addition to the original Cu₂(1)²⁺, consistent with metal ion exchange in this helical complex occurring without fragmentation.     

A semi‐aza‐crown‐based chemosensor for colorimetric detection of iron(III) and iron(II) in aqueous media with large bathochromic shift

A colorimetric chemosensor, EDDAN (1,1′‐((1E,11E)‐5,8‐dioxa‐2,11‐diazadodeca‐1,11‐diene‐1,12‐diyl)bis(naphthalen‐2‐ol)), based on a semi‐aza‐crown structure, was designed and synthesised to sense iron(III) and iron(II). EDDAN showed a unique colour change in the presence of either iron(III) or iron(II), turning from pale yellow to deep purple with large bathochromic shifts. The detection limits of iron(III) and iron(II) were 2.70 and 3.43 μm , respectively. EDDAN displayed a high selectivity for iron ions in the presence of other metal cations except copper(II). In addition, EDDAN showed excellent reversibility by using ethylenediaminetetraacetic acid. Moreover, EDDAN was applied to test strips as well. Based on ultraviolet‐visible titrations, Job plots, electron paramagnetic resonance study and electrospray ionisation mass spectrometry analyses, a mechanism for the sensing of iron(III) and iron(II) was also proposed.     

A highly selective chemosensor for Cu and Al in two different ways based on Salicylaldehyde Schiff

A novel, easily available colorimetric and fluorescent double-sensor 1 based on Salicylaldehyde bis-Schiff has been investigated in this work. The sensor exhibits highly selective and sensitive recognition toward Cu²⁺ in aqueous solution via a naked eye colour change from colourless to yellow and toward Al³⁺ via a significant fluorescent enhancement in ethanol over a wide range of tested metal ions. This represents the first reported Salicylaldehyde Schiff-based sensor capable of detecting both Cu²⁺ and Al³⁺ using two different modes.     

Lipid peroxidation in low density lipoproteins from human plasma and egg yolk promotes accumulation of 1-acyl analogues of platelet-activating factor-like lipids

Oxidative modification of low density lipoprotein (LDL) is known to be a key event for induction of atherosclerosis. However, there has been little progress in structural elucidation of oxidized lipids, especially oxidatively fragmented phospholipids retaining a glycerol backbone. In this study, we found that LDL derived from egg yolk has no platelet-activating factor (PAF) acetylhydrolase activity, and that prolonged incubation of egg yolk LDL with Cu²⁺ resulted in the formation of various PAF-like lipids: 1-acyl type phosphatidylcholines with ansn-2-short-chain dicarboxylate or monocarboxylate group. Only a very small amount of the PAF-like lipid having ansn-2-short-chain monocarboxylate group was detected by gas chromatography-mass spectrometry in Cu²⁺-oxidized LDL from human plasma with high PAF-acetylhydrolase activity, which has been reported to hydrolyze PAF-like lipids to lysophosphatidylcholines. Preincubation of plasma LDL with diisopropyl fluorophosphate dose-dependently inhibited PAF-acetylhydrolase activity, resulting in accumulation of the PAF-like lipids when the LDL was oxidized with Cu²⁺. As well as PAF and lysophosphatidylcholines, several PAF-like lipids were found to inhibit [³H]thymidine incorporation into cultured vascular smooth muscle cells derived from rat aorta. The possible formation of PAF-like lipids by lipid peroxidation in LDL is discussed as well as its possible significance for induction of atherosclerosis.     

Mass Spectrometry of the Lithium Adducts of Diacylglycerols Containing Hydroxy FA in Castor Oil and Two Normal FA

Castor oil can be used in industry. The molecular species of triacylglycerols containing hydroxy fatty acids (FA) in castor oil have been identified. We report here the identification of twelve diacylglycerols (DAG) containing hydroxy FA in castor oil using positive ion electrospray ionization mass spectrometry of the lithium adducts. They were RR (diricinolein, R is ricinoleate), RL, RS, R‐diOH18:0, R‐diOH18:1, R‐diOH18:2, R‐triOH18:0, R‐triOH18:1, R‐triOH18:2, diOH18:0‐diOH18:1, diOH18:1‐diOH18:1 and diOH18:1‐diOH18:2. The MS² fragment ions, [M + Li ? FA]⁺ and [FA + Li]⁺, from the lithium adducts of DAG containing hydroxy FA (one or two hydroxy FA), were used for the identification. The additional fragment ions from the neutral losses of FA lithium salts [M + Li ? FALi]⁺ were used for the identification of eleven DAG containing two normal FA in a soybean oil bioconversion product. The MS² fragment ions from the neutral losses of FA lithium salts [M + Li ? FALi]⁺ were not detected from the DAG containing hydroxy FA. The DAG containing FA with more hydroxyl groups than the other FA on the same DAG molecule tended to have a prominent fragment ion [FA + Li]⁺ and an undetectable fragment ion [M + Li ? FA]⁺ while the FA was the more hydroxylated FA. Also the less hydroxylated FA of a DAG tended to have a prominent fragment ion [M + Li ? FA]⁺ and an undetectable fragment ion [FA + Li]⁺ while the FA was the less hydroxylated FA.     

A Combined Experimental and Theoretical Study of HMX (Octogen,Octahydro‐1,3,5,7‐Tetranitro‐1,3,5,7‐Tetrazocine) in the Gas Phase

The structures of α‐ and β‐HMX were fully optimized and the vibrational frequencies computed at the hybrid DFT B3LYP/6‐31G(d, p) level of theory. The DCI+mass spectrum of HMX using ammonia (NH₃) as a “soft” ionising gas is reported. Field desorption mass spectrometry (FD) was used because of the high molecular intensities and low fragmentation. The FD spectrum shows only one significant peak at m/e 297 due to the protonated molecular ion [M+H]⁺. These observations clearly establish that under the conditions of CI and FD mass spectrometry experiments HMX is present in the gas phase (without decomposition) prior to the chemical ionisation.     

Turn-on selective fluorescent probe for trivalent cations

A novel fluorescent sensor 1 (1 = 10-(2-(((pyridin-2-yl)methylamino)methyl)phenol)methyl-anthracene) for trivalent cations has been synthesized and characterized. Both UV-vis and fluorescence spectroscopic studies demonstrated that the new receptor 1 was highly sensitive and selective toward trivalent cations, while there was no response to monovalent and divalent cations in methanol. Upon binding with trivalent cations, the emission bands of 1 red-shifted for all the trivalent cations from 411 nm to 421 nm and their fluorescence intensities were enhanced. In particular, Fe^3 + could be obviously discriminated from Fe^2 +. The binding modes of 1 and the trivalent cations (M^3 + ions) were found to be 1:1 and confirmed by Job plot, ¹H NMR titration and ESI-mass spectrometry analysis.     

Accurate mass determination of melamine–formaldehyde synthetic polymers after separation on preparative HPLC

Separation of 57 species from solutions of commercial melamines and analysis by high resolution mass spectrometry using electrospray ionisation and atmospheric pressure chemical ionisation is reported. Structures for melamine-based crosslinked polymers were also confirmed with two orthogonal techniques for characterisation of polymers: Fourier Transform Infrared Spectrometry (FTIR) and Nuclear Magnetic Resonance spectroscopy (NMR), respectively.Accurate mass measurements of melamine–formaldehyde resin structures were achieved in the ppm range, using an internal calibration standard reserpine. Results were within 5 ppm of calculated formulae. Relative isotopic abundances of [M+H]⁺ ions were evaluated for different fractions. Results were independent of the mobile phase used. NMR studies also confirmed structures of fractions and their thermal stability up to 70 °C. Differences in NMR spectra were explained by change of conformation and it was confirmed that this is a reversible process by reheating samples. Stability at 70 °C was confirmed by MS, since when the temperature of the ion transfer capillary in MS was set above this temperature decomposition occurred.     

Analysis of lipoxygenase-derived fatty acid hydroperoxides by electrospray ionization tandem mass spectrometry

A rapid method is described for the identification of fatty acid hydroperoxides by electrospray ionization-tandem mass spectrometry coupled to liquid chromatography without any derivatization required prior to analysis. Localization of fatty acid hydroperoxides in complex mixtures was achieved by monitoring the loss of hydrogen peroxide using constant neutral loss scanning. In the presence of 5 mM NH₄OAc in methanol-water, adductions [M+NH₄]⁺ were formed almost exclusively, directly revealing the molecular mass of the thermolabile hydroperoxides. In addition, low energy collision-induced dissociation of precursor ions [M+NH₄]⁺ led to characteristic product ions from both the 9- and 13-regioisomers. Thus, electrospray ionization-tandem mass spectrometry provides a straightforward approach for the study of the regioselectivity of lipoxygenase catalysis without any derivatization step required prior to analysis.     

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., Job's 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⁺.     

Spiroheterocyclic system. Part IV: Novel azo dye sulpha drugs of spiroheterocyclic naphthenes

Novel azo-dyes have been synthesized by diazotization of 4-amino benzene-4′-(substituted heterocyclo) sulphonamide derivatives and coupling with 1-oxa-4-thia-spiro[4,4]nonan-2-one (I) and/or with l-oxa-4-thia-spiro[4,5]decan-2-one (I′) in acid medium to give the corresponding 3-azo-(4′-substituted benzenesulphonamido)-l-oxa-4-thia-spiro[4,4]nonan-2-one (II-IX) and/or l-oxa-4-thia-spiro[4,5]decan-2-one (II′-IX′] as spiro-ligands. Treatment of these ligands with metal salts of iron (Fe³⁺), copper (Cu²⁺) and mercury (Hg²⁺) as chlorides in ethanolic solution furnished the corresponding metal chelates (II_a-c-IX_a-c) and/or (II′_a-c-IX′_a-c). The compounds were tested in vitro for antimicrobial activity to study the structure-activity relationship.     

Synthesis,Characterization, and Exploration of Antimicrobial Activity of Copper Complex of Diamide Derivative of p-tert-butylcalix[4]arene

Calixarenes are a versatile class of compounds, which possesses wide applications in various fields including biological as well as pharmaceutical sciences. In the present study, amide derivative of calix[4]arene (3) was synthesized and characterized by modern analytical techniques such as elemental analysis and Fourier transform infrared spectroscopy (FT-IR). Complexation property of 3 with essential metals was explored by UV-Vis spectroscopy. The results revealed that 3 shows good selectivity toward Cu²⁺. Job's plot analysis suggests that 3 forms complex with Cu²⁺ in 1:2 stoichiometric ratio. Antimicrobial activity of 3 and its Cu²⁺ complex was also determined and it was observed that 3 is more efficient against R. stolonifer as compared to its action against bacteria, because for fungus it shows “Minimum Inhibitory Concentration” (MIC) value equal to 1.5 µg/mL, while for bacteria MIC is 3 µg/mL. However, it was found that complex is more efficient in action than 3. Oxidation state of metal, overtone concept, and Tweedy's chelation theory justifies the increased activity of metal complex. Cu²⁺ complex shows higher antimicrobial activity toward Escherichia coli (E. coli) (Gram-negative) bacteria by showing MIC value 0.37 µg/mL. While for Staphylococcus albus (S. albus) (Gram-positive) bacteria and Rhizopus stolonifer (R. stolonifer) fungal species, it shows MIC value equal to 0.75 µg/mL.     

Synthesis and chelating properties of poly[(N,N-dicarboxymethyl)allylamine] derived from poly(allylamine)

Summary Poly[(N,N-dicarboxymethyl)allylamine] as a water-soluble polymeric chelating agent was prepared by carboxymethylation of poly(allylamine) (PAA) with chloroacetic acid or bromoacetic acid. The ¹H-NMR, IR, and elementary analyses showed that the iminodiacetic group was introduced quantitatively into the amino group of PAA. Chelating properties of this polymeric chelating agent toward Cu²⁺, Ni²⁺, Zn²⁺, and Ba²⁺ were examined by potentiometric titration.     

Crown ethers appended copper tetraazamacrocyclic complexes as receptors for cationic guests

Tetraazamacrocyclic copper(II) complexes linked by the system of conjugated double bonds with one or two benzo-15-crown-5 ether moieties (4Cu and 5Cu) as well as model compounds were synthesized and characterized. The CV of these complexes in acetonitrile (ACN) solution exhibited reversible Cu^II/I redox process. Complexation of Na⁺ and Mg²⁺ cations with 5Cu in the gas phase was confirmed by electrospray mass spectrometry. In solution complexation of Li⁺ and Na⁺ with 5Cu was weak. Complexation of Cl⁻ anion to coordinated copper in 5Cu resulted in an appreciable shift in the Cu^II/I redox potential after addition of studied cations. The addition of increasing amounts of Mg²⁺ cation to the solution of 5Cu resulted in a significant shift of the Cu^II/I reduction process accompanied by further reduction to Cu⁰ followed by replacement of copper by Mg²⁺ cation. Barium(II) cation interacted only with reduced (Cu⁺) form of 5Cu.