Sodium ion-selective membrane electrode based on a new crown ether

A sodium ion-selective PVC membrane electrode based on di(o-methoxy)stilbenzo-24-crown-8 is reported. The electrode gives a near-Nernstian response in the range 9×10^?6–1×10^?2 M sodium ion and can be used in the pH range 5–8.5. Selectivity coefficients are 1.8×10^?1 (K⁺), 2.0×10^?4 (Li⁺) 2.5×10^?2 (NH⁺₄) and about 10^?4 for Mg²⁺, Ca²⁺ and Ba²⁺.     

1,4,7,10-Tetraoxacyclododecane(12-Crown-4) as Neutral Carrier for Lithium Ion in Lithium Ion Selective Electrode

Abstract

1,4,7,10-Tetraoxacyclododecane (12-crown-4) (I) and its lithium complex (II) are used as neutral carriers for lithium ion in polyvinylchloride membrane ion selective electrodes. The lithium response varies with concentration, being near Mernstian at low (10^?5-10^?4 M) concentrations and sub-Nernstian (24-28 aV) at higher concentrations (10^?3 M). The selectivity coefficients K_Li ^Pot _M for II are: Na⁺ (0.12), K⁺ (0.66), Cs⁺ (0.15), Mg²⁺ (1.6 × 10^?4), Ca²⁺ (3.1 × 10^?4), Ba²⁺ (9.5 × 10^?7), NH⁺ ₄ (9.0 × 10^?2), H⁺ (2.2).     

A novel rhodamine-based turn-on probe for fluorescent detection of Au3+ and colorimetric detection of Cu2+

In this work, we design and synthesize the novel probe RC through introduction the 1-aza-4,13-dithia-15-crown-5 ring into the structure of rhodamine 6G hydrazide, where the N atom of crown ring is responsible for quenching of rhodamine fluorescence. The compound obtained behaves as multifunctional cation sensor providing selective fluorescent response to Au³⁺ and selective colorimetric response to Cu²⁺ ions in aqueous acetonitrile (1/1, v/v) at pH 7.0. The use of 10^?5?M RC solution allowed reliable determination of target cations in the presence of a wide range of environmentally relevant ions with detection limits of 2?×?10^?6?M and 5?×?10^?7?M for gold and copper, respectively.     

Mercury selective membrane electrode based on dithio derivatized macrotricyclic compound

A novel dithio derivatized macrotricyclic compound (cryptand) has been synthesized using high dilution technique by condensation of diaminodibenzo18-crown-6 with 2, 2′dithiobenzoyl chloride. The compound was characterized by elemental analysis, ¹H NMR, ¹³C NMR and FAB-MS. PVC membrane electrode based on this macrotricyclic compound showed good selectivity for Hg²⁺ ion with a wide linear range of 1.0 × 10^?6 to 1.0 × 10^?1 M and a lower detection limit of 5.0 × 10^?6 M with a calibration slope of 30.2 mV decade^?1. The electrode response was stable in pH range 3–6. Electrode showed good selectivity for Hg²⁺ over other interfering metal ions. The electrode was then applied to direct determination of Hg²⁺ in water samples.     

Magnesium-PVC Membrane Sensor Based on 4,5-Bis(Benzoylthio)-1,3-Dithiole-2-Thione

Abstract

This report describes an attempt to develop potentiometric Mg²⁺ sensors based on a liquid polymeric membrane. Membrane incorporating 4,5-Bis(benzoylthio)-1,3- dithiole-2-thione (Bz₂dmit) as ionophore, with composition Bz₂ dmit:NaTPB:NB:PVC in the ratio 2.5:2.5:65:30 (w/w), exhibits the best result for potentiometric sensing of Mg²⁺ ions. The proposed electrode, based on Bz₂ dmitwith nitrobenzene (NB) as a solvent mediator in a polyvinyl chloride (PVC) membrane matrix, exhibited a near-Nernstian response to Mg²⁺ in the concentration range of 1.0 × 10^?5 to 1.0 × 10^?1 M, with a slope of 29.2 mV per decade of activity of Mg²⁺. The lower limit of detection was 1.0 × 10^?5 M. This sensor showed high selectivity with respect to alkaline, alkaline earth, transition, and heavy metal ions, except for Sr²⁺, and could be used over a pH range of 3.5–9.0. It can be used for at least 2 mo without considerable divergence in potentials and has a relatively fast response of <10 s. It was applied successfully as an indicator electrode in potentiometric titration of Mg²⁺ ions with EDTA.     

Syntheses of diaza-18-crown-6 ligands containing two units each of 4-hydroxyazobenzene,benzimidazole, uracil,anthraquinone, or ferrocene groups

Six new diaza-18-crown-6 ligands each containing two aromatic side arms with responsive functions were prepared. Diaza-18-crown-6 containing two 4-hydroxyazobenzene ( 3 ) or two 4 -hydroxy- 4′ -(dimethyl-amino)azobenzene ( 4 ) substituents were prepared via a one-pot Mannich reaction. Diaza-18-crown-6 containing two benzimidazole ( 5 ), two uracil ( 6 ) or two 9,10-anthraquinone ( 7 ) substituents were prepared by treating the diazacrown with the appropriate chloromethyl-containing compound. Reductive amination using sodium triacetoxyborohydride, diaza-18-crown-6 and ferrocenecarboxaldehyde was used to prepare bisferrocene-substituted diaza-18-crown-6 ( 8 ). Interactions of compounds 3 , 5 , and 6 with Na⁺, K⁺, Ba²⁺, Ag⁺, and Cu²⁺ were evaluated by a calorimetric titration technique at 25° in methanol. All three ligands form more stable complexes with Ag⁺ and Cu²⁺ ( 5 forms a precipitate with Ag⁺) than with Na⁺ and K⁺. Ligand 5 also forms a highly stable complex with Ba²⁺.     

Kinetic Spectrophotometric Determination of Thiols and Ascorbic Acid

Abstract

This paper describes a kinetic spectrophotometric method for the determination of L‐ascorbic acid (AA) and thiols (RSH). Absorbance of Fe(II)‐phen complex formed during the reaction of AA or RSH with Fe(III)‐phen was continuously measured at 510 nm by double‐beam spectrophotometer with flow cell. For determination some thiols, the catalytic effect of Cu²⁺ ions was used. AA and RSH can be determined in concentration ranges from 4.0×10^?6 to 4.0×10^?5 M and from 8.0×10^?6 to 8.0×10^?5 M, respectively. The applicability of the proposed method was demonstrated by determination of chosen compounds in pharmaceutical dosage forms.     

Guanidinium-selective PVC membrane electrodes based on crown ethers

Guanidinium-selective membrane electrodes were constructed with dibenzo-24-crown-8, dibenzo-27-crown-9, tribenzo-27-crown-9 or dibenzo-30-crown-10. The detection limits and selectivity coefficients towards different interfering ions, such as Li⁺, Na⁺, K⁺, NH⁺₄, Mg²⁺ and Ca²⁺ were determined. The electrode with dibenzo-27-crown-9 shows linear response over the range 10^?1–10^?4 M, with selectivity coefficients about 10^?2 for most alkali and alkaline earth metal ions.     

Dependence on pH of the Luminescent Properties of Metal Ion Complexes of 5-Chloro-8-hydroxyquinoline Appended Diaza-18-Crown-6

Luminescent properties of 5-chloro-8-hydroxyquinoline (CHQ) free and appended tothe amines in diaza-18-crown-6 (A₂18C6) were determined. These propertieswere compared to those of bivalent alkaline earth and post-transition metal ioncomplexes of the appended macrocycle (CHQ-A218C6). The luminescent properties were foundto be pH dependent. In the pH range 3 to 7, CHQ-A₂18C6 forms luminescent complexes withonly Zn²⁺ and Cd²⁺. At higher pH values, luminescent complexes wereformed with Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺. No luminescent complex was formed by Hg²⁺ over the pH range studied. This lariat macrocycle could findapplication as a chemosensor for several of the metal ions studied.     

Study of Fluorescence System of Gmanylic Acid-Tb3+ and the Determination of Gmanylic Acid

Abstract

It was found that gmanylic acid (GMP) can be selectively completed with Tb³⁺ at pH 6.0-6.6, which then emits strong fluorescence characteristic of Tb³⁺. This reaction can be used for the determination of GMP in presence of adenylic acid (AMP), uridylic acid (UMP) and cylidylic acid (CMP). A linear relationship is obtained between the fluorescence intensity and GMP concentration in the range of 2.0×10^?7 - 1.0×10^?4M. The detection limit is 2.0×10^?8 M. The results showed that the composition ratio and apparent stability constant of GMP-Tb complex were 1:1 for GMP Tb³⁺- and 2.3×10^?5, respectively.     

A new Schiff base fluorescent indicator for the detection of Mg<Superscript>2+</Superscript> and its application to real samples

A new Schiff base fluorescence probe, 3-Allylsalicylaldehyde salicylhydrazone (L), for Mg²⁺ was designed and synthesized. The fluorescence of the sensor L was enhanced remarkably by Mg²⁺ with 2:1 binding ratio, and the binding constant was determined to be 1.02 × 10⁷ M^?1. Probe L had high sensitivity for Mg²⁺ in a solution of DMF/water (4:1, v/v, pH 7.5), and the detection limit was 4.88 × 10^?8 mol/L. Common coexistent metal ions, such as K⁺, Na⁺, Ag⁺, Ca²⁺, Zn²⁺, Ba²⁺, Bi²⁺, Cu²⁺, Ni²⁺, Hg²⁺, Fe³⁺ , and Al³⁺, showed little or no interference on the detection of Mg²⁺ in solution. The fluorescence probe L, which was successfully used for the determination of trace Mg(II) in real samples, was shown to be promising for liquid-phase extraction coupled with fluorescence spectra.     

Spectrophotometric determination of lithium ion with the chromogenic crown ether, 2″,4″-dinitro-6″-trifluoromethylphenyl-4′-aminobenzo-14-crown-4

A spectrophotometric method of determining alkali metal ions with a chromogenice crown ether reagent was found to be more selective and sensitive than an ion-pairing method based on the same size of crown ether cavity. It is shown that in the ion-pairing method, the sensitivity toward lithium ion was 5.685 × 10^?4 absorbance/mg l^?1, with sodium interfering at 300 mg l^?1. The chromogenic crown ether, 2″,4″-dinitro-6″-trifluoromeethylphenyl-4′-aminobenzo-14-crown-4, was much superior to benzo-14-crown-4. The sensitivity of the chromogenic crown ether was 1.69 × 10^?3 absorbance/mg l^?1. This represents a three-fold increase in sensitivity and less reagent is needed (2 × 10^?4 M for the chromogenic method versus 1.4 × 10^?3 M for ion-pairing). Interference from sodium decreased to 3000 mg l^?1. The reagent was used to determine lithium ion in treated blood serum samples in both a batch and flow injection method and results were compared with data obtained with atomic absorption; excellent agreement was obtained in all cases.     

Study on the Fluorescence System of Oxolinic Acid‐Tb(III) and the Determination of Oxolinic Acid

Abstract

In Tris‐HCl buffer (pH=7.43), Tb³⁺ can react with oxolinic acid (OA) and form a 1:2 complex, which emits the intrinsic fluorescence of Tb³⁺. Based on this, a new fluorimetric method of determination of OA is developed. Under the optimum conditions, the enhanced fluorescence intensity of the system is proportional to the concentration of OA in the range of 1.5×10^?7～2.5×10^?5mol/L, and the detection limit is 5.5×10^?9 mol/L. Recovery test was also satisfactory. The experiments indicated that the luminescence mechanism was attributed to the M*–M luminescence.     

A ratiometric fluorescent probe for zinc ions based on the quinoline fluorophore

A ratiometric fluorescent zinc probe 1 of carboxamidoquinoline with a carboxylic acid group was designed and synthesised. Probe 1 exhibits high selectivity for sensing Zn²⁺; about a 13-fold increase in fluorescence emission intensity and an 82?nm red-shift of fluorescence emission are observed upon binding Zn²⁺ in EtOH/H₂O (1?:?1, V/V) solution. The ratiometric fluorescence response is attributed to the 1?:?1 complex formation between probe 1 and Zn²⁺ which has been utilised as the basis for the selective detection of Zn²⁺. The analytical performance characteristics of the proposed Zn²⁺-sensitive probe were investigated. The linear response range covers a concentration range of Zn²⁺ from 2.0?×?10^?6 to 5.0?×?10^?5?mol?L^?1 and the detection limit is 2.7?×?10^?7?mol?L^?1. The determination of Zn²⁺ in both tap and river water samples shows satisfactory results.     

Spectrophotometric and spectrofluorimetric determination of iodide by extraction of ICl−2 with rhodamine B

Iodide is determined after oxidation with nitrous acid in 5 M hydrochloric acid to ICl^?₂. The ion-pair formed with rhodamine B is extracted into toluene and measured spectrophotometrically (0.5–5 × 10^?5 M) or spectrofluorimetrically (1–10 × 10^?6 M). The relative standard deviations were 1.8% for the determination of 5 × 10^?6 M iodide (n = 5) by spectrofluorimetry and 2.3% (n = 50) for 1 × 10^?5 M iodide by spectrophotometry. Periodate, iodate and iodine responded exactly as iodide.     

Magnesium Ion Selective Electrodes Based on β-Diketone Compounds

Abstract

The ion selectivities for poly(vinyl chloride) (PVC)-matrix membrane ion-selective electrodes based on seven lipophilic diketone compounds were examined. All the electrodes based on the tested five β-diketone cómpounds exhibited clear Mg²′-selectivity under high pH conditions (pH10). Especially, the electrode based on 2-acetyl-1-tetralone shows excellent Mg²⁺-selectivity, and the selectivity coefficients of the Mg²+ -electrode to Ca²+, K⁺ and K⁺ (log K^pot _{mg, ca} log K^pol _mg.k and log K^pot _Mg.Na) in pH 10 solution were ?2.2, ?1.9 and ?2.7, respectively. This elecrode gave a response slope of about 60 mV/pMg²⁺ ranging from 1 × 10^?2 to 2 × 10^?2, which corresponds to twice the usual Nernstian theoretical responce slope for the divalent cation. This phenomenon is advantageous for the acccurate determination of Mg²⁺.     

Fluorescence enhancement by gadolinium of the europium or samarium-dibenzoylmethane-diethylamine system

A fluorescence enhancement produced by adding Gd³⁺, Y³⁺, Tb³⁺, La³⁺ or Lu³⁺ to europium or samarium-dibenzoylmethane-diethylamine was observed. Gd³⁺ enhanced the fluorescence intensity by 2–3 orders of magnitude compared with the system without Gd³⁺. The new system was used for the simultaneous determination of traces of Sm³⁺ and Eu³⁺ in the ranges 1.0 × 10^?9?8.0 × 10^?8 M and 1.0 × 10^?11?4.0 × 10^?9 M, respectively, and the detection limits were 5 × 10^?13 M for Sm³⁺ and 8 × 10^?14 M for Eu³⁺. The luminescence mechanism of the system is discussed.     

Simultaneous determination of silicic acid, Ca, Mg and Al in mineral water and composite tablets by Ion chromatography

Summary A simple, selective and sensitive ion-chromatography method was investigated for simultaneously determining silicic acid, Ca²⁺, Mg²⁺, Al³⁺ and anions (Cl⁻ and NO ₃ ⁻ ) in real samples. It involved a single-column ion-chromatograph with sodium hydroxide-methanol-water eluent and conductometric detection. Cations were converted to complex anions by adding EDTA to the sample solution. A set of well-defined peaks of silicic acid, Ca²⁺, Mg²⁺, Al³⁺, Cl⁻ and NO ₃ ⁻ were obtained. Detection limits using 3.3σ (σ=standard deviation of blank solution) were 1.25×10⁻⁶ M for H₃SiO ₄ ⁻ , 1.32×10⁻⁶ M for Ca²⁺, 1.28×10⁻⁶ M for Mg²⁺, 1.33×10⁻⁶ M for Al³⁺, 1.31×10⁻⁶ M for Cl⁻ and 1.24×10⁻⁶ M for NO ₃ ⁻ . The method was successfully applied to analysis of mineral water and composite tablets.     

A nafion/crown ether film electrode and its application in the anodic stripping voltammetric determination of traces of silver

Glassy carbon electrodes are modified by coating with dicyclohexyl-18-crown-6 in Nafion-117. The electrode is used for a very sensitive anodic stripping voltammetric determination of silver. High sensitivity is obtained owing to the release of crown molecules from the silver-crown complex during the deposition. The detection limit is 2×10^?12 M after electrodeposition for 30 min. The recommended supporting electrolyte is 4×10^?3–7×10^?3 M potassium chloride in 0.01 M nitric acid with a deposition potential of ?0.30 V vs. SCE and a linear potential scan. Three typical calibration graphs were linear over the range 2×10^?11–1×10^?8 M for deposition times of 30, 20 and 8 min, respectively. The silver content of reagent-grade ammonium nitrate was found to be 0.48×10^?4% with a relative standard deviation of 3.7% (n=7) for parallel determinations.     

The Use of the CS2N− 3/HSO− 3/O2 Reaction for the Analytical Determination of Dissolved Oxygen

Abstract

A new analytical Spectrophotometric method has been developed for the determination of dissolved O₂ in the range 4.6 × 10^?6?4.1 × 10^?5M, based on the CS₂N^? ₃/HSO^? ₃/O₂ reaction. In one single experiment 2.3 × 10^?5 M of oxygen can be determined with an uncertainty of ± 7 × 10^?7M for a confidence level of 95%.