Subnanomolar determination of a beryllium ion by a novel Be(II) microsensor based on 4-nitrobenzo-9-crown-3-ether

In this work, for the first time, we introduce a highly selective and sensitive Be(II) microsensor. 4-nitrobenzo-9-crown-3-ether (NBCE) was used as a membrane-active component to prepare a Be(II)-selective polymeric membrane microelectrode. The electrode exhibits a Nernstian response toward Be(II) ions over a very wide concentration range (1.0 × 10⁻⁴–1.0 × 10⁻¹⁰ M), with a detection limit of 3.5 × 10⁻¹¹ M (∼350 pg/L). In fact, the electrode presents a fast response time in the whole concentration range (6 s). The proposed microelectrode can be used for at least six weeks without any considerable divergence in the potentials. The proposed membrane sensor revealed a selectivity toward Be(II) ions over a wide variety of other metal ions including common alkali, alkaline-earth, and rare-earth ions. It could be used in the pH range of 3.0–11.5. The microelectrode was successfully used as an indicator electrode for the titration of 20 mL of 1.0 × 10⁻⁶ M Be²⁺ solution with 1.0 × 10⁻⁴ M of EDTA. It was also applied to the direct determination of beryllium ions in beryl and binary mixtures. The text was submitted by the authors in English.     

Design and characteristics of tin (II) optode based on immobilization of dithizone on a triacetylcellulose membrane and its application in canned foods

Abstract  

The characterization of an optical sensor membrane is described for the determination of tin (II) based on the immobilization of dithizone on a triacetylcellulose membrane. The membrane responds to tin (II) ions by changing color reversibly from green to red in buffer solution at pH 6 and wavelength 611 nm. This optode has a linear range of 0.3–6.33 μg cm⁻³ (2.52–53.32 μmol dm⁻³) of Sn²⁺ ions with a limit of detection of 0.15 μg cm⁻³ (1.26 μmol dm⁻³). The response time of the optode was about 8–10 min depending on the concentration of Sn²⁺ ions. The selectivity of the optode to tin (II) ions at pH 6 was good. The sensor can be readily regenerated by exposure with EDTA solution. The color is fully reversible, and the optical sensor could be fully regenerated. Experimental results showed that the optode could be used as an effective tool in analyzing the tin content in canned foods.     

Selective lanthanum ions optical sensor based on covalent immobilization of 4-hydroxysalophen on a hydrolyzed triacetylcellulose membrane

An optical sensor membrane is described for the determination of lanthanum(III) ions based on the immobilization of 4-hydroxysalophen on a hydrolyzed triacetylcellulose membrane. 4-Hydroxysalophen is covalently bonded to a transparent hydrolyzed triacetylcellulose film. The sensing membrane in contact with lanthanum ions at pH 4.0 changes color from white-yellow to orange (323 to 433 nm). Under the optimum conditions, the proposed membrane displayed a linear range from 1.0 × 10⁻⁶ to 1.0 × 10⁻² M La(III) with a limit of detection of 1 × 10⁻⁷ M. The response time of the membrane was within 5–6 min depending on the concentration of La(III) ions. The selectivity of the probe towards lanthanum ions was found to be excellent. The sensor was successfully applied to the determination of La(III) in water, industrial waste water, and in NIST-615 (glass matrix) and NIST-3127a (lanthanum solution) samples with satisfactory results.     

A PVC plasticized membrane sensor for nickel ions

A new PVC membrane sensor, which is highly selective towards Ni (II) ions, has been developed using a thiophene-derivative Schiff base as the ionophore. The best performance was exhibited by the membrane having the composition percentage ratio of 5:3:61:31 (ionophore:NaTPB:DBP:PVC) (w/w), where NaTPB is the anion excluder, sodium tetraphenylborate and DBP is the plasticizing agent (dibutyl phthalate). The membrane exhibited a good Nernstian response for nickel ions over the concentration range of 1.0 × 10⁻¹–5.0 × 10⁻⁶ M (limit of detection is 1.8 × 10⁻⁶ M) with a slope of 29.5 ± 1.0 mV per decade of activity. It has a fast response time of <20 s and can be used for a period of 4 months with good reproducibility. The sensor is suitable for use in aqueous solutions of a wide pH range of 3.2–7.9. The sensor shows high selectivity to nickel ions over a large number of mono-, bi- and trivalent cations. It has been successfully used as an indicator electrode in the potentiometric titration of nickel ions against EDTA and also for direct determination of nickel content in real samples – wastewater samples from electroplating industries and Indian chocolates.     

Construction of different types of ion-selective electrodes and validation of direct potentiometric determination of phenytoin sodium

The construction and performance characteristics of phenytoin sodium selective electrodes are detailed. Two types of electrodes: plastic membrane I and coated wire II, were constructed based on the incorporation of phenytoin sodium with tungstosilicic acid. The influence of membrane composition, kind of plasticizer, pH of the test solution, soaking time and the electrodes’ foreign ions were investigated. The electrodes showed a Nernstian response with a mean calibration graph slope of 30.9±0.1 and 28.9±0.1 mV decade⁻¹ at 25°C for electrode I and II respectively, over a phenytoin sodium concentration range of 5×10⁻³−5×10⁻⁶ M and 1×10⁻³−1×10⁻⁶ M with a detection limit 1.3×10⁻⁶ M and 2.5×10⁻⁷ M for electrode I and II, respectively. The electrodes gave average selective precision and were usable within the pH range 6–10. Interference studies from common cations, alkaloids, sugars, amino acids and drug excipients are reported. The results obtained by the proposed electrodes were also applied successfully for the determination of the drug in pharmaceutical preparations and biological fluids.     

Utilization of a spiropyran derivative in a polymeric film optode for selective fluorescent sensing of zinc ion

Spiropyrans are the most studied families of func- tional materials due to their reversible structural con- version in response to external optical, chemical, and thermal stimulation[1]. Irradiation with ultraviolet light causes formation of an extended π-conjugation open form (merocyanine form) by heterolytic cleavage of the C (spiro)-O bond, which generates an intense ab- sorption in the visible region. Under the irradiating of visible light, the opened form will come back to the closed spi…     

Fabrication of an iron(III)-selective PVC membrane sensor based on a bis-bidentate Schiff base ionophore

A Fe³⁺ ion-selective membrane sensor was fabricated from polyvinyl chloride (PVC) matrix membrane containing bis-bidentate Schiff base (BBS) as a neutral carrier, sodium tetraphenyl borate (NaTPB) as anionic excluder, and o-nitrophenyloctyl ether (NPOE) as a plasticizing solvent mediator. The effects of the membrane composition, pH, and additive anionic influence on the response properties were investigated. The best performance was obtained with a membrane containing 32% PVC, 62.5% NPOE, 3% BBS, and 2.5% NaTPB. The electrode shows a Nernstian behavior (slope of 19.3 ± 0.6) over a very wide iron ion concentration range (1.0 × 10⁻⁷–1.0 × 10⁻² M) and has a low detection limit (7.4 × 10⁻⁸ M). The potentiometric response of the sensor is independent of pH of the solution in the pH range 1.9–5.1. The proposed sensor has a very low response time (<15 s) and a good selectivity relative to a wide variety of other metal ions including common alkali, alkaline earth, heavy, and transition metal ions. The electrode can be used for at least 60 days without any considerable divergence in potentials. The proposed sensor was successfully applied as an indicator electrode for the potentiometric titration of 1.0 × 10⁻² M Fe³⁺ ions with a 1.0 × 10⁻⁴ M EDTA and the direct determination of Fe³⁺ in mineral water and wastewater samples.     

Cobalt(II)-selective membrane sensor based on a [Me2(13)dieneN4] macrocyclic cobalt complex

A new poly(vinyl chloride)-based membrane was fabricated with the cobalt(II) complex of 2,4-dimethyl-1,5,8,11-tetraazacyclotrideca-1,4-diene [Me₂(13)dieneN₄] as an ion carrier. The membrane composition was Co²⁺ complex/PVC/NaTPB/DBP 15:50:15:20 (w/w). The sensor exhibited a Nernstian response for Co²⁺ ions over a wide concentration range (7.94×10⁻⁶–1.0×10⁻¹ M) at pH 2.5–7.0, a response time of 10 s, and it could be used for 3 months without any significant divergence in potential. The proposed membrane sensor exhibited good selectivity for Co²⁺ over a wide variety of other metal ions and in mixtures containing up to 25% (v/v) non-aqueous content. The sensor was successfully used as an indicator electrode in the potentiometric titration of Co²⁺ with EDTA and the direct determination of Co²⁺ in real samples.     

Differential pulse polarographic determination of Co(II) using moxifloxacine

The polarographic reduction of Co(II) in the presence of moxifloxacin (1-cyclopropyl-7-[(S,S)-2.8-diazabicyclo[4.3.0]non-8-yl]-6-fluoro-8-methoxy-1.4-dihydro-4-oxo-3-quinolinecarboxylic acid) gives rise to an additional adsorption peak corresponding to the reduction of Co(II)-moxifloxacin complex on the mercury drop electrode at −1.17 V. This new peak is applicable to Co(II) determination with the linearity proportional to the Co(II) concentration in the range of 4.93 × 10⁻⁷−6.90 × 10⁻⁵ M and can be attributed to an adsorption-controlled process with an irreversible reduction. Without using moxifloxacin, the polarographic determination of 2.50 × 10⁻⁶ M Co(II) is impossible under the given conditions due to very poor sensitivity at −1.38 V. The proposed method showed good precision and accuracy with a relative standard deviation of 3.01% and relative error of +6.40% for the determination of 2.50 × 10⁻⁶ M Co(II) next to 5.0 × 10⁻⁶ M of Zn(II), Ni(II), and Cd(II). The accuracy of the method was also checked by the determination of Co(II) spiked with tap water and certified sea water, and the percentage recoveries were 97.5 and 96.7%, respectively (n = 4 at 95% confidence interval). The text was submitted by the authors in English.     

Aluminium(III)-selective electrode based on a newly synthesized glyoxal-<Emphasis Type="Italic">bis</Emphasis>-thiosemicarbazone Schiff base

A PVC membrane electrode for Al³⁺ based on glyoxal-bis-thiosemicarbazone (GBTC) as an ion carrier was developed. The electrode exhibits a Nernstian slope of 20.1 mV per decade and a linear range of 1.8 × 10⁻⁵−1.0 × 10⁻¹ M for Al(NO₃)₃ with a detection limit of 8.7 × 10⁻⁶ M. It has a fast response time of about 10 s and can be used for at least 1 month. The proposed membrane sensor revealed a good selectivity for Al³⁺ over a wide variety of other metal ions and could be used in the pH range of 2.5–4.5. The text was submitted by the authors in English.     

Determination of copper(II) in wastewater by electroplating samples using a PVC-membrane copper(II)-selective electrode

A PVC membrane containing 4-amino-6-methyl-1,2,4-triazin-3,5-dithione (AMTD) as a suitable ionophore, exhibits a Nernstian response for Cu²⁺ ions over a wide concentration range up to 1 × 10⁻¹ and 1 × 10⁻⁶ M, with a detection limit of 7.5 × 10⁻⁷ M in the pH range 3.0–7.5. It has a fast response time (<15 s) and can be used for at least 12 weeks without any major deviation in the potential. The electrode revealed a very good selectivity with respect to all common alkali, alkaline-earth, transition, and heavy-metal ions. It was successfully applied to the recovery of copper ions from wastewater. The electrode was also used as an indicator electrode in the potentiometric titration of Cu(II) ions with EDTA. The text was submitted by the authors in English.     

Cobalt(II) ion-selective electrode with solid contact

A new all plastic sensor for Co²⁺ ions based on 2-amino-5 (hydroxynaphtyloazo-1′)-1,3,4 thiadiazole (ATIDAN) as ionophore was prepared. The electrode exhibits a low detection limit of 1.5 × 10⁻⁶ mol L⁻¹ and almost theoretical Nernstian slope in the activity range 4.0 × 10⁻⁶–1 × 10⁻¹ mol L⁻¹ of cobalt ions. The response time of the sensor is less than 10 s and it can be used over a period of 6 months without any measurable divergence in potential. The proposed sensor shows a fairly good selectivity for Co(II) over other metal ions. The electrode was successfully applied for determination of Co²⁺ in real samples and as an indicator electrode in potentiometric titration of Co²⁺ ions with EDTA.      

Development of a new flow-through bulk optode for the determination of manganese(II)

A flow-through bulk optode based on the use of 1-(2-pyridylazo)-2-naphthol (PAN) immobilized in a plasticized poly(vinyl chloride) membrane entrapped in a cellulose support, in conjuntion with the flow injection analysis technique, is proposed for the determination of manganese(II). The calibration graph obtained at 570 nm was linear in the range 0.27–27.5 mg L^–1 (5 × 10^–6– 5 × 10^–4 M) Mn(II) with a detection limit of 0.18 mg L^–1. The coefficients of variation of the sensor response for 5.5 mg L^–1 of Mn(II) were ±0.22% for consecutive measurements (n = 10), ±0.48% between days (n = 5) and ±0.38% between different membranes (n = 6). The sensor was readily regenerated with the carrier acetic acid/acetate buffer of pH 4.5. The method was applied to the determination of manganese in steels, waters and lemon tree leaves. Received: 13 December 2000 / Revised: 25 January 2001 / Accepted: 26 January 2001     

PVC-based Cu (II)-Schiff base complex membrane coated graphite electrode for the determination of the triiodide ion

A triiodide-selective electrode based on copper (II)-Schiff base complex as a membrane carrier is proposed. The electrode was prepared by incorporating the carrier into a plasticized polyvinylchloride (PVC) membrane and was directly coated on the surface of a graphite electrode. The obtained electrode showed a near Nernstian slope of 57.0 ± 0.4 mV/decade to I ₃ ⁻ ions over an activity range of 1.0 × 10⁻⁵−1.0 × 10⁻¹ M with a limit of detection of 4.8 × 10⁻⁶ M. The response time of the electrode was fast (5 s) and the electrode could be used for about 2 months without considerable divergence in response. The potentiometric selectivity coefficients were evaluated and displayed anti-Hofmeister behavior. The electrode was used as an indicator electrode in the potentiometric titration of the triiodide ion and in the determination of ascorbic acid in vitamin C tablets. The text was submitted by the authors in English.     

Quartz Crystal Microbalance for Selenite Sensing Based on Growth of Cadmium Selenite Crystals Immobilized on a Monolayer of Phosphorylated 11-Mercapto-1-Undecanol

 A quartz crystal microbalance (QCM) sensor for selenite ions in aqueous solution was constructed based on crystal formation of cadmium selenite, immobilized with a self-assembly monolayer (SAM) of phosphorylated 11-mercapto-1-undecanol (MUD) on a QCM gold electrode surface. The mass change caused by the selective adsorption of selenite ions on the cadmium selenite crystals at the solid/solution interface was detected by the QCM. The response (−ΔF) of the modified QCM oscillator increased with increasing selenite ion concentrations in sample solutions, ranging from 9.7×10⁻⁵ to 9.0×10⁻⁴ M at pH 7.4. The synthetic process of anchoring cadmium selenite crystals on the phosphorylated MUD organic film was also followed by using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The atomic concentrations measured by XPS confirmed the crystal growth of cadmium selenite on the phosphorylated MUD SAM at the QCM gold electrode surface. From the AFM images, changes in surface topographic features were followed: the MUD SAM and phosphorylated MUD on the QCM gold electrode had similar surface roughness; however the difference for the cadmium selenite film on the phosphorylated MUD SAM was clearly seen. The observed QCM frequency change of the modified QCM oscillator per unit time was found to be proportional to the square of the supersaturation of cadmium selenite, indicating the crystal growth of cadmium selenite at the solid/solution interface. The modified QCM oscillator exhibited selectively strong QCM response to SeO₃ ²⁻ ion. In contrast, the responses to tested interfering anions were almost negligible. The order of anion selectivities of the present modified QCM sensor was SeO₃ ²⁻≫CO₃ ²⁻>SeO²⁻ ₄, SO₄ ²⁻, Br⁻, I⁻, NO₃ ⁻. These selectivities were basically attributable to the differences in solubility products and solubilities for the salts of each anion with cadmium (II) ion. Received May 12, 1998. Revision December 29, 1998.     

A kinetic method for the determination of organosulfur compounds by inhibition: determination of cysteine, 2,3-dimercaptopropanol and thioglycolic acid

A kinetic method for the determination of organosulfur compounds by UV spectrophotometry is described. Organosulfur compounds have been shown to inhibit the Hg(II)-catalyzed substitution of cyanide in hexacyanoferrate(II) by 2-methylpyrazine (2-Mepz). The inhibitory effect is proportional to the concentration of inhibitor and can be used as the basis for the determination of trace amounts of organosulfur compounds such as cysteine, 2,3-dimercaptopropanol (DMP) and thioglycolic acid (TGA). Both the influence of the reaction variables and interference of a variety of ions have been studied. A mechanism for the inhibition process is proposed. The determination range depends on the amount of Hg(II) added and stability of the Hg(II)–ligand complex. Kinetic parameters were determined from Lineweaver–Burk plots, obtained in the absence and presence of the inhibitor. Excellent linearity is observed for all analytes over their respective concentration ranges with correlation coefficient >0.9. The condition calibration curves were linear in the range of 5 × 10⁻⁶–15 × 10⁻⁶ M for cysteine, 1 × 10⁻⁷–7 × 10⁻⁷ M for DMP and 1 × 10⁻⁶–10 × 10⁻⁶ M for TGA. The detection limits were 1.18 × 10⁻⁷ M for cysteine, 4.16 × 10⁻⁸ M for DMP and 1.30 × 10⁻⁷ M for TGA. The effects of amino acids that can interfere in the determination of cysteine were studied.     

Mercury-selective membrane electrode based on methyl substituted dibenzo tetraphenyl tetraaza macrocycle

A new polystyrene based membrane electrode of methyl substituted 6,7:13,14-dibenzo-2,4,9,11-tetraphenyl-1,5,8,12-tetraazacyclotetradeca-1,4,6,8,11,13-hexaene (I) with sodium tetraphenylborate (NaTPB) and dibutyl phthalate (DBP) as anion excluder and plasticizing agent was prepared and investigated as Hg (II)-selective electrode. The electrode exhibits a Nernstian response for Hg (II) ions over a wide concentration range of 1.0 × 10⁻¹–8.9 × 10⁻⁶ M with a slope of 30 ± 1 mV per decade concentration. It has a response time of 10 s and can be used for at least 4 months without any divergence in potentials. The membrane works satisfactorily in a partially non-aqueous medium up to a maximum 30% (v/v) content of methanol and ethanol. The proposed sensor revealed good selectivity over a wide variety of other cations including alkali, alkaline earth, heavy and transition metal ions and could be used in a pH range of 2.5–5.0. Normal interferents like Ag⁺, Cd²⁺ and Pb²⁺ low interfere in the working of the electrode. The electrode was successfully used in the direct determination of Hg²⁺ in aqueous solution.     

A new sensitive optical bulk test-system for thallium based on pyridylazo resorcinol

A color changeable optode for thallium(III) ions in aqueous solutions was prepared by physical inclusion of 4-(2-pyridylazo)-resorcinol into a plasticized PVC film. The increase in the absorbance of the optode at 524 nm is proportional to thallium(III) concentration. Different parameters effecting the sensitivity such as sample parameters and composition of the membrane were optimized. The response times of the prepared test-system are found to be 230, 210, and 180 s for 4.8 × 10^?6, 4.8 × 10^?5, and 4.8 × 10^?4 M Tl(III), respectively. The analytical performance of the optode was evaluated, obtaining a linear concentration range of two decades of concentration, 3.1 × 10^?6 ? 4.7 × 10^?4 M Tl(III), with a limit of detection of 1.8 × 10^?6 M Tl(III). Selectivity of the optode is also studied. Application of the optode to the determination of Tl(III) in some aqueous samples yields good results.     

Comparative Studies of Tridentate Sulfur and Nitrogen‐Containing Ligands as Ionophores for Construction of Cadmium Ion‐Selective Membrane Sensors

New polymeric membrane cadmium‐ion selective sensors have been prepared by incorporating nitrogen and sulfur containing tridentate ligands as the ionophores into the plasticized PVC membranes. Poly(vinyl chloride) (PVC) based membranes of potassium hydrotris[N‐(2,6‐xylyl)thioimdazolyl) borate] (KTt^2,6‐xylyl) and potassium hydrotris(3‐phenyl‐5‐methylpyrazolyl) borate (KTp^Ph,Me) with sodium tetraphenyl borate (NaTPB) as an anionic excluder and dibutylphthalate (DBP), tributylphthalate (TBP), dioctylsebacate (DOS), and o‐nitrophenyloctyl ether (o‐NPOE) as plasticizing solvent mediators were investigated in different compositions. KTt^2,6‐xylyl was found to be a selective and sensitive ion carrier for Cd(II) membrane sensor. A membrane composed of KTt^2,6‐xylyl:NaTPB:PVC:DBP with the % mole ratio 2.3 : 1.1 : 34.8 : 61.8 (w/w) works well over a very wide concentration range (7.8×10^?8–1.0×10^?2 M) with a Nernstian slope of 29.4±0.2 mV/decades of activity between pH values of 3.5 to 9.0 with a detection limit of 4.37×10^?8 M. The sensor displays very good discrimination toward Cd(II) ions with regard to most common cations. The proposed sensor shows a short response time for whole concentration range (ca. 8 s). The effects of the cationic (tetrabutylammonium chloride, TBC), anionic (sodium dodecyl sulfate, SDS) and nonionic (Triton X‐100) surfactants were investigated on the potentiometric properties of proposed cadmium‐selective sensor. The proposed sensor based on KTt^2,6‐xylyl ionophore has also been used for the direct determination of cadmium ions in different water samples and human urine samples.     

Adsorption of Cu(II), Cd(II), Pb(II), Cr(VI) by double hydroxides on the basis of Al oxide and Zr, Sn, and Ti oxides

It was studied the equilibrium adsorption and adsorption kinetics of Cu(II), Cd(II), Pb(II), and Cr(VI) by composite hydroxides formed by Me _x O _y · nH₂O and Me_0.4–0.7Al_0.6–0.3O _y · nH₂O, where Me = Zr, Sn and Ti. It was estimated the values of the diffusion coefficients of adsorbed ions Cu(II) and Cr(VI) from kinetic values. It was established that the estimated diffusion coefficients of adsorbed ions Cu(II) are in the range 0.4 × 10⁻¹²–2.5 × 10⁻¹² m²/s for individual hydroxides and 1.2 × 10⁻¹²–2.8 × 10⁻¹² m²/s for double hydroxides. The obtained values of diffusion coefficients Cr (VI) for double hydroxides are 0.1 × 10⁻¹⁰–0.4 × 10⁻¹⁰ m²/s.