A new, efficient Calcium ion selective electrode has been prepared using Schiff base based ionophore.The influence of temperature on electrode potential was studied & it can be used in the determination of thermodynamicfunction like DG, DH & DS.The electrochemical impedance spectroscopy(EIS)technique is also employed to study the electrochemical & surface reactions. It was also successfully used in the analysis of concentration of Calcium ion in various real samples.
In our previous paper using complex of 1,8-diamino-3,6-dioxaoctane nickel(II) percholorate as ionophore for preparing salicylate-selective electrode was described. The optimum composition of the membrane was 29.0 wt.% PVC, 63.0 wt.% dioctylphthalate (DOP) as plasticizer, 6.0 wt.% ionophore, 2.0 wt.% methyltrioctylammonium chloride (MTOAC) as cationic additive. The characteristics of this electrode can be referred to a Nernstian response of -59.5 ± 1.0 mV decade -1 over the concentration range of 7.0×10 -7 - 1.0×10 -1 M salicylate, the detection limit of 5.0×10 -7 M and a wide pH range of 6.0-9.5. The prepared electrode was suitable for measuring the acetylsalicylic acid content in pharmaceutical samples without a significant interaction from concomitant anionic species. The results show that there was a coordination interaction between salicylate and the proposed carrier, which played an important role in the response characteristics and selectivity of the electrode .
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In this part, the construction of plasticised PVC desvenlafaxine-ion selective electrode and its application in pharmaceutical analysis and in urine are described. Desvenlafaxine HCl (DVN), 1-2-(dimethylamino)-1-(4- methoxyphenyl) ethyl-cyclohexanol hydrochloride (Figure 1) is a new phenethylamine bicyclic antidepressant, which has a neuropharmacologic profile distinct from that of existing antidepressants including tricyclic compounds. It imparts antidepressant effects by inhibiting the neuronal uptake of norepinephrine, serotonin and dopamine and lacks the adverse side effect profile of tricyclic antidepressants DVN is well absorbed in humans and undergoes extensive metabolism in the liver and has several metabolites, one of which is biologically active. DVN is extensively metabolized to O-desmethyl venlafaxine (ODV), a major metabolite with an activity profile similar to that of DVN. It is therefore important to monitor plasma concentration of DVN to establish pharmacokinetic parameters.
Eelec, mV) were plotted after 0.5, 1.0, 1.5, 2.0, 3.0, 4.0, 5.0 and 6 h. The optimum soaking time was found to be 0.5-3 hr, at which the slopes of the calibration curves were 54.0-58.0 mV per concentration decade, at 25 °C. Soaking for longer than 8 h is not recommended to avoid leaching, though very little, of the electroactive species into the bathing solution. The electrode should be kept dry in an opaque closed vessel and stored in a refrigerator while not in use. The reproducibility of five repeated measurements on the same solution was ± 1 mV. The duloxetine selective electrode worked for at least 30 – 40 days, during which time no appreciable change in the calibration characteristics or response time was observed, while at higher times the slopes of the electrode started to decrease.
as an anion electrode. It had a life time up to 2 months. An Iron(III) ion-selective based on a μ-bis-(tridentate) ligand (2-phenyl-1,3-bis [3’-aza-4’-(2’-hydroxyphenyl)-prop-4-en-1’-yl]-1,3-imidazolidine) was constructed by Gupta et al. . It had a working pH range 3.5 - 5.5. The age of this electrode was 2 months. Sil et al.  prepared a coated-wire iron (III) ion-selective electrode based on iron complex of 1,4,8,11-tetraazacyclotetradecane. The slope of that electrode was monovalent (60 ± 5 mV/decade), with a pH working range 1.5 - 3.5. A novel ion se- lective potentiometric sensor for direct determination of Fe(III) in the presence of Fe(II) was constructed by Mashhadizadeh et al. . It was based on 2-[(2-hydroxy-1-propenyl-buta-1,3-dienylimino)-methyl]-4-p-tolylazo- phenol as a neutral carrier. It showed a super-Nernstian behavior (28.5 mV/decade) for at least 2 months. It works within pH range 4.5 - 6.5. Mahmoud  applied iron ion-selective electrodes for direct potentiometry and potentiotitrimetry in pharmaceuticals. The electrode was based on ion association complexes of Iron(II) 2,4,6-tri (2-pyridyl)-1,3,5-triazine with tetraphenylborate or phosphotungstic acid. In addition, plasticized carboxylated PVC was applied for this membrane. It worked within a pH range 3.2 - 7.1 and a life time of 3 months. Ribo- nucleic acid as a novel ionophore for potentiometric membrane sensors of some transition metal ions was used by Hassan et al. . It showed a Nernstian behavior toward Fe 2+ (35.5 mV/decade) over a pH range 4.0 - 6.5 (for 10 −6 - 10 −2 M). Ferroin-TPB was applied as a membrane sensor for the potentiometric determination of ei- ther Fe 2+ or Fe 3+ ion by Hassan and Marzouk . This type of sensor was based on responding to the charged ion complex “ferrion”. It behaved like a cationic divalent electrode (30 mV/decade). It showed a pH range 3 - 9 down to 4 × 10 −7 M ferrion.
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An Ag + -selective electrode based on thiaazacrown ether as ionophore with lower detection limit was prepared. The ion flux was decreased by controlling concentration of primary ion in inner solution according to the solubility product constant of AgCl. With the optimal composition of membrane, this electrode has a good Nernst response of 60.0 mV/decate in the linear range of 1.0 × 10 -9 – 1.0 × 10 -5 M with a lower detection limit of 2.9 × 10 -10 M Ag + . The electrode can be used as indicator sensor for the potentiometric titration of mixture solution of Cl - , Br - and I - .
by fission of uranium nuclei is incorporated into the bones. particles emitted by this isotope may produce bone . It may also cause anaemia and oxygen shortages. It is used in a variety of optical materials, paints, plastics, bricks, tiles and ferrite magnets (Baumann, atomic absorption et al., 2001), flame AES (Tarun et al., the determination of strontium. These methods required large infrastructure back up, relatively expensive and time consuming. Thus ion- selective electrodes due to its simple preparation, high selectivity, high sensitivity, wide concentration range and fast response time are the effective analytical device for the determination of strontium in solution (Singh et. al., 2013; et al., 1998; Ganjali, et
The need for the determination of heavy metals increased during the last years because of growing environmental problems 1-3 . Lead is one of the heavy elements, which is almost present in the different industrial waste effluents. Many industries such as lead glasses 4 and optical sensors 5 use lead salts as main components. It is also considered as one of the radionuclides that present in the radioactive waste solution. Accurate determination of lead ions is of great interest since it is sometimes present in very minute concentrations in such matrices. This work is decided to introduce an ion selective electrode (ISE) for accurate and precise quantitative analysis of lead ions.
The coated-graphite electrodes were prepared according to previously reported method [20-22]. Graphite rods (3 mm diameter and 10 mm long) were prepared from spectroscopic grade graphite. A shielded copper wire was glued to one of graphite rod with silver loaded epoxy resin and the rod was inserted into the end of a PVC tube. The working surface of the electrode was polished with a polishing cloth. The electrode was rinsed with water and methanol and allowed to dry. A mixture of PVC, plasticizer, NaTPB and ionophore was added to about (total mass of 100 mg) 2 mL of THF.
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The effect of the test solution pH on the potential response of the sensor was tested in a 1.0×10 −3 mol L -1 Tb (III) solution over the pH range of 2.0-10.0 and the results are shown in Fig. 3 which shows the electrode response to be independent from solution pH in a range of about 2.8–8.5. At pH values <2.8 the potential response increases irregularly most probably due to the response of the electrode to H 3 O + ions in solution through the protonation of nitrogen atoms of PPH. The observed
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In order to assess the reliability of the new quetiapine electrode the real samples previously determined were also measured using high performance liquid chromatographic (HPLC) as independent standard method. In such chromatographic analysis, acetonitrile and phosphate buffer mixture (40:60) was used as the mobile phase. The applied column was RP-C18 (250mm × 4.6mm, 5µm particle size) and the flow rate was 1 mL/min. Prior to the analysis the column was flushed for one hour by mobile phase without sample for washing. The investigated real samples of the pharmaceutical formulations as well as the human urine were measured using HPLC previously calibrated by injection of 20 µL sample.
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The response to the main ions in the solution containing different interfering ions, that is, the selectivity of ion-selective electrode is one of the most important measurement parameters . Selectivity of ISE is quantitatively related to equilibria at the interface between the ion-selective membrane and the sample. Bakker’s separate solution method was used to determine the unbiased selectivity coefficients, K pot Pb,J , after the electrodes were conditioned in 1×10 -3 mol/L NaNO 3 for 12 hr.
Plasticizer plays an important role on optimizing the physical properties of the membrane by reducing the high glass transition temperature of PVC, as well as increas- ing the mobility of the active species and enhancing the flexibility of the polymer chain . Also, it provides a good ionic conductivity under the ambient conditions which allow the diffusion of the membrane components into a homogenous lipophilic environment. Moreover, the nature of plasticizer significantly affected the selec- tivity and measuring range of ISEs . It is known that the addition of proper lipophilic additive to membrane demonstrates a significant improve in the characteristic performance of ion selective electrode such as selectivity, stability and response time. Besides, it reduce the mem- brane impedance . Even though the presence of ion exchangers in the membrane provides beneficial effects, but the excess amount of it declines the electrode perfor- mance .
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With the demand for in situ monitoring and field analysis, gas-diffusion potentiometric method based on an internal glass membrane pH electrode was employed for the detection of TAN [15-17]. However, this method suffers from problems of from volatile amines, poor sensitivity and difficulty in miniaturization [15,18]. Moreover, current pH-based electrodes are mainly used for the determination of TAN in freshwater . Meyerhoff’s group later adopted the polymeric membrane ammonium- selective electrode that possesses attractive features such as simplicity, low cost, and high sensitivity as an internal probe in the design of potentiometric sensors capable of selectively and sensitively sensing ammonia in various samples [15,20-22].
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Schiff base (SSDA) was employed as aluminum selective ionophore in the preparation of aluminum ion-selective electrode. This Schiff base was selected due to its special ring structure, which included two –C=N groups and two –OH groups. Because the lone pair electrons were belonged to both oxygen and nitrogen, a more stable coordination compound could be easily obtained by the coordination between Al 3+ which had empty orbit and Schiff base ionophore which had lone pair electrons. So these two ring-conjugated structures in rich ion situation were expected to improve the electrode response performance. The coordination mechanism of Al 3+ and schiff base ionophore was showed in the Fig.2.
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A sensitive and selective method is required to gain a precise result of lutetium determination. Many techniques have been used for the determination of Lu 3+ ion such as mass spectrometry (MS), X-ray fluorescence spectrometry, inductively couple plasma mass spectrometry (ICP-MS), Isotope dilution mass spectrometry, inductively couple plasma atomic emission spectrometry (ICP-AES), etc. Despite the fact that these methods are precise and sensitive, they are also expensive and time- consuming. Another method for the determination of this element is the ion-selective electrode (ISE) for Lu 3+ potentiometric titration. The ISEs work fast, and they are easily prepared without any special or expensive equipment. There have been only a few reports of Lu 3+ ion- selective electrodes in the literature [3-9].
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All reagents used were of analytical grade. The solutions were prepared using twice distilled water. The pH adjustments were made with dilute sulphuric acid and sodium hydroxide solutions as required. A stock solution of thiocyanate was prepared by dissolving an appropriate amount of potassium thiocyanate in 100 ml of water. Working solutions were prepared by successive dilutions. H 2 SO 4 and NaOH solutions having different concentrations were used to study the pH dependence of thiocyanate-selective electrode.
A fluoride-sensing system, consisting of polymer membrane in which Si-O bond cleavage by triggering fluoride ions results in the formation of a highly fluorescent coumarin. It was reported thatcoumarins are laser dyes with high radiative quantum yields . Polymer membrerane and Coumarin consists of tert-butyldimethylsilyl (TBS) group which was protecting group for the phenols which were found to be more selective to fluoride with less interference from other ions. For detection of fluoride ions through intramolecular energy transfer from conjugated polymers uses Fluorescence resonance energy transfer (FRET).
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The 1,2- bis(salicylidin aminooxy) ethane that was tested as a lead(II) ionophore is shown in (Fig.1). The ionophore was synthesized by condensing 1,2-bis(aminooxy)ethane with salciylaldehyde with using a previously reported method. High molecular weight PVC, Dibuthyle sebacate (DBS), Dibutyle phthalate (DBP), Acetophenone (AP), Benzyle actate (BA) and Tetrahydrofuran (THF),Sodium tetraphenyl borate(NaTPB) were all obtained from Merck, and these substances were used to prepare the PVC membranes. The nitrate salts of the cations we used (all from Merck) were of the highest purity available. Doubly distilled water in a quartz apparatus was used to prepare all the aqueous electrolyte solutions. The typical composition of the PVC-based lead(II)-selective electrodes was 30 mg PVC, 64 mg plasticizer, 4 mg ionophore and 2% additive. The ionophore, plasticizer, additive and PVC were dissolved in the appropriate volume of THF and this was mechanically stirred. All the membrane cocktails were cast in glass rings placed on glass plates for creating the conventional ion-selective electrodes. The solvent from the PVC membrane was allowed to evaporate for at least 24 hours at room temperature (Fig.2). The thickness of the resulting membrane, as measured by a micrometer, was about 0.3mm. The tube was then filled with internal filling solution (1×10 −3 M)Pb(NO 3 ) 2 . The electrode was finally
Plasticizer or solvent mediator mainly acts as a membrane solvent allows a homogeneous dissolution and diffusional mobility of the ion-pair in the membrane [34-40]. Nature of the plasticizer has a noticeable effect on analytical responses e.g. slope, linear domain and selectivity of PVC membrane electrode. Here, three plasticizers with different polarity (dielectric constant) were tested, dibutyl phthalate (DBP with DC of 6.4), nitrobenzene (NB with DC of 35.7) and benzylacetate (BA with DC of about 5.7), as listed in Table 1. The electrode responses showed that membrane had DBP better respond. DBP among the used plasticizers provided an effective linear range and a lower detection limit due to the better extraction of loperamide hydrochloride ions in the organic layer of the membrane. Addition of ionic additive such as sodium tetraphenyl borate (NaTPB) to the membrane composition improved the slope, linear range and the response time. In fact, it helps to the ion-exchange of the lopermide from aqueous solution to organic layer of the membrane. As it can be seen from Table 1, absence of the ion-pair in the membrane causes a very poor response (membrane no. 8), which confirm significance of the ion-pair. The electrodes behavior show that the best Nernstian slope is 57.2±0.4 mV per decade. As a conclusion, membrane no. 4 with the composition of 30% PVC, 5% ion-pair, 1% NaTPB and 654% DBP was the optimum one for the sensor design.
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