Enantioanalysis of S-Ketoprofen Using Enantioselective,Potentiometric Membrane Electrodes

Abstract

Maltodextrins with different dextrose equivalent (DE) values (maltodextrin I: DE 4.0–7.0; maltodextrin II: DE 13.0–17.0; maltodextrin III: DE 16.5–19.5) were used for the design of three enantioselective, potentiometric membrane electrodes (EPMEs) for the assay of S-ketoprofen. The linear concentration ranges for the proposed electrodes were 10^?10 to 10^?8, 10^?9 to 10^?5, and 10^?10 to 10^?7 mol/L, with slopes of 58.0, 58.67, and 58.93 mV/decades of concentration and limits of detection of 1.49 × 10^?8, 2.43 × 10^?8, and 4.19 × 10^?11 mol/L for EPMEs based on maltodextrin I, II, and III, respectively. The EPMEs showed high reliability and effectiveness for the enantioanalysis of S-ketoprofen raw material and its pharmaceutical formulations.     

Enantioselective,Potentiometric Membrane Electrodes for the Determination of L‐Pipecolic Acid in Serum

L ‐Pipecolic acid is a marker for peroxisomal disorders. Three enantioselective, potentiometric membrane electrodes were designed for the enantioanalysis of L ‐pipecolic acid. These electrodes are based on carbon paste impregnated with different maltodextrins (DE: 4.0–7.0 (I), 13.0–17.0 (II) and 16.5–19.5 (III), respectively) as chiral selectors and they can be used reliably for enantiopurity assay of L ‐pipecolic acid using a potentiometric method in the concentration ranges of 10^?8–10^?3, 10^?8–10^?5 and 10^?10–10^?6 mol/L for the maltodextrins I, II and III, respectively, based electrodes, with very low detection limits (magnitude orders of 10^?9 for I and II, respectively and 10^?12 mol/L for III). The proposed electrodes can be successfully applied for the enantioanalysis of L ‐pipecolic acid in serum samples.     

Enantioanalysis of L-Histidine Using Enantioselective,Potentiometric Membrane Electrodes Based on Maltodextrins

Three enantioselective, potentiometric electrodes (EPMEs) based on maltodextrins with different values of dextrose equivalent (DE) (maltodextrin I: DE 4.0–7.0; maltodextrin II: DE 13–17; maltodextrin III DE 16.5–19.5) were proposed for the assay of L-histidine in histidine raw materials and from its pharmaceutical formulation. The slopes of the electrodes were 58.3, 58.9, and 58.5 mV/decade of concentration for maltodextrin I, II, and III-based electrodes, respectively, and the detection limits were 1.97 × 10^?12 mol/L, 1.72 × 10^?12 mol/L, and 1.4 × 10^?11 mol/L, respectively. All the electrodes are enantioselective and selective over polyvinylpyrrolidone, creatine, and creatinine. The L-histidine can be determined in the presence of D-histidine with recovery values higher than 99.10%. The proposed electrodes were successfully used for uniformity content tests of L-histidine in food supplements; the average recovery was higher than 97.30%. The surfaces of the electrodes were stable and easily renewable by simply polishing the alumina paper.     

Determination of L‐Vesamicol in Serum Samples Using Enantioselective,Potentiometric Membrane Electrodes Based on Antibiotics

Abstract

Enantioselective, potentiometric membrane electrodes (EPMEs) based on antibiotics are proposed for the enantioanalysis of L‐vesamicol. A carbon paste was modified with antibiotics (vancomycin, teicoplanin, and teicoplanin modified with acetonitrile), as chiral selectors. The EPMEs based on antibiotics were reliably used for enantiopurity tests of L‐vesamicol using the direct potentiometric technique. The following linear concentration ranges: 1.0×10^?6–1.0×10^?4, 1.0×10^?6–1×10^?3 and 1×10^?7?1×10^?2 mol/L; and detection limits: 1.1×10^?7, 9.6×10^?8, and 3.6×10^?8 mol/L were determine for vancomycin, teicoplanin, and teicoplanin modified with acetonitrile–based EPMEs, respectively. The proposed EPMEs were applied for the enantioanalysis of L‐vesamicol in urine samples.     

1‐Pyrrolidine Dicarbodithioate Based Electrodes for Determination of Iron(III) in Lubrication Oil

The lipophillic ammonium salt of 1‐pyrrolidine dicarbodithioic acid (PCDT) (I) was introduced as a new selective ionophore for an iron selective electrode. In addition, the effect of immobilization of 18‐crown‐6 (18CE6) (membrane type‐II), on the electrode performance was discussed. The slope of the PCDT‐based (I) electrode was (20 mV/decade). The linear concentration range was (10^?5–10^?1 M) after one day doping. The detection limit for electrode type‐(II) was (1.3×10^?6 M). For membrane with only 18CE6 (type‐III) the linear range and the detection limit were improved (10^?5–10^?1 M and 3.2×10^?6 M, respectively). The pH‐range was between 5–11 for type‐II, and III electrodes, while it was 7–11 for type‐I electrode. Most of the common cations were tested for the evaluation of the electrode selectivity with correlation to the ionic radii of the tested cations. Among them only Ag⁺ and Pb²⁺ were the real interference for type‐III electrode. Application of using the electrode for the determination of iron in lubrication oil samples was performed with RSD (1.77–2.7%) and (1.01–2.3%) for type‐II and III electrodes, respectively. The corresponding recovery ranges were (93.0–99.9%) and (96.3–100%). The obtained results were compared to those of an atomic absorption spectrophotometric method.     

A Novel Screen-Printed and Carbon Paste Electrodes for Potentiometric Determination of Uranyl(II) Ion in Spiked Water Samples

Four new ion-selective electrodes (ISEs) based on poly-(1-4)-2-amino-2-deoxy-β-D-glucan (chitosan) ionophore were constructed for determination of uranyl ion (UO₂(II)) over wide concentration ranges. The linear concentration range for carbon paste electrodes (CPEs) was 1 × 10^–6–1 × 10^–2 mol/L with a detection limit of 1 × 10^–6 mol/L and that for the screen-printed electrode (SPEs) was 1 × 10^–5–1 × 10^–1 mol/L with a detection limit of 8 × 10^–6 mol/L. The slopes of the calibration graphs were 29.90 ± 0.40 and 29.10 ± 0.60 mV/decade for CPEs with dibutylphthalate (DBP) (electrode I) and o-nitrophenyloctylether (o-NPOE) (electrode II) as plasticizers, respectively. Also, the SPEs showed good potentiometric slopes of 29.70 ± 0.30 and 28.20 ± 1.20 mV/decade with DBP (electrode III) and o-NPOE (electrode IV), respectively. The electrodes showed stable and reproducible potential over a period of 54, 62, 101 and 115 days for electrodes I, II, III, and IV, respectively. The electrodes manifested advantages of low resistance, very fast response and, most importantly, good selectivities relative to a wide variety of other cations except Ce(III) ion which interfere seriously. The results obtained compared well with those obtained using atomic absorption spectrometry.     

Amineptine Plastic Membrane Electrode Based on its Ion Associate with Tetraphenylborate and Phosphomolybdic Acid

New amineptine hydrochloride (Am-Cl) ion-selective electrodes (conventional type) based on amineptinium-tetraphenylborate (I) and amineptinium-phosphomolybdate (II) were prepared. The electrodes exhibited mean slopes of calibration graphs of 57.9?mV and 53.8?mV per decade of (Am-Cl) concentration at 25?°C for electrodes (I) and (II), respectively. The electrodes can be used within the concentration range 3.16×10^?5?10^?2?M (Am-Cl) at a pH range of 2.0–3.9 for both electrodes. The standard electrode potentials were determined at different temperatures and used to calculate the isothermal coefficients of the electrodes, which were 0.00172?V?°C^?1 and 0.00091 V?°C^?1 for (I) and (II) electrodes, respectively. The electrodes showed a very good selectivity for (Am-Cl) with respect to a number of inorganic cations and sugars. The standard addition method is successfully applied to determine (Am-Cl) in pure solutions and in amineptine-containing tablets.     

Fabrication of Potentiometric Sensors for the Selective Determination of Ketoconazole

Abstract

The fabrication and analytical applications of two types of potentiometric sensors for the determination of ketoconazole (KET) are described. The sensors are based on the use of KET-molybdophosphoric acid (MPA) ion pair as electroactive material. The fabricated sensors include both polymer membrane and carbon paste electrodes. Both sensors showed a linear, stable and near Nernstian slope of 57.8 mV/decade and 55.2 mV/decade for PVC membrane and carbon paste sensors respectively over a relatively wide range of KET concentration (1 × 10^?2 ? 5 × 10^?5and 1 × 10^?2 ? 1 × 10^?6). The sensors showed a fast response time of < 30 sec and < 45 sec. A useful pH range of 3–6 was obtained for both types of sensors. A detection limit of 2.96 × 10^?5M was obtained for PVC membrane sensor and 6.91 × 10^?6 M was obtained for carbon paste sensor. The proposed sensors proved to have a good selectivity for KET with respect to a large number of ions. The proposed sensors were successfully applied for the determination of KET in pharmaceutical formulations. The results obtained are in good agreement with the values obtained by the standard method.     

Adsorptive Stripping Voltammetric Determination of Antimony by Using Alizarin Red S

Abstract

A sensitive and selective voltammetric method for determination of antimony(III) using Alizarin Red S (ARS) as complexing agent is described. The method is based on the monitoring the oxidation peak of antimony(III)-ARS complex at ?520 mV in ammonium-ammonia buffer (pH = 7.5). The peak current was measured by scanning the potential from ?700 mV versus Ag/AgClto more positive potentials without accumulation in the presence of 1 × 10^?6 mol L^?1 of ARS. The limit of detection (3 s) and limit of quantification (10 s) of the method were calculated from calibration curve as 1.45 µg L^? and 4.8 µg L^? respectively. The calibration plot for antimony(III) was linear in the range of 4.8–30 µg L^?. The interference of various ions was examined. Serious interference from Al(III), Fe(III), Cu(II), Pb(II), and Zn(II) was eliminated by addition of EDTA to the solution. The method was applied to drinking water samples. The recoveries were in the range 94% – 105%. The results obtained from the developed method were compared with those from the differential-pulse anodic-stripping method and no statistically significant difference was found.     

Etilefrine Plastic Membrane Electrodes Based on Individual and Mixed Ion-exchangers of Etilefrinium Phosphotungstate and Tetraphenylborate.

Abstract

Etilefrine hydrochloride (EfCl) selective PVC membrane electrodes based on Etilefrinium phosphotungstate (I), Etilefrinium tetraphenylborate (II) and a mixture of both (III) were prepared, The electrodes exhibited near Nernstian response over the concentration ranges 5.0 × 10^?6 - 1.0 × 10^?1, 6.3 × 10^?6 - 1.0 × 10^?1 and 6.3 × 10^?5 - 1.0 × 10^?1 M EfCl for electrodes I, II and III, respectively. The working pH ranges of electrodes I, II and III were 10 - 8.0, 10 - 7.5 and 10 - 7.5 and their isothermal coefficients were 0.00150, 0.00088 and 0.00072 V/°C, respectively. The electrodes showed good selectivity to EfCl with respect to many inorganic cations, sugars and amino acids. The standard additions method was used to determine EfCl in pure solutions and in pharmaceutical preparations.     

Highly sensitive and selective solid-contact calcium sensor based on Schiff base of benzil with 3-aminosalycilic acid covalently attached to polyacrylic acid amide for health care

Solid-state potentiometric calcium sensors based on newly synthesized Schiff’s base of 3-aminosalycilic acid with benzil [2-hydroxy-3-(2-oxo-1,2-diphenylethylidene)amino) benzoic acid] ionophore I and with isatin [2-hydroxy-3-(2-oxoindolin-3-ylidene amino)benzoic acid] ionophore II ionophores and their covalently attached to polyacrylamide ionophores III and IV, respectively, were developed. The all-solid-state sensors were constructed by the application of a thin film of polymeric membrane cocktail onto gold electrodes that were pre-coated with the conducting polymer poly (3,4-ethylenedioxy-thiophen) as an ion and electron transducer. More than 40 sensors with membranes containing plasticized PVC or poly(butyl methacrylate-co-dodecyl methacrylate as a plasticizer-free membrane matrix were investigated. The constructed sensors contained various amounts of the different ionophores with and without anionic lipophilic additive. The sensor containing 10% of ionophore III and 3% tetra (p-chlorophenyl) borate in acrylate copolymer exhibited a stable potentiometric response over a wide pH range of 4–9. It possessed a linear concentration range of 6 10^?10 to 1 10^?2 mol L^?1 with a Nernstian slope of 28.5 mV/decade and a limit of detection (LOD) of 2 10^?10 mol L^?1. It exhibited a good selectivity for calcium to other cations. The selectivity coefficients towards different mono-, di- and trivalent cations were determined with the fixed interference method (FIM) and separate solution method (SSM). The sensor’s life time is more than 3 months, without significant deterioration in the slope. The proposed sensors were utilized for the determination of calcium concentration in serum. The results were compared with those obtained from routine clinical laboratory electrolyte analyser. The results reveal that the all-solid-state calcium sensor is promising for the point of care testing.     

Enantioselective,Potentiometric Membrane Electrodes Based on Cyclodextrins for the Assay of L‐ and D‐2‐Hydroxyglutaric Acid

Abstract

Enantioselective, potentiometric membrane electrodes (EPMEs) based on immobilization of β‐, γ‐cyclodextrin (CD) or 2‐hydroxy‐3‐trimethylammoniopropyl‐β‐cyclodextrin (as chloride salt) (β‐CD‐derivative) in carbon paste have been designed. The β‐CD and β‐CD‐derivative‐based electrodes were applied in the 10^?8–10^?6 and 10^?7–10^?5 mol/L concentration ranges for the determination of L‐2‐hydroxyglutaric acid (L‐2‐HGA), whereas γ‐CD‐based electrode was applied for the determination of D‐2‐hydroxyglutaric acid (D‐2‐HGA) in the concentration range 10^?6–10^?4 mol/L. The β‐CD‐based EPME showed the lowest detection limit (1×10^?9 mol/L). The enantioselectivity and selectivity of the proposed electrodes for the assay of L‐2‐HGA and D‐2‐HGA, respectively, were determined over D‐2‐HGA/L‐2‐HGA, creatine, and creatinine. The proposed EPMEs can be applied for the enantioanalysis of 2‐hydroxyglutaric acid in urine samples.     

Salicylate-Selective PVC Membrane Electrodes Based on Tribenzyltin(IV) Phenolates as Neutral Carriers

ABSTRACT

A series of tribenzyltin(IV) phenolates were synthesized and used as anion ionophores for PVC membrane electrodes; these novel electrodes exhibit a linear response towards salicylate and an anti-Hofmeister selectivity pattern with high specificity for salicylate over many common anions. The results show that the behavior of the electrodes is considerably influenced by the structures of the carriers and the experimental conditions. Electrodes based on tribenzyltin(IV) p-nitrophenolate possess the best potentiometnc response characteristics and show a linear log[Sal^?] vs. EMF response over the concentration range 0.1–3.98×10^?6 mol.L^?1 in phosphate buffer solutions of pH 5.38 with a detection limit of 2.51×10^?6 mol.L^?1 and a slope of -57.05 mV per decade. The response mechanism was also investigated by use of a.c. impedance and anion transport across liquid membranes. The electrodes were applied to the determination of salicylate in urine samples with satisfactory results.     

Ion Selective Electrodes Based on Brilliant Green Tetrathiocyanatezincate(II)

Abstract

Liquid state, heterogeneous silicone rubber and carbon paste electrodes based on Brilliant green tetrathiocyanatozincate(II) have been prepared and studied. The liquid state electrode, consisting of a 10^?3 M solution of Brilliant green tetrathiocyanatozincate(II) in o-dichlorobenzene supported on lightly cross-linked natural rubber, was the most satisfactory. This electrode responded rapidly when placed in 10^?4 to 10^?1 M solutions of zinc containing a twenty-fold excess of thiocyanate. The potential concentration slope (-29.5 mV per decade change in concentration) was that 2-expected for response to Zn(SON)₄ ²-. The silicone-rubber and carbon paste electrodes also gave near-Nernstian response, but responded more slowly.     

PPb Level Monitoring of Dy(III) Ions by a Highly Sensitive and Selective Dy(III) Sensor Based on a New Asymmetrical Schiff's Base

Abstract

A Dy(III) ion‐selective membrane sensor has been fabricated from polyvinyl chloride (PVC) matrix membrane containing a new asymmetrical Schiff's base [(E)‐N‐(2‐hydroxybenzylidene)benzohydraide] or BBH as a neutral carrier, sodium tetraphenyl borate (NaTPB) as an anionic excluder and nitrobenzene (NB) as a plasticizing solvent mediator. The membrane sensor displays linear potential response in the concentration range of 1.0×10^?2–1.0×10^?6 M of Dy(III). The electrode exhibits a nice Nernstian slope of 20.1±0.8 mV/decade in the pH range of 3.0–8.0. The sensor has a relatively short response time in whole concentration ranges (<20 s). The detection limit of the proposed sensor is 8.0×10^?7 M (～128 ng/mL), and it can be used over a period of six weeks. The selectivity of the proposed sensor with respect to other cations, (alkali, alkaline earth, transition and heavy metal ions) and especially lanthanid ions, is excellent. The practical utility of the sensor has been demonstrated by using it as an indicator electrode in the potentiometric titration of Dy(III) with EDTA.     

Unsymmetrical Tetradentate Schiff Bases Copper (II) Complex as Neutral Carrier for Thiocyanate‐Selective Electrode

Abstract

Three kinds of transition metal chelates of unsymmetrical tetradentate Schiff base, o‐hydroxybenzophenone‐1,2‐diaminobenzene‐pyrrole‐2‐carbaldehyde(H₂L), were synthesized to prepare anion‐selective electrodes and their anion response characteristics were investigated. The results show that the performances of the electrodes are considerably influenced by the nature of the central metals. The proposed electrode with the Cu(II)‐chelate and cationic additive demonstrated an anti‐Hofmeister selectivity sequence with a good selectivity towards thiocyanate in the following order: Thiocyanate>iodide>salicylate>perchlorate>bromide>nitrite>chloride>acetate>fluoride>nitrate>sulfite>sulfate. The electrode had an excellent linear response to thiocyanate from 3.4×10^?7 to 1.0×10^?1 M in phosphate buffer solution at pH 5.0 with a slope of ?58.7 mV per decade, a detection limit of 1.6×10^?7 M, and a fast response time within 5 s over the entire concentration series. Spectroscopic techniques and AC impedance were used to investigate the response mechanism to thiocyanate of the membrane doped with Cu(II)‐chelate. The preliminary application of the electrode for determination of thiocyanate in wastewater and urine samples is reported.     

A Potentiometric Sensor for Determination of Doxycycline Hydrochloride in Pharmaceutical Preparation and Biological Fluids

This article focused on the construction and characteristics of novelty and sensitivity of modified carbon paste electrodes for determination of doxycycline hydrochloride (DC.HCl) in urine, serum and pharmaceutical preparations. It was based on the incorporation of α-cyclodextrine (α-CD) and multi-walled carbon nanotube (MWCNT) ionophores which improved the characteristics of the electrodes with tricresylphosphate (TCP) (electrode I) and o-nitrophenyloctylether (o-NPOE) (electrode II) as plasticizers, respectively. The constructed electrodes, at optimum paste composition, exhibited good Nernstian response for determination of doxycycline hydrochloride over a linear concentration range from 1.0 × 10^–7 to 1.0 × 10^–2 and 1.22 × 10^–7 to 1.0 × 10^–2 mol L^–1 with detection limit of 1.0 × 10–7 and 1.22 ×10^–7 mol L^–1 and with slope values of (58.7 ± 0.2) mV decade–1 and (58.0 ± 0.6) mV decade–1, for modified carbon paste electrodes (MCPEs; electrodes I and II), respectively. The results showed fast dynamic response time (about 6–7 s) and long lifetime in the range from 4 to 5 months where the response of the electrodes was not affected by pH variation within the range from 2 to 8 and 2 to 7.5 for electrodes I and II, respectively. Electrodes I and II showed high selectivity for doxycycline hydrochloride with respect to a large number of interfering species including foreign inorganic, organic species, excipients and the fillers added to the pharmaceutical preparation. The constructed electrodes were successfully applied for determination of DC.HCl in pure form, its pharmaceutical preparations and biological fluids (urine and serum) using standard addition, calibration curves and potentiometric titration methods. The results obtained using these potentiometric electrodes were comparable with those obtained using official method. The results were satisfactory with excellent percentage recovery comparable or better than those obtained by other routine methods.

     

Lanthanide Recognition: Development of an Asymetric Gadolinium Microsensor Based on N-(2-pyridyl)-N′-(4-nitrophenyl)thiourea

Abstract

The first asymmetric potentiometric Gd(III) microsensor is reported here. N-(2-Pyridyl)-N′-(4-nitrophenyl)thiourea (PyTu₄NO₂) was found to have a very selective and sensitive behavior toward Gd(III) ions, in comparison to other lanthanide ions as well as inner transition and representative metal ions and hence was used as a sensing material in the construction of a Gd(III) microelectrode. The Gd(III) sensor exhibits a Nernstian slope of 17.46 ± 0.3 mV per decade over the concentration range of 1.0 × 10^?8 to 1.0 × 10^?3 M and a detection limit of 3.0 × 10^?9 M of Gd(III) ions. The potentiometric response of the sensor is independent of the solution pH in the range of 4.0–9.0. It manifests advantages of low detection limit and fast response time (10–15 s).     

Application of Novel Praseodymium (III) PVC‐Membrane Electrode for Determination of Pr(III) Ions in Soil and Sediment Samples

Abstract

A novel Pr(III) ion‐selective polyvinyl chloride (PVC) membrane sensor, based on N,N‐bis(α‐methylsalicylidene)diethylenetriamine (BMT) as a new ionophore, has been prepared and studied. The electrode showed good selectivity for Pr(III) ion with respect to most common cations, including alkali, alkaline earth, transition, and heavy metal ions. This electrode has a wide linear dynamic range from 1.0×10^?6 to 1.0×10^?2 M with a Nernstian slope of 19.8±0.2 mV per decade and a low detection limit of 6.5×10^?7 M, in the pH range of 3.0–8.4, while response time was rapid (<15 s). As far as applications of the recommended sensor are concerned, first it was employed as an indicator electrode in the potentiometric titration of Pr(III) ions with EDTA. Second, it was effectively applied to the determination of concentration of Pr(III) ions in soil and sediment samples, and validation with CRMs.     

Thiocyanate-Selective PVC Membrane Electrode Based on Copper and Nickel Complexes of Para-tolualdehydesemicarbazone as Carrier

Abstract

Copper(Cu) and nickel(Ni) complexes of para-tolualdehydesemicarbazone (pTSC) were used as carrier for an thiocyanate ion–selective electrode. The Ni(II)pTSC demonstrated higher selectivity for thiocyanate ions with better performance than Cu(II)pTSC as carrier. The electrode shows a Nernstian slope of 58.8 ± 0.3 mV decade^?1 with improved linear range of 1 × 10^?2 to 1 × 10^?7 M and a low detection limit of 1.25 × 10^?7 M in the pH range of 3–10, giving a relatively fast response and reversibility within 10 s. The selectivity coefficient was calculated using matched potential method. The electrode worked well for nearly 3 months. The response mechanism is discussed by UV-visible spectroscopic technique. The electrodes were used in potentiometric titration of thiocyanate with silver nitrate. Further, the electrode was successfully applied to determine the thiocyanate content in physiological fluids.