New Ion-Selective Electrodes for Determination of Bupivacaine and Oxybuprocaine

Abstract

PVC membrane electrodes selective for hydrochlorides of the anaesthetics bupivacaine (BpC) and oxybuprocaine (ObC) are prepared. The electrodes have a near Nernstian slope (58 mV for BpC and 51 mV for ObC electrodes) over the range of 1.6 × 10^?5-10^?1M and 1.3 × 10^?1M for BpC and ObC electrodes, respectively. The change in pH of the test solution within the ranges 2.5–6.0 and 3.0–7.4 does not affect the EpC-and ObC-electrodes, respectively. The electrodes have very long life times (10 days for BpC, and 3 months for ObC) and exhibit good seletivity for the investigated compounds with respect to a large number of inorganic cations and organic substances of biological importance. The isothermal coefficients of the electrodes are calculated from the standard electrode potentials at different temperatures. BpC and ObC are determined successfully in some pharmaceutical preparations using the calibration graph technique and potentiometric titration.     

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.     

Construction and analytical applications of liquid-membrane electrodes for atropine and novatropine

Liquid-membrane electrodes sensitive to atropinium and novatropinium cations are described. The atropinium electrode exhibits rapid and near-Nernstian response in the 10^-2–3 × 10^-5 M range over the pH range 2–8.5; the novatropinium electrode shows near-Nernstian response in the 10^-2–3 × 10^-6 M range at pH 2–10. Other alkaloids interfere. Direct potentiometry and potentiometric titrations are used to determine atropine and novatropine in pharmaceutical preparations with satisfactory results.     

Bis (trans-cinnamaldehyde) ethylene diimine dibromonickel (II) complex as a neutral carrier for salicylate-selective liquid membrane and coated graphite sensors

A salicylate PVC-based membrane (SPME) and a coated graphite membrane (SCGE) electrodes by using a new tetracoordinate organonickel complex as ion carrier were prepared. Both sensors show a Nernstian response to salicylate ions over a very wide concentration ranges (1.0×10⁻⁵-1.0×10⁻¹ M for SPME and 1.0×10⁻⁶-1.0×10⁻² M for SCGE) in the pH of 7.0. The best selectivities were obtained for the membrane incorporating 30% PVC, 63% plasticizer, 2% cationic additive and 5% ionophore. The electrodes possess satisfactory reproducibility, very short response time (∼10 s) in the whole concentration ranges, and excellent discriminating ability for salicylate ions with respect to the most common organic and inorganic anions. The detection limits of proposed sensors are 5.0×10⁻⁶ and 7.0×10⁻⁷ M for SPME and SCGE, respectively. The electrodes were successfully used for determination of salicylate in biological samples.     

Polymeric membrane and coated graphite samarium(III)-selective electrodes based on isopropyl 2-[(isopropoxycarbothioyl)disulfanyl]ethanethioate

New polymeric membrane (PME) and coated graphite (CGE) samarium(III)-selective electrodes were prepared based on isopropyl 2-[(isopropoxycarbothioyl) disulfanyl]ethanethioate as a suitable neutral ionophore. The electrodes exhibit Nernstian slopes for Sm³⁺ ions over wide concentration ranges (1.0×10⁻⁵ to 1.0×10⁻¹ M for PME and 1.0×10⁻⁶ to 1.0×10⁻¹ M for CGE). The PME and CGE have limits of detection of 3.1×10⁻⁶ and 5.0×10⁻⁷ M, respectively, and response times of about 20 s. The potentiometric responses are independent of the pH of the test solution in the pH range 4.0-7.0. The proposed electrodes revealed good selectivities over a wide variety of other cations including alkali, alkaline earth, transition and heavy metal ions. The electrodes were successfully applied to the recovery of Sm³⁺ ion from tap water samples and also, as an indicator electrode, in potentiometric titration of samarium(III) ions.     

Novel Ag ion-selective electrodes based on two new mixed azathioether crowns containing a 1,10-phenanthroline sub-unit

Novel polymeric membrane (PME) and coated graphite (CGE) silver-selective electrodes based on two recently synthesized mixed azathioether crowns containing a 1,10-phenanthroline sub-unit were prepared. The electrodes reveal a Nernstian behavior over quite wide Ag⁺ ion concentration ranges with a very low limits of detection (LOD) (i.e. down to 1.0×10⁻⁸ M for CGEs and 8.0×10⁻⁷ M for PMEs). The potentiometric responses are independent of the pH of the test solution in the pH range 3.0-7.0. The electrodes possess advantages of low resistance, very fast response time, relatively long lifetimes and, especially, good selectivities relative to a wide variety of other cations. The electrodes were used, as indicator electrodes, in the potentiometric titration of silver ion and in the determination of Ag⁺ in waste water, photographic emulsion and radiographic and photographic films.     

Highly Selective Chromium(III) PVC‐Membrane Electrodes Based on Some Recently Synthesized Schiff's Bases

Three recently synthesized Schiff's bases were studied to characterize their ability as Cr³⁺ ion carrier in PVC‐membrane electrodes. The polymeric membrane (PME) and coated glassy carbon (CGCE) electrodes based on 2‐hydroxybenzaldehyde‐O,O′‐(1,2‐dioxetane‐1,2‐diyl) oxime (L1) exhibited Nernstian responses for Cr³⁺ ion over wide concentration ranges (1.5×10^?6–8.0×10^?3 M for PME and 4.0×10^?7–3.0×10^?3 M for CGCE) and very low limits of detection (1.0×10^?6 M for PME and 2.0×10^?7 M for CGCE). The proposed potentiometric sensors manifest advantages of relatively fast response and, most importantly, good selectivities relative to a wide variety of other cations. The selectivity behavior of the proposed Cr³⁺ ion‐selective electrodes revealed a considerable improvement compared to the best previously PVC‐membrane electrodes for chromium(III) ion. The potentiometric responses of the electrodes are independent of pH of the test solution in the pH range 3.0–6.0. The electrodes were successfully applied to determine chromium(III) in water samples.     

The calibration and response of ion-selective electrodes at low concentrations of primary ions

Electrolytic generation of ions is proposed for the preparation of standard solutions for the calibration of iodide and silver ion-selective electrodes in the concentration range 10^-4–10^-7 M. The responses of these electrodes and also the copper(II) ion-selective electrode were examined in various electrolyte solutions. The current efficiencies of the electrolytic generation of the iodide ions into the various solutions were measured coulometrically. The advantages of this newly proposed calibration technique are discussed.     

Potassium ion-selective membrane electrodes based on naphtho-15-crown-5

The potassium-selective PVC membrane electrodes based on naphtho-15-crown-5 have rapid, stable and Nernstian response in the range 10^-1–10^-5 M. The selectivity coefficient for potassium over sodium is 4 × 10^-4.     

A calcium-sensitive microelectrode suitable for intracellular measurement of calcium(II) activity

A calcium-selective microelectrode with a l-μm diameter tip suitable for impaling single neurons has been developed. The electroactive material is di[p-(1,1,3,3-tetramethyl-butyl) phenyl] phosphoric acid (t-HDOPP). The selectivity coefficients are about 5 · 10^-7 for k_Ca,K, 1–4·10^-7 for k_Ca,Na, and 10^-3 for k_Ca,Mg. Values reported previously for other calcium-selective electrodes based on long-chain phenylphosphoric acids are given for comparison. The calcium-selective microelectrodes have a linear response in 0.2 M KCl solutions over the range 10^-2–10^-XXX M CaCl₂; 10^-7 and 10^-8 M CaCl₂ solutions containing 0.2 M KCl can be detected but the response is not linear.     

Liquid and poly (vinyl chloride) matrix membrane electrodes for the selective determination of cocaine in illicit powders

The construction of liquid membrane and PVC matrix-type cocainium ion selective electrodes and their use for direct potentiometry and potentiometric titration of cocaine are described. The ion-pair complexes of cocaine cation with reineckate and tetraphenylborate anions are either dissolved in nitrobenzene solvent or dispersed in a PVC matrix, with DOP or DBS plasticizer, and used as the ion-exchange membranes. The electrochemical response characteristics of electrodes incorporating these types of membranes are evaluated with regard to the effect of pH, foreign basic compounds, temperature and gamma-radiation. The electrodes display a stable fast Nernstian response for 10(-2)-10(-5)M cocainium cation over the pH range 3-7, the lower limit of detection being 1 mug/ml. Determination of as low as 20 mug/ml cocaine hydrochloride shows an average recovery of 98% and a mean standard deviation of +/-0.6%. The electrodes exhibit useful analytical characteristics for determining cocaine in some illicit powders. The results agree fairly well with those obtained by gas-liquid chromatography.     

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.     

Liquid membrane electrodes based on quaternary ammonium tetrakis(m-trifluoromethylphenyl)borates

Electrodes based on the appropriate salts give linear responses for 10^-1–10^-4 M tetramethylammonium and tetraethylammonium ions, with some selectivity against alkali metal ions. Use as indicator electrodes in titrations with tetraphenylborate solutions is outlined.     

Comparative chemical ionization mass spectra of tricyclic antidepressant amines and related compounds

Positive-ion methane chemical ionization (CI) mass spectra were obtained for seven underivatized tricyclic amines: amitriptyline, nortriptyline, protriptyline, imipramine, desipramine, cyclobenzaprine and cyproheptadine. Some discrepancies in previously reported spectra were noted. Spectra of protriptyline, cyclobenzaprine and cyproheptadine are reported for the first time. Comparisons are made among the CI spectra and with electron ionization spectra, and relative abundances of major CI ions among the seven compounds are rationalized in terms of substituent and geometric effects. In most cases low-mass iminium ions from anion abstraction were more abundant than [MH]⁺. Hydride abstraction and adduct formation with reagent-gas ions were important. The three heterocyclic amines gave abundant [M]⁺˙ by electron transfer. Protonation at the nitrogen atom on the side chain followed by amine elimination gave tricyclic aromatic fragment ions.     

δ13C, δ15N and δ2H isotope ratio mass spectrometry of ephedrine and pseudoephedrine: application to methylamphetamine profiling

Conventional chemical profiling of methylamphetamine has been used for many years to determine the synthetic route employed and where possible to identify the precursor chemicals used. In this study stable isotope ratio analysis was investigated as a means of determining the origin of the methylamphetamine precursors, ephedrine and pseudoephedrine. Ephedrine and pseudoephedrine may be prepared industrially by several routes. Results are presented for the stable isotope ratios of carbon (δ¹³C), nitrogen (δ¹⁵N) and hydrogen (δ²H) measured in methylamphetamine samples synthesized from ephedrine and pseudoephedrine of known provenance. It is clear from the results that measurement of the δ¹³C, δ¹⁵N and δ²H stable isotope ratios by elemental analyzer/thermal conversion isotope ratio mass spectrometry (EA/TC‐IRMS) in high‐purity methylamphetamine samples will allow determination of the synthetic source of the ephedrine or pseudoephedrine precursor as being either of a natural, semi‐synthetic, or fully synthetic origin. Copyright © 2009 Commonwealth of Australia. Published by John Wiley & Sons, Ltd.     

1,3,4-Trisubstituted-2-azetidinone Derivatives as Novel Receptors for Bismuth(III) Ion-Selective Electrodes: Application in Pharmaceutical and Glass Samples

Abstract

Polymeric membrane electrodes (PMEs) and coated graphite electrodes (CGEs) containing 1,3,4-trisubstituted-2-azetidinone derivatives as ion carriers are reported here for bismuth(III) ion selectivity. These electrodes exhibited Nernstian response for Bi³⁺ ions over a wide concentration range (5.0 × 10^?7 M to 1.0 × 10^?1 M for CGE) with a lower detection limit of 3.98 × 10^?7 M (for CGE) and wide pH range (1.3–5.0). Compared to polymeric membrane electrode, the coated graphite electrode has shown better selectivity for Bi³⁺ ions with respect to common metal ions. Proposed electrodes have been used for the estimation of Bi³⁺ ions in pharmaceutical and glass samples.     

Determination of micromolar concentrations of cyanide in solution with a piezoelectric detector

The silver plated electrodes of a piezoelectric quartz crystal are partly dissolved by cyanide in pH 9.6 solution during a 15-min immersion. The resulting frequency change of the crystal, measured in air, is proportional to cyanide concentration over the range 10^-7–10^-5 M.     

New cocaine-selective membrane electrode

The sensitivity and selectivity of a cocaine-selective membrane electrode have been improved with the use of sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate as an ion-exchanger and tetrakis(2-ethylhexyl) pyromellitate (TEHPY) as a solvent mediator. The use of TEHPY suppressed the responses to lipophilic quaternary ammonium ions and strengthened the response to cocaine. The electrode exhibited a near-Nernstian response over a concentration range of 10⁻²to 10⁻⁶ M cocaine with a slope of 56 mV per decade. The lower limit of detection was 4 × 10⁻⁷ M cocaine. Interference by other drugs (morphine and codeine) and a stimulant (methamphetamine) was negligible. This electrode was applied for the determination of cocaine in a drug mixture containing cocaine and morphine, which is widely used to suppress acute pain in cancer patients. The concentration of cocaine, different in each patient, was measured precisely with an average recovery of 99.9% and a mean relative standard deviation of 0.56%.     

Ion-selective electrodes based on tetraphenyl-phosphonium 12-tungstosilicate and on crystal violet tetraphenylborate in the potentiometric titration of acid and basic dyes

Poly(vinyl chloride) membrane electrodes containing the specified substances are suitable as indicator electrodes in titrations of basic dyes with sodium tetraphenylborate solution and of acidic dyes with crystal violet solution. Useful curves are obtained even at the 10^-3 M level.     

Bisquaternary-drug membrane electrodes with high sensitivity

The construction and performance characteristics of ion-selective plastic membrane electrodes for succinylcholine, hexamethonium and decamethonium are described. The electrodes, based on ion-pair complexes with triphenylstillbenyl borate (TPSB), show near-Nernatian responses over the range 10^?2–10^?6 M or less, with very low limits of detection at around 10^?7 M. The responses are not affected by pH in the range 2–10. The selectivity relative to some inorganic ions, amino acids, neurotransmitters, drugs and various drug excipients is reported.