Simultaneous determination of cationic surfactants and nonionic surfactants by ion-association titration.

A simultaneous determination of cationic and nonionic surfactants has been developed using ion-association titration. Tetrabromophenolphthalein ethyl ester (TBPE) was used as an indicator. Benzalkonium reacted with TBPE to form a blue ion-associate in the organic phase. When tetrakis(4-fluorophenyl)borate was added dropwise to the solution, the color of the organic phase turned to yellow at the equivalence point. In addition, when a large amount of potassium ion was added to a solution including Triton X-100, Triton X-100 could be determined by the same technique as described above because of formation of the K+-Triton X-100 cation. The proposed method is available for the stepwise determination of cationic and nonionic surfactants in mixtures.     

Potentiometric back-titration of sulfate ion using a tetraphenylborate derivative as a titrant and a titrant-sensitive plasticized poly(vinyl chloride) membrane electrode

A potentiometric back-titration method for the determination of sulfate ions using a plasticized poly(vinyl chloride) membrane electrode without added ion-exchanger is described. A solution of a derivative of tetraphenylborate is used as titrant. The method is based on the ion association between an excess of 2-aminoperimidinium added to the sulfate containing sample and the tetraphenylborate derivative in the titrant. The titration end-point is detected as a sharp potential change due to an increase in the concentration of the free tetraphenylborate derivative at the equivalence point. The sharpness of the titration curve at the end-point is compared for two tetraphenylborate derivatives. Good results are obtained with a solution of sodium tetrakis (4-fluorophenyl) borate.     

Potentiometric back-titration of sulfate ion using a tetraphenylborate derivative as a titrant and a titrant-sensitive plasticized poly(vinyl chloride) membrane electrode

A potentiometric back-titration method for the determination of sulfate ions using a plasticized poly(vinyl chloride) membrane electrode without added ion-exchanger is described. A solution of a derivative of tetraphenylborate is used as titrant. The method is based on the ion association between an excess of 2-aminoperimidinium added to the sulfate containing sample and the tetraphenylborate derivative in the titrant. The titration end-point is detected as a sharp potential change due to an increase in the concentration of the free tetraphenylborate derivative at the equivalence point. The sharpness of the titration curve at the end-point is compared for two tetraphenylborate derivatives. Good results are obtained with a solution of sodium tetrakis (4-fluorophenyl) borate. Received: 9 March 1998 / Revised: 21 April 1998 / Accepted: 25 April 1998     

细胞色素c在微-液/液界面上电化学行为的研究

本文采用电化学技术,研究了细胞色素c（Cyt c）在玻璃微米管尖端处形成的微-水/1,2-二氯乙烷（W/DCE）界面上的电化学行为.选用四丁基铵四苯硼（TBAT-PB）、四丁基铵四氯代苯硼（TBATPBCl）以及四丁基铵四氟代苯硼（TBATPBF）三种不同的有机相支持电解质来研究Cyt c在W/DCE界面上的反应.在电势窗较窄的含TBATPB体系中只能够观察到吸附过程;在电势窗较宽的含TBATPBCl和TBATPBF的体系中,可以同时观察到吸附与离子转移过程.当Cyt c浓度较低时,两种过程都可以观察到;当Cyt c浓度较高时,主要是吸附.文中对这些过程的机理进行了探讨.     

The synthesis and reagent properties of magnesium tetrakis(4-tert.butylphenyl)borate

Magnesium tetrakis(4-tert.butylphenyl)borate, Mg(BAr(4))(2), has been synthesized and screened for its properties as an analytical reagent. Although rather more selective than tetraphenylborate, the compound surprisingly precipitates sodium and proves a good gravimetric reagent for its determination. Quaternary ammonium and trialkylamine ions are precipitated only slowly (in contrast to the rapid precipitation with tetraphenylborate). The new compound exhibits better resistance to proton-initiated decomposition and to free radical attack than the other known tetra-arylborates. The presence of the parent peak, NaBAr(+)(4), in the mass spectrum of the sodium salt is further proof of the remarkable stability. The other tetra-arylborates do not produce parent peaks in the mass spectra of their precipitates.     

Determination of sulfate ion by potentiometric back-titration using sodium tetrakis (4-fluorophenyl) borate as a titrant and a titrant-sensitive electrode

A potentiometric back-titration method for the determination of sulfate ions using a plasticized poly(vinyl chloride) membrane electrode sensitive to a titrant is described. The method is based on ion association between the excess of 2-aminoperimidinium added to the sulfate ion in the sample and sodium tetrakis (4-fluorophenyl) borate (FPB) in the titrant. The titration end-point was detected as a sharp potential change due to an increase in the concentration of the free FPB at the equivalence point. The end-point was detected even in the presence of a 20-fold excess of common cations and anions relative to the concentration of the sulfate ion within approximately 2% of titration error. A linear relationship between the concentration of the sulfate ion and the end-point volume of the titrant exists in the sulfate ion concentration range from 2x10(-4) to 3x10(-3) mol l(-1) using 10(-2) mol l(-1) FPB solutions as the titrant. The present method could be applied to determine sulfate ions in sea water.     

Plastic membrane ion-selective electrode for the determination of denatonium benzoate (Bitrex).

A poly(vinyl chloride) matrix membrane ion-selective electrode for the determination of the denatonium ion based on the denatonium salt of tetraphenylborate is described. The response characteristics of the electrode for the denatonium ion and for several quaternary ammonium compounds were studied. The potentiometric determination of denatonium benzoate in rapeseed oil in the range 1-10 ppm agreed to within +/-5% of the spiked amounts. The application of the electrode to the titrimetric determination of several quaternary ammonium compounds using sodium tetraphenylborate as the titrant is also described.     

Optical Sensing Membrane Based on Tetrabromophenolphthalein Ethyl Ester for the Determination of Cationic Surfactants

Abstract

An optical sensing membrane for detection of cationic surfactants was developed. The optical sensing membrane is 2‐nitrophenyl octyl ether‐plasticized poly(vinyl chloride) membrane incorporating tetrabromophenolphthalein ethyl ester (TBPE). The response of the optical membrane to cationic surfactants was a result of extraction of cationic surfactant into the PVC membrane. The protonated TBPE deprotonates forming an ion associate with the extracted cationic surfactant; simultaneously, the deprotonation of the TBPE is accompanied by a spectral change. Namely, the extracted cationic surfactant changes color of the membrane from yellowish green to blue (absorption maximum: 622 nm). The optical membrane responds to cationic surfactants such as Zephiramine and cetyltrimethylammonium bromide in the concentration range from 1 µM to 100 µM.     

Titanium(IV) chloride and quaternary ammonium salt promoted Baylis-Hillman reaction.

The Baylis-Hillman reaction of aldehydes with alpha,beta-unsaturated ketones can be drastically affected by the reaction temperature and Lewis bases. When the reaction was carried out at -78 degrees C using catalytic amounts of quaternary ammonium salts (R4N+X-, X = Cl, Br, I) as Lewis bases, in the presence of titanium(IV) chloride, the chlorinated aldol adduct 1 was obtained as the major product. Quaternary ammonium bromides and iodides (R4N+X-, X = Br, I) have higher catalytic activity than corresponding chlorides (R4N+Cl-). Quaternary ammonium fluorides (R4N+F-) do not have activity at all. The amounts of Lewis acid and quaternary ammonium salts used affect the reaction rate and product. A plausible reaction mechanism is proposed. If the reaction was carried out at room temperature (about 20 degrees C) in the presence of titanium(IV) chloride and quaternary ammonium salts (R4N+X-, X = Cl, Br, I), the elimination product 3, derived from 1, was formed as the major product.     

Trimethoprim-selective electrodes with molecularly imprinted polymers acting as ionophores and potentiometric transduction on graphite solid-contact

This work proposes a new biomimetic sensor material for trimethoprim. It is prepared by means of radical polymerization, having trimethylolpropane trimethacrylate as cross-linker, benzoyl peroxide as radicalar iniciator, chloroform as porogenic solvent, and methacrylic acid and 2-vinyl pyridine as monomers. Different percentages of sensor in a range between 1 and 6% were studied. Their behavior was compared to that obtained with ion-exchanger quaternary ammonium salt (additive tetrakis(p-chlorophenyl)borate or tetraphenylborate). The effect of an anionic additive in the sensing membrane was also tested.Trimethoprim sensors with 1% of imprinted particles from methacrylic acid monomers showed the best response in terms of slope (59.7 mV/decade) and detection limit (4.01 × 10^− 7 mol/L). These electrodes displayed also a good selectivity towards nickel, manganese aluminium, ammonium, lead, potassium, sodium, iron, chromium, sulfadiazine, alanine, cysteine, tryptophan, valine and glycine. The sensors were not affected by pH changes from 2 to 6. They were successfully applied to the analysis of water from aquaculture.     

Measuring quaternary ammonium cleaning agents with ion selective electrodes

Data for coated-wire, ion selective electrodes (ISEs) are presented for cationic surfactant ions found in common cleaners including benzyldimethyltetradecylammonium, benzyldimethyldodecylammonium, and benzyldimethylhexadecylammonium. The ion exchangers dinonylnaphthalene sulfonic acid, tetraphenyborate, and tetrakis(4-chlorophenyl)borate are examined, showing dinonylnaphthalene sulfonic acid to be the favored species. The ISEs exhibit approximately Nernstian behavior down to the 10⁻⁶ M limit of detection with lifetimes in excess of 50 days when used continuously, and a shelf life of over 100 days. Reaching the upper detection limit at the critical micelle concentration requires use of polymeric-membrane reference electrodes including a new membrane cocktail, which allow response measurements of an order of magnitude higher than the traditional fritted-glass reference electrode. The surfactant ISEs show excellent selectivity over the common metal ions Na⁺, K⁺, Mg²⁺, Ca²⁺, and Cu²⁺ with selectivity coefficients less than 10^−5.3. The ISEs are also selective over the lower molecular weight quaternary ammonium ions tetradecyltrimethylammonium, dodecyltrimethylammonium, benzyldimethyl(2-hydroxyethyl)ammonium, and tetrabutylammonium with selectivity coefficients ranging from 10^−1.7 to 10^−5.5. Use of a single electrode to determine accurately the total cationic surfactant concentration in common cleaning solutions is accomplished with information about concentration dependent interferences and a modified Nikolsky–Eisenman model. Finally, quaternary ammonium surfactants have a deleterious effect on the measurements of pH and common ions like K⁺, Mg²⁺ and Ca²⁺ with polymeric ISEs. This makes it critical to include surfactant electrodes in a detector array when cleaning agents are present.     

Mixed ternary ion associate formation between xanthene dye, cinchona-alkaloid and quaternary ammonium ion and its application to the determination of trace amounts of quaternary ammonium salts in pharmaceuticals

Xanthene dyes such as eosin and tetraiodofluorescein form 1:2 ion associates with quaternary ammonium ions at pH 7-9; however, the development of color in the organic solvent is poor. When a quaternary ammonium salt is added in the extractable 1:2 associate formed between a xanthene dye and a cinchona-alkaloid in the neutral media, a mixed ternary ion associate (xanthene dye:cinchona-alkaloid:quaternary ammonium ion=1:1:1) is formed. Its extractability is enhanced due to the more bulky associate formation. The ion association caused by addition of cinchona-alkaloids is unique. Of the cinchona-alkaloids, quinidine and cinchonidine with tetraiodofluorescein show excellent effects on sensitivity and extractability. Eosin and tetraiodofluorescein are useful as ion association reagents in the ion associate formation. The apparent molar absorptivities are about 1×10⁵ l mol⁻¹ cm⁻¹ and the calibration range for quaternary ammonium salt is from 2.5×10⁻⁷ to 1.5×10⁻⁶ M. The proposed method is applicable to the selective and sensitive determination of cetylpyridinium chloride, berberine chloride and benzethonium chloride in pharmaceuticals.     

DFT investigation of the tri(amino)amine N(NH(2))(3)(2+) and the tri(azido)amine N(N(3))(3)(2+) dications and related mixed amino(azido)ammonium ions (N(3))(x)N(NH(2))(4-x)(+) (x = 0-4)(1)

Structures of the tri(amino)amine N(NH(2))(3)(2+) and the tri(azido)amine N(N(3))(3)(2+) dications were calculated at the density functional theory (DFT) B3LYP/6-311+G level. The tri(amino)amine dication (NH(2))(3)N(2+) (1) was found to be highly resonance stabilized with a high kinetic barrier for deprotonation. The structures of diamino(azido)amine dication (NH(2))(2)N(N(3))(2+) (2), amino(diazido)amine dication (NH(2))N(N(3))(2)(2+) (3), and tri(azido)amine dication (N(3))(3)N(2+) (4) were also found to be highly resonance stabilized. The structures and energetics of the related mixed amino(azido)ammonium ions (N(3))(x)N(NH(2))(4-x)(+) (x = 0-4) were also calculated.     

Potentiometric titration of organic cations precipitated by tetraphenylborate

Summary Sodium tetraphenylborate has been used for the potentiometric precipitation titration of some water-soluble organic cations, mostly those containing a quaternary ammonium group. Emf's were monitored with a fluoroborate ion-selective indicator electrode and a double-junction reference electrode. Other liquid-membrane electrodes, such as the perchlorate and nitrate, also respond to the cations investigated. The solid-state cyanide electrode responds to those cations yielding potentiometric breaks of > 70 mV with the fluoroborate electrode. The following compounds were examined: procaine, diphenhydramine, chlorpheniramine, methylene blue, dimethyl yellow, benzidine, pyridine, acetylmethylcholine, thiamine.This paper was presented at the International Symposium on Electroanalysis in Cardiff, England, on April 13, 1981     

Separation and Concentration of the Trimethylselenonium Ion for Its Determination in Urine by Graphite Furnace Atomic Absorption Spectrometry

The separation and concentration methods for the trimethylselenonium ion (TMSe) in urine samples were developed utilizing the formation of the ion pair of TMSe with tetrakis(4-fluorophenyl)borate. The ion pair could be quantitatively collected by a solvent extraction technique as well as a cellulose nitrate (CN) filter collection technique. The collected TMSe was determined by graphite furnace atomic absorption spectrometry with the addition of palladium as a matrix modifier. In the case of urine analysis for TMSe, the CN filter technique gave better reproducibility than the solvent extraction technique. The detection limit of this method for TMSe was 1 ngSe/ml for 20 ml of urine sample.     

碳酸氢铵和食盐制纯碱工业中间产物的分析

研究了由碳酸氢铵和食盐为原料生产纯碱的中控分析方法。生产过程中，中间产物母液中共存的离子有Na^ 、HCO3^-、CO3^2-、NH4^ 、Cl^-，其中Na^ 采用钠离子选择性电极测定，此文主要研究了其余四种离子的滴定分析法。     

Non-aqueous and two-phase titrimetric assay of isoxsuprine hydrochloride in pharmaceuticals

Based on the nitrogenous base or quaternary ammonium moiety in isoxsuprine hydrochloride (ISX), two highly accurate and selective titrimetric methods are proposed f or the determination of ISX in spiked human urine, injection and tablets. Non-aqueous titration (Method A) involves removal of protonated amine using mercuric acetate for enhanced basic nitrogen prior to titration with perchloric acid in an acetic acid medium using crystal violet as indicator. Two-phase titration (Method B) is based on ion association complex formation between sodium lauryl sulphate (SLS) and protonated amine of ISX at pH 2.5 in aqueous phase, end point being detected by change in dimethyl yellow color in chloroform layer. The methods are applicable over the concentration range 2.0–20.0 mg and 1.0–10.0 mg for method A and method B, respectively. Calculations are based on 1: 1 molar ratio, i.e., JSX: HClO₄ for method A and ISX: SLS for method B, owing to the presence of one nitrogen atom. Method A is applicable to the determination of ISX in tablets whereas method B is applicable to spiked human urine, injection and tablets. The methods are validated statistically by comparing the results with those of the reference method by applying the Student’s t-test and F-test. The accuracy was further ascertained by recovery studies via standard addition technique.     

Primary amine drug selective electrodes with special crown ethers as neutral carriers

Ionophores selectively sensitive to primary amines have been synthesized which display low potentiometric selectivity coefficients for K+, Na+ and NH4+ ions, secondary and tertiary amines as well as quaternary ammonium ions. These ionophores include macrocyclic polyethers with dinaphthyl subunits and azocrown ether with nitrogen donor atoms. The feasibility of these ionophores for preparing primary amine drug selective electrodes was investigated in detail. Practically usable PVC membrane electrodes sensitive to primary amine drugs, such as mexiletine, dopamine, metaraminol and tryptamine, and aliphatic primary amines have been prepared with these ionophores as neutral carriers. Direct potentiometric methods for assaying these drugs have been proposed by using the prepared electrodes. The proposed primary amine drug selective electrodes are remarkably superior to those based on ion-associates. Compared with the electrodes based on common ethers, the interference by K+, Na+ and NH4+ ions is substantially reduced. A digital simulation of the electrochemical process concerning the membrane transport was performed and some interesting conclusions have been drawn.     

Evaluation of eluents in thermospray liquid chromatography-mass spectrometry for identification and determination of pesticides in environmental samples.

The influence of different eluents in positive and negative ion mode thermospray liquid chromatography-mass spectrometry was studied with several groups of pesticides, including carbamates, chlorotriazines, phenylureas, phenoxy acids and organophosphorus and quaternary ammonium compounds, and the corresponding degradation products. Using the positive ion mode in combination with reversed-phase eluents the base peaks generally corresponded either to [M + H]+ for the chlorotriazines and their hydroxy metabolites or to [M + NH4]+ for the carbamates, the phenylureas, the organophosphorus pesticides and their oxygen analogues. In the negative ion mode different processes such as (dissociative) electron-capture and anion attachment mechanisms occurred. Fragment ions such as [M - CONHCH3]- for the carbamates, [M - H]- for the chlorotriazines, phenylureas and chlorinated phenoxy acids and [M].-, [M - R]- (R being a methyl or ethyl group) for organophosphorus pesticides were usually formed. Depending on the eluent additive used (ammonium acetate, ammonium formate and/or chloroacetonitrile), three different adduct ions were formed: [M + CH3COO]-, [M + HCOO]- and [M + Cl]-. Normal-phase eluents with cyclohexane, n-hexane and/or dichloromethane provided more structural information and enhanced the response of several compounds. The positive ion mode was useful for the detection of chlorinated phenoxy acids and chlorophenols which could not be detected in the positive ion mode using reversed-phase systems. The base peaks generally corresponded to [M].+, [M + H]+ or [M - Cl]+. For the characterization of difenzoquat, a quaternary ammonium pesticide of which trace level analysis is troublesome, a post-column ion-pair extraction system was used. An aqueous mobile phase with a sulphonate-type counter ion was applied and an extraction solvent containing cyclohexane-dichloromethane-n-butanol (45:45:10) was used in thermospray liquid chromatography-mass spectrometry. Illustrative examples of the determination of residue levels of pesticides in soil matrices are shown.     

Towards Reversibility of Ion Transfer Across the Interface between Valinomycin Membranes and Aqueous Electrolyte Solutions

Valinomycin-based potassium-selective membranes doped with potassium tetrakis(4-chlorophenyl)borate (KClTPB) or sodium tetrakis(4-fluorophenyl)borate (NaFTPB) are studied in KCl, NaCl, and CaCl₂ solutions by potentiometric and electrochemical impedance methods. Before contact with KCl, membranes doped with NaFTPB provide Nernstian potentiometric response to Na⁺ ions, which is lost after conditioning the membranes in KCl. The membranes doped with KClTPB even before contact with KCl give no Nernstian response to Na⁺ ions. In CaCl₂ solutions, none of the membranes provide a regular potentiometric response. Despite the difference in potentiometric behavior, the impedance spectra of the membranes are very similar in all solutions regardless of prior conditioning of the membranes. No evidence for a hindrance towards charge transfer processes is observed. The results suggest that the membrane/solution interface is reversible for interfering ions as well as for potassium, and the contamination of solutions with the latter is the sole reason for the lack of Nernstian response in the interfering electrolytes.