Higher Quaternary Ammonium Salts Research Articles

Anion-Exchange Extraction of Doubly Charged Anions by Higher Quaternary Ammonium Salts with Different Steric Accessibility of the Exchange Center

An increase in the steric accessibility of a quaternary ammonium salt (QAS) exchange center leads to a significant increase in the exchange constant for most of the studied doubly charged anions (sulfate, sulfite, molybdate, tungstate, hydrogen phosphate, and selenate), which reaches for “pure” anion-exchange systems of more than five orders of magnitude. The effect of minimizing of an anion-exchange affinity was detected when a solvating additive, heptyl p-trifluoroacetylbenzoate, was introduced into the organic phase. The effect of steric accessibility is not entirely lost due to the conservation of charge of the solvate. The introduction of a solvating additive improves the affinity of anions for the QAS phase significantly (up to 6.5 orders of magnitude). The effect of anion size on the effect of steric accessibility of the exchange center was found for sulfate, sulfite, and thiosulfate ions. An inverse relationship was found for the tetrathionate ion; that is, with a decrease in steric accessibility of the QAS exchange center, anion-exchange extraction is weakened due to the large size of the $${{{\text{S}}}_{{\text{4}}}}{\text{O}}_{6}^{{2-}}$$ ion.

Selenate-selective electrode based on higher quaternary ammonium salts with sterically available exchange center

Selenate-selective electrode based on higher quaternary ammonium salts with sterically available exchange center

Influence of plasticizer nature on the analytical characteristics of ion-selective electrodes based on higher quaternary ammonium salts reversible to doubly charged inorganic anions

It has been established that membranes of carbonate and hydrogen phosphate selective electrodes based on higher quaternary ammonium salts are preferable to be plasticized with o-nitrophenyldecyl ether, membranes of sulfate, selenate, selenite-selective electrodes with 1-bromonaphthalene, sulfite, molybdate, tungstate-selective electrodes with dibutylphthalate. The use of an optimum plasticizer allows, in general, reducing both the lower detection limit of electrodes and the values of selectivity coefficients by about 1 order (depending on the interfering ion). A qualitative explanation is given to the results obtained from the Fouoss theory and the Born model.

Higher Quaternary Ammonium Salts with a Sterically Hindered Exchange Center: Application to the Development of Ion Selective Electrodes Reversible to Metal Thiocyanate Complexes

Ion-selective electrodes based on a sterically hindered higher quaternary ammonium salt, 3,4,5-trisdodecyloxybenzyltrioctadecylammonium bromide, and a plasticizer, 1-bromonaphthalene, reversible to zinc and cobalt thiocyanate complexes, are developed. They are characterized by high analytical performance. The selective determination of zinc and cobalt on their simultaneous presence is achieved by varying the concentration of ligands (thiocyanate ions) in the supporting electrolyte. The mechanism of the coordination of thiocyanate ions with some d-metal cations was studied by IR spectroscopy. It is shown that zinc and cobalt coordinate SCN– ions by the isothiocyanate type, because of which $${\text{Zn(NCS}})_{4}^{{2 - }}$$ and $${\text{Co(NCS)}}_{{\text{4}}}^{{{\text{2}} - }}$$ ions have a high anion-exchange affinity to the membrane phase. The developed electrodes were used to determine zinc and cobalt in cheese, potatoes, and beets.

New Selenite Selective Electrodes Based on Higher Quaternary Ammonium Salts

A new film selenite selective electrode has been developed, with the following membrane composition: (3,4,5-tris-dodecyloxybenzyl)dioxyethyl trimethyl ammonium chloride (5% w/w) as an electroactive component, (poly)vinyl chlorid (33% w/w) as a membrane matrix, 1-bromonaphtalene (42% w/w) as a plasticizer, 4-trifluoroacetylbenzoic acid heptyl ester (20% w/w) as a solvating additive. The electrode has a wide activity range - 7.5×10–7- 10–2 Ì Na2SeO3; slope 29.0±0.4 mV decade–1; detection limit 4×10–7 M Na2SeO3; working pH range 8.6 - 9.7; the potential drift 1.3 mV h–1; the response time 25 s; lifetime up to 3 weeks without observing any deviation, and is selective to selenite ions in presence of chloride, bromide, sulfate and selenate ions.

Carbonate-Selective Electrodes Based on Higher Quaternary Ammonium Salts with Increased Steric Accessibility of the Exchange Site

A film polyvinyl chloride (33 wt %) carbonate-selective electrode based on a higher quaternary ammonium salt with increased steric accessibility of the exchange site, 3,4,5-tris(dodecyloxy)benzyl( oxyethyl)3trimethylammonium chloride (5 wt %), was developed using o-nitrophenyl decyl ether (52 wt %) as a plasticizer and heptyl p-trifluoroacetylbenzoate (10 wt %) as a solvating agent. The limit of detection of hydrocarbonate was 1.9 × 10−9 M, lifetime was 2.5 months, and the slope of the electrode function was 32.3 ± 0.6 mV/decade. The electrode is selective in the presence of interfering SO42-, Cl−, C2O42-, Br−, HPO42-, and NO3- ions, which allows its application for the determination of HCO3- ions in mineral water.

A New Molybdate-selective electrode based on Higher quaternary Ammonium Salts

A New Molybdate-selective electrode based on Higher quaternary Ammonium Salts

Higher quaternary ammonium salts with the sterically accessible exchange center: application for development of Selenate selective electrodes

Higher quaternary ammonium salts with the sterically accessible exchange center: application for development of Selenate selective electrodes

Hydration of p-trifluoroacetyl benzoic acid heptyl ester: how it affects analytical characteristics of sulfate selective electrodes based on higher quaternary ammonium salts

Potentiometric studies of p-trifluoroacetyl benzoic acid heptyl ester (TFABAHE) and its hydrate in sulfate-selective electrodes based on higher quaternary ammonium salts (QAS) have shown that analytical characteristics of the electrodes deteriorate after 2 weeks. This process corresponds in time with accumulations of TFABAHE hydrate form in the membranes, that is confirmed by IR spectroscopy, thermal analysis, electron microscopy and NMR 1H spectroscopy data. It indicates that the solvation of sulfate ions with TFABAHE is performed most likely by the trifluoroacetyl carbonyl group carbon atom. The procedures for determination of sulfate ions in mineral water have been proposed.

Influence of the QAS Nature and Size of a Doubly Charged Hydrophilic Inorganic iIons on the Analytical Characteristics of S4O62−, SO42−, SO32−, S2−, S2O32− Selective Electrodes

The effect of higher quaternary ammonium salts’ (QAS) exchange center steric accessibility and doubly charged hydrophilic inorganic ions size on the analytical characteristics of S4O62−, SO42−, SO32−, S2−, S2O32− ion selective electrodes (ISEs) was studied. It has been established that for SO42−, SO32−, S2−, S2O32− - SE with the improvement of the exchange center steric accessibility in the series TNODA - TB - TE - TM - BHPBTM - (oxyethyl)2TM - (oxyethyl)3TM - (oxyethyl)4TM the selectivity coefficients lgKPot (i, j) decrease significantly. The LDL reducing magnitude and selectivity improvement depends from doubly charged anion size and decreases in series S2− -SO32−-SO42− -S2O32− ions. The maximum effects are achieved for the smallest S2− ion. For S4O62− -SE an inverse relationship is found, i.e. as the steric availability decrease in the QAS series (oxyethyl)4TM -(oxyethyl)3TM - (oxyethyl)2TM - BHPBTM - TM - TE - TB - TNODA - TOD a certain improvement in analytical characteristics is observed.

Application of Zn(NCS) 4 2- and Co(NCS) 4 2- -selective electrodes to the analysis of natural objects and foods

Concentrations of zinc and cobalt in beer, mineral water, beets, cheese, potatoes, and soil are determined by potentiometry, using film Zn(NCS)42- and Co(NCS)42--selective electrodes based on higher quaternary ammonium salts. The developed electrodes enable the determination of zinc and cobalt in concentrations lower than their maximum permissible concentrations (MPCs). The procedures do not require complex or long sample preparation or expensive equipment. The results agree well with the data of atomic emission spectrometry and atomic absorption spectrometry.

An oxalate-selective electrode and its application to analysis

It is shown that the improvement of the steric accessibility of exchange centers of higher quaternary ammonium salts by replacing three long-chain radicals (octadecyl) with three methyl radicals and the addition of a neutral carrier, p-trifluoroacetylbenzoic acid heptyl ester, significantly enhance the selectivity of an oxalate-selective electrode and lower the detection limit. An electrode reversible to oxalate ions is proposed. A procedure is developed for determining oxalate ions in green and black tea.

Zn(NCS)4]2−-Selective electrodes based on higher quaternary ammonium salts (QAS)

We have studied analytical parameters of tetrarhodanozincate-selective film electrodes based on high-lipophilic quaternary ammonium salts: trinonyloctadecylammonium iodide, R-trioctadecylammonium bromide, R-trimethylammonium nitrate, R-tricetylammonium bromide, R-triethylammonium bromide, R-tributylammonium bromide, R-trilaurylammonium bromide, where R is 3,4,5-tris(dodecyloxy)benzyl. A procedure has been developed for the study of the molecular extraction of zinc rhodanide with membrane plasticizers. The applicability of these electrode to zinc determination in solid wastes has been demonstrated.

Using a Zn(NCS) 4 2− selective electrode for determining rhodanide

The occurrence of a ligand, i.e., rhodanide, function of a zinc rhodanide electrode based on higher quaternary ammonium salts is explained by the exchange displacement of zinc rhodanide by free rhodanide from the membrane to the electrode layer of the solution. The limit of its applicability is limited by the dissociation of the quaternary ammonium salt as an associate with Zn(NCS)42− ions. The potency of the electrode in the determination of rhodanide in process solutions of polyacrylonitrile fiber production is shown.

Calculation of equilibrium in anion-exchange extractive systems

Anion-exchange extractive systems based on solutions of higher quaternary ammonium salts in the presence of solvating additives, derivatives of trifluoroacetophenone, were considered. A mathematical model of the extractive system was developed and average solvation numbers and constants of solvation of ClO4−, SCN−, Br−, and NO3− ions by variously structured derivatives of trifluoroacetophenone were calculated from experimental data.

Anion-exchange extraction of zine rodanide complexes by structurally different quaternary ammonium salts

Anion-exchange extraction constants have been determined for the extraction of zine rodanide complexes from neutral solutions by higher quaternary ammonium salts (QASs) of asymmetric geometry containing different numbers of methyl radicals in their cations. The extraction power of toluene solutions of ultralipophilic QASs with respect to zinc rodanide complexes is lower than that of QASs with long hydrocarbon radicals. These results are interpreted in terms of steric hindrances to the association of QAS with zinc rodanide complexes created by the large size of the Zn(SCN)42− anion.