Photometric determination of quaternary ammonium compounds with hexanitrodiphenylamine. I.

Dissociation contants, partition coefficients and absorption spectra have been determined for hexanitrodiphenylamine and pentanitrodiphenylamine. The two compounds have quite different dissociation constants and can be easily separated. Both substances give compounds with quater- nary ammonium ions which can be extracted with chloroform or methylene chloride from an aqueous solution. to obtain a pure hexanitrodiphenylamine compound the reagent must be free from pentadinitrodiphenylamine and the extraction made at high pH.     

Inclusion of quaternary ammonium compounds by calixarenes

In weakly polar solvents, strong association occurs between calixarene anions and tetraalkylammonium cations, with the magnitude of the observed equilibrium constants depending upon the charge on the anion, the solvent, the ring size of the calixarene and the nature of the alkyl group of the cation. Large upfield shifts of the methyl resonances of the [(CH₃)₄N]⁺ cation in solutions of [(CH₃)₄N]₂[p-t-butylcalix[6]arene-2H] indicate cation inclusion in a structure which is possibly identical with that found for the solid salt by X-ray crystallography. This shows one of the cations to be included within a partial cone structure of a hinged 3-up, 3-down conformation of the calixarene. The functionalised tetramethylammonium ions, choline and acetyl choline, are also strongly included by various calixarene anions but attempts to detect significant modification of the reactivity of acetyl choline resulting from inclusion have not been successful.This paper is dedicated to the commemorative issue on the 50th anniversary of calixarenes.     

Photometric determination of tellurium with bismuthiol II

A method for the photometric determination of tellurium based on the extraction of the yellow-coloured complex of tellurium with bismuthiol II is presented. The described method permits the determination of as little as 0.01 % of tellurium in ores directly without preliminary separation. After the isolation of the element by reduction with tin^II chloride even smaller amounts can be determined.     

The adsorption of quaternary ammonium salts at a mercury solution interface: Part II. Non-symmetrical quaternary ammonium salts

The adsorption of triethyl alkyl (and allyl) ammonium bromides on a mercury electrode has been investigated. The isotherms and values of the free energy of adsorption yield information on the mode of adsorption of the cations. The formation of partial bimolecular films on the surface of mercury by the cations studied has been described and a simple explanation put forward concerning the mechanism of destruction of these films.     

A rapid method of separation and determination of quaternary ammonium compounds involved in carnitine metabolism

The rapid separation of several quaternary ammonium compounds involved in carnitine metabolism is reported. Two convenient methods based on spectrophotometry and liquid scintillation counting are employed to determine the eluting compounds. The application of the techniques to biological determinations is discussed.     

烯胺型四氢异喹啉季铵碱化合物的合成

1位酯基取代、氮上烷基取代的四氢异喹啉在与碘甲烷成盐后不发生通常的Stevens重排反应,而是酯基α位烯醇化后发生氧烷基化反应,生成了稳定的烯胺型四氢异喹啉季铵碱化合物,收率在90％以上,该类化合物为首次报道.     

Spectrophotometric determination of aluminium with ferron and a quaternary ammonium salt

The reproducibility of the ferron method for aluminium has been greatly improved by the addition of cetyltrimethylammonium chloride (CTMAC). The improvement is attributed to reduction of the reagent blank and increased stability of Al(ferron)(3-)(3). The aluminium-ferron complex formed in the presence of CTMAC has an absorption peak at 385 nm. The interference from iron can be eliminated by application of a correction based on measurement at two wavelengths.     

Quantitation of quaternary ammonium compounds using electrospray mass spectrometry

A sensitive and specific electrospray mass spectroscopic assay has been developed for the quantitation of the series of quaternary ammonium surfactant compounds dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, and octadecyltrimethylammonium bromide and neostigmine bromide. Standard solutions were prepared in methanol, with an appropriate quaternary ammonium internal standard used in each case, and injected into a carrier solvent comprising acetonitrile (99%) and methanol (1%). Detection was based upon the positively charged quaternary ammonium ion in each case. Using this new technique, significant increases in sensitivity have been obtained over more traditional gas chromatographic–mass spectroscopic analytical techniques. All of the compounds tested were readily quantifiable at solution concentrations of 50 ppb, with linear correlations (r²>0.995) obtained over the range 50–300 ppb for the alkyltrimethylammonium bromides, and 50–200 ppb for neostigmine bromide. It is envisaged that, using this method, adsorption isotherms for these compounds on highly adsorbing activated carbons should be readily acquired.     

Thin-film microextraction coupled to LC-ESI-MS/MS for determination of quaternary ammonium compounds in water samples

The dual nature of the quaternary ammonium compounds, having permanently charged hydrophilic quaternary ammonium heads and long-chain hydrophobic tails, makes the sample preparation step and analysis of these compounds challenging. A high-throughput method based on thin-film solid-phase microextraction (SPME) and liquid chromatography mass spectrometry was developed for simultaneous quantitative analysis of nine benzylic and aliphatic quaternary ammonium compounds. Chromatographic separation and detection of analytes were obtained in reverse-phase mode in 8 min using a triple quadrupole mass spectrometer. Hydrophilic lipophilic balance particle-coated blades were found to be the most suitable among the different coatings tested in terms of recoveries and carryover on the blades. For desorption solvents, 70/30, v/v (A/B) with 0.1 % formic acid (where A is 10 mM ammonium acetate in acetonitrile/water (95/5?, v/v) and B is 0.1 %? (v/v) formic acid in isopropyl alcohol) was shown to be the most efficient solvent for the desorption of the analytes from the SPME sorbent. The SPME method was optimised in terms of extraction, pH, and preconditioning, as well as extraction and desorption times. Optimum conditions were 45 min of extraction time and 15 min of desorption time, all with agitation. The extraction was found to be optimum in a range of pH 6.0 to 8.0, which is consistent with the natural pH of water samples. Wide linear dynamic ranges with the developed method were obtained for each compound, enabling the application of the method for a wide range of concentrations. The developed method was validated according to the Food and Drug Administration criteria. The proposed method is the first SPME-based approach describing the applicability of the high-throughput thin-film SPME in a 96-well system for analysis of such challenging compounds.     

Separation and determination of quaternary ammonium compounds by high-performance liquid chromatography with a hydrophilic polymer column and conductometric detection

An HPLC method has been developed for separation and determination of long alkyl chain quaternary ammonium compounds. A column packed with a hydrophilic polymer packing, Shodex Asahipak GF-310 HQ, and a water–acetonitrile mixture containing 4,4′-bipyridyl and hydrochloric acid were used to depress hydrophobic adsorption of the quaternary ammonium compounds and increase the sensitivity of the conductometric detection with a micromembrane suppressor. Dodecyltrimethylammonium, cetyltrimethylammonium, tetradecyldimethylbenzylammonium and stearyltrimethylammonium ions can be completely separated from one another and quantified at 0.1 nmol level.     

Determination of low-molecular-mass quaternary ammonium compounds by capillary electrophoresis and hyphenation with mass spectrometry

The determination of quaternary ammonium ions by capillary electrophoresis (CE) is reviewed. The analytes include tetraalkylammonium and alkylbenzyldimethylammonium compounds frequently used as antiseptic and antibacterial agents as well as in various household products, several plant growth regulators and herbicides, by-products in bile acid sequestrants, and a range of anticholinergic drugs. Besides direct and indirect UV detection, hyphenation with electrospray mass spectrometry is particularly suited for quaternary ammonium ions and may lower the detection limits by two orders of magnitude. In comparison with established liquid chromatographic techniques, CE may exhibits superior separation efficiency. Applications in routine analysis have demonstrated that CE is reliable and robust enough to represent a real alternative to chromatography.     

Separation of alkylbenzyl quaternary ammonium compounds by capillary zone electrophoresis with sample stacking injection

Summary A systematic investigation of operational buffer systems, sample preparation and instrument parameters for achieving the best possible performance for determinating an homologous series of N-benzyl-N-alkyl-N,N-dimethylammonium chloride compounds by capillary zone electrophoresis with direct UV detection. The most effective separation was achieved within 3.5 min with the addition of acetonitrile (40%) in a phosphate buffer (20 mM pH 5.2) using a 40 cm fused-silica capillary operating at 25 KV and 20°C. Degassing of all electrolyte solutions and samples was very important. The linearity and repeatability for each compounds were satisfactory. To improve detection limits, on-column sample preconcentration, sample stacking, was investigated achieving a tenfold enrichment factor and quantitation limits about 10⁻⁷M.     

Photometric microtitrations. II

Summary A photometric titration method of microgram concentrations of zinc with dithizone as metallochromic indicator is described. The shape of the titration curve is most favourable for linear end-point extrapolation, if zinc is determined in a 50% ethanolic solution buffered with hexamethylenetetramine to ph 4.8–5.0. The optimum wavelength for the titration is 590 nm. For the concentration range of 2–20g of Zn²⁺ the relative error is ±1–2%. Interfering metals such as cadmium and lead may be masked by hydroxyethyldithiocarbamate.

---

Zusammenfassung Eine photometrische Titrationsmethode zur Bestimmung von Mikrogrammengen Zink mit Dithizon als metallochromer Indikator wurde beschrieben. Der Knick der Titrationskurve ist für die lineare Extrapolation des Endpunktes sehr günstig, wenn das Zink in 50%iger äthanolischer Lösung bestimmt wird, deren ph mit Hexamethylentetramin auf 4,8 bis 5,0 gepuffert wird. Die beste Wellenlänge für die Titration ist 590 nm. Für den Konzentrationsbereich 2 bis 20g Zn beträgt der relative Fehler ±1 bis 2%. Störende Metalle wie Cadmium und Blei lassen sich mit Hydroxyäthyldithiocarbamat maskieren.

---

Résumé On décrit une méthode de titrage photométrique du zinc en concentration de l'ordre du microgramme, par la dithizone, avec un indicateur métallochromique. La forme de la courbe de titrage se montre très favorable pour l'obtention par extrapolation linéaire du point équivalent, si l'on dose le zinc en solution éthanolique à 50%, tamponnée par l'hexaméthylènetétramine à ph 4,8–5,0. La longueur d'onde optimale pour le dosage est 590 nm. Pour les concentrations de l'ordre de 2–20g de Zn²⁺, l'erreur relative est de ±1–2%. Les métaux qui interfèrent, comme le cadmium et le plomb, peuvent être masqués par l'hydroxyéthyldithiocarbamate.

---

---

Dedicated to Prof. DSc.M. Jureek on the occasion of his 60th birthday.