Two-phase photometric ion-pair titrations of drugs and surfactants

Mohammed, Hussain Y.; Cantwell, Frederick F.

doi:10.1021/ac50053a040

Cited by 29 publications

(28 citation statements)

References 4 publications

(7 reference statements)

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“…[11][12][13][14][15]18 All these reports indicate that, in solution, an ion-pair can be formed between a sulphonate anionic site and a quaternary ammonium compound. None of the papers reported on the possible ion-pairing between a protonated alkylamine, such as diethylammonium or triethylammonium cations, and a sulphonate group.…”

Section: Alkali Cation Displacement Mechanismmentioning

confidence: 99%

The Use of Diethylamine to Determine the Number of Sulphonate Groups Present Within Polysulphonated Alkali Metal Salts by Electrospray Mass Spectrometry

Ballantine

Games

Slater

1997

Rapid Commun. Mass Spectrom.

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By using negative-ion diethylamine (DEA)-enhanced electrospray mass spectrometry under mild dissociative conditions, (a low voltage applied across the sampling cone aperture) a number of DEA molecules were observed to associate with the doubly charged acid ion of polysulphonated salts to form a series of higher-mass peaks. As the cone voltage was increased, these peaks degenerated into a series of lower-mass peaks. Each of the peaks contained within these series was separated by the mass of one DEA molecule. By further increasing the cone voltage, it was possible to dissociate all the DEA adducts from the acid ion.The maximum number of DEA molecules associated with the doubly charged acid ion could be correlated with the number of sulphonate sites present. This technique correctly identified the number of sulphonate groups contained within the series of compounds tested. A mechanism for these processes, based on the ability of protonated DEA to form ion pairs with sulphonate sites, is advanced. © 1997 by John Wiley & Sons, Ltd. Received 11 September 1996; Revised 17 February 1997; Accepted 17 February 1997 Rapid. Commun. Mass Spectrom. 11, 630-637 (1997 Polysulphonated salts are notorious for producing mass spectrometry signals of low intensity. 1 We have already shown that the addition of a basic amine to a polysulphonate in solution will dramatically enhance the signal intensity of the acid ions and just those fragment ions which had retained the capability to associate with alkali metal ions prior to diethylamine (DEA) intervention. All the signals which were due to alkali-metal association were greatly reduced or eliminated by the addition of DEA. 2,3 This unusual behaviour was further investigated and it was discovered that, under very mild ionization conditions, a number of DEA molecules could be seen attached to the acid ions. The maximum number of attached DEA molecules observed in any particular charge state was directly related to the number of sulphonate sites present on the compound tested.This paper discusses the relationship between the maximum number of adducted DEA molecules and the number of sulphonate sites, and how this relationship can be applied to determine the number of sulphonate sites in a series of polysulphonated salts. We also propose a possible mechanism for this process together with some experimental data to support our assumptions. EXPERIMENTAL Materials and methodsChemicals. All alkylamines and potassium indigo tetrasulphonate were purchased from Aldrich Chemical Co.Ltd. (Gillingham, Dorset, UK) and were used without further purification. Samples of Direct Blue 98, Direct Red 80, Direct Red 81, Direct Green 26, Acid Yellow 23, and Acid Orange 52 were all kindly donated by Dr. Peter Douglas and Richard Philips, Department of Chemistry, University of Wales, Swansea. Zeneca Colours S69177, S54412, and S69417 were all donated by Zeneca Ltd and used without further purification. Figure 1 shows the structures of the polysulphonates used in this investigation.Sample preparation. All an...

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Section: Alkali Cation Displacement Mechanismmentioning

confidence: 99%

The Use of Diethylamine to Determine the Number of Sulphonate Groups Present Within Polysulphonated Alkali Metal Salts by Electrospray Mass Spectrometry

Ballantine

Games

Slater

1997

Rapid Commun. Mass Spectrom.

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“…[7], [13], and [18]. Therefore, it is important to demonstrate that interfacial adsorption of the sample is negligible, as previously described (14,16). With especially large or surface-active organic ions adsorption may present a problem.…”

Section: Resultsmentioning

confidence: 97%

“…Dissociation of ion-pairs in the organic phase is often negligible (1,(12)(13)(14)(15). However, the tendency toward dissociation is greater when the ions involved are less hydrophobic and when the solvent is more polar (1,2).…”

Section: Ion-pair Clissociarionmentioning

confidence: 99%

“…incrementally alter the composition of the system, such as in two-phase titrations and distribution isotherm measurements (12)(13)(14)(15)(16)(17). This characteristic makes the "filter-probe" an obvious device to use in solvent extraction studies designed to evaluate associationldissociation equilibria, because such studies are necessarily done as a function of changing sample concentration.…”

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confidence: 99%

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Measurement of self-association and ion-pair dissociation constants by solvent extraction using a membrane phase separator

Carmichael¹,

Cantwell²

1982

Can. J. Chem.

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The "filter-probe" membrane phase separator is used with a gravimetric buret to obtain the following constants at 25 °C by measuring solvent-extraction isotherms: dimerization constant of benzoic acid in chloroform (log K2,HBz = 2.12 ± 0.01); "self-ion-pair extraction" constant of Naloxone into chloroform [Formula: see text]; and ion-pair dissociation constant of tetraethylammonium picrate in methylene chloride (log Kdiss = −4.52 ± 0.09).

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“…[2] The ability of quaternary ammonium compounds to form an extractable ion-pair with an anionic dye has been described. [3,4] The ion-pair technique has proved of value for the assay of amines. It is based on the property of these compounds to form ion pairs with ions of opposite charges.…”

Section: Introductionmentioning

confidence: 99%

Spectrofluorometric Determination of Tiotropium Bromide by Ion Pair Extraction Using 9, 10 Dimethoxyanthracene-2-sulphonate Sodium

Ahmed

Clark

2007

Journal of Ion Exchange

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A rapid, simple and specific fluorometric procedure is described for the analysis of the anticholinergic drug, tiotropium bromide (TIO) in bulk and in capsule formulation. The method is sensitive and is based on the reaction of this drug as a quaternary ammonium compound with the fluorogenic reagent 9, 10-dimethoxyanthracene-2-sulphonate (DMOAS) as counter ion in acidic medium and the proposal of the reaction pathway was postulated. The hydrophobic ion-pair formed was extracted in dichloroethane and measured spectrofluorometrically at 450 nm after excitation at 385 nm. The fluorescence intensity-concentration plot was rectilinear over the ranges of 7-30 ng m1-1 y=mx+b, r2=0, 9991 (m =12.054; b =156.27).The detection limit was 0.0326 ng ml-1 based upon United States Pharmacopeia (USP 2002). The different parameters affecting the reaction pathway were studied and optimized. The proposed method was successfully applied to the analysis of tiotropium capsules. No interference was observed from pharmaceutical excepients such as lactose.

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Two-phase photometric ion-pair titrations of drugs and surfactants

Cited by 29 publications

References 4 publications

The Use of Diethylamine to Determine the Number of Sulphonate Groups Present Within Polysulphonated Alkali Metal Salts by Electrospray Mass Spectrometry

The Use of Diethylamine to Determine the Number of Sulphonate Groups Present Within Polysulphonated Alkali Metal Salts by Electrospray Mass Spectrometry

Measurement of self-association and ion-pair dissociation constants by solvent extraction using a membrane phase separator

Spectrofluorometric Determination of Tiotropium Bromide by Ion Pair Extraction Using 9, 10 Dimethoxyanthracene-2-sulphonate Sodium

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