Modification of the properties of NaDS micellar solutions by adding electrolytes and non-electrolytes: investigations with decyl eosin as a pKa-probe

Loginova, Lidia P.; Samokhina, Larisa V.; Mchedlov‐Petrossyan, Nikolay O.; Alekseeva, V. I.; Savvina, L. P.

doi:10.1016/s0927-7757(01)00741-5

Cited by 26 publications

(15 citation statements)

References 40 publications

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“…The l max = 500 nm value of n-decylfluorescein anion, R -, coincides with that in SDS micelles, while in the case of n-decyleosin the band position (542 nm) is closer to those in nonionic and cationic micelles (540-544 nm), than in anionic ones (535 nm). 29 The pK a app value of n-decyleosin, determined within the pH 0.5-3.0 (Table 3), is with 1.73 lower than the value 2.61 in micellar solutions of nonionic Tween-80, and even more so than pK a app = 4.53 in SDS micellar media at an ionic strength of 0.05 mol L -1 (NaCl). 29 In fact, the behavior of the lipophilic dyes in gelatin solutions is in agreement with the re-charging of the gelatin macromolecule on going from pH < 5 to pH > 5 in the aquatic medium.…”

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confidence: 89%

“…29 The pK a app value of n-decyleosin, determined within the pH 0.5-3.0 (Table 3), is with 1.73 lower than the value 2.61 in micellar solutions of nonionic Tween-80, and even more so than pK a app = 4.53 in SDS micellar media at an ionic strength of 0.05 mol L -1 (NaCl). 29 In fact, the behavior of the lipophilic dyes in gelatin solutions is in agreement with the re-charging of the gelatin macromolecule on going from pH < 5 to pH > 5 in the aquatic medium.We also determined the pK a app values of bromocresol green and neutral red in gelatin solution (Table 4). Contrary to the lipophilic xanthenes, the binding of the dyes species seems to be not complete, judging from the positions of their absorption maxima, and hence the discussion of the pK a app values is not appropriate here.…”

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confidence: 89%

“…10,[28][29][30][31][32][33] The dyes of such type are also utilized in sensor devices 31,34,35 and for holographic record. 32 We studied visible-spectroscopically the protolytic properties of four xanthene dyes: eosin, ethyl eosin, n-decyleosin, and n-decylfluorescein, two sulfonephthaleins: bromophenol blue and bromocresol green, a triphenylmethane dye malachite green, and an azine dye neutral red in the films, by measuring their transmittance after immersing them into aqueous buffer solutions of different pH.…”

Section: Introductionmentioning

confidence: 99%

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Protolytic properties of dyes embedded in gelatin films

Никитина¹,

Reshetnyak²,

Svetlova³

et al. 2011

J. Braz. Chem. Soc.

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O filme de gelatina endurecida fixo em uma base transparente de triacetilcelulose pode ser utilizado como um suporte conveniente para indicadores ácido-base. Azul de bromofenol, verde de bromocresol, eosina, etil-eosina, n-decil-eosina, n-decil-fluoresceína, vermelho neutro e verde de malaquita foram incorporados nos filmes de gelatina por extração em meio aquoso sob condições apropriadas. A absorção de luz dos filmes dopados com corante exibe uma resposta ao pH de soluções tampão aquosas nas quais foram imersos. Valores reprodutíveis das constantes aparentes de dissociação dos indicadores, pK a app , foram calculados pelo tratamento convencional dos valores de pH do tampão aquoso e também para a água absorvida nos filmes de gelatina. Os experimentos com pH abaixo e acima do ponto isoelétrico da gelatina (em torno de pH 5) resultaram em valores de pK a app semelhantes àqueles em meios micelares de tensoativos catiônicos e aniônicos, respectivamente. Os filmes de gelatina modificados por corantes podem ser recomendados para uso em sensores óticos e dispositivos similares.The hardened gelatin film fixed on the transparent triacetylcellulose support can be utilized as a convenient carrier for acid-base indicator dyes. Bromophenol blue, bromocresol green, eosin, ethyleosin, n-decyleosin, n-decylfluorescein, neutral red, and malachite green were embedded into the gelatin films by extracting from aqueous media under appropriate conditions. The light absorption of dye-doped films exhibits a response to the pH values of aqueous buffer solutions, where they were soaked in. The well-reproducible indices of the apparent ionization constants, pK a app , of the indicators were calculated by conventional equating the pH values of the bulk aqueous buffer and those of the 'internal' water into the gelatin films. The experiments with pH below and above the isoelectric point of gelatin (around pH 5) result in pK a app values, which resemble those in micellar media of cationic and anionic surfactants, respectively. The dye-modified gelatin films can be recommended for use in optical sensors and related devices. Keywords: dye-modified gelatin film, indicators, apparent ionization constants, medium effects IntroductionThis paper is devoted to the influence of hardened gelatin media on the spectral and acid-base properties of immobilized xanthene, sulfonephthalein, and some other dyes.The immobilization of reagents in solid matrix (cellulose, ion-exchangers, polymers, silica, xerogels, etc.) 1-7 or using organized solutions, e.g., surfactant-based ones, [8][9][10][11][12] modifies the properties of guest molecules owing to the change of the microenvironment.Such modifications, or medium effects, are most studied and well documented for acid-base indicators. 8,9 In this case, the influence of the microenvironment results in the shift of the indicator equilibrium as compared to that in aqueous media. The main reasons are the local polarity and the local electrical charge. The latter often (but not always) manifests itself in the decre...

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confidence: 89%

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confidence: 89%

Section: Introductionmentioning

confidence: 99%

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Protolytic properties of dyes embedded in gelatin films

Никитина¹,

Reshetnyak²,

Svetlova³

et al. 2011

J. Braz. Chem. Soc.

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“…Note that, in the nonionic and cationic microemulsions, as well as in 98.7% 1-butanol, l max and dissociation constants of these compounds are much closer (Tables 134). Therefore, such an unusual behavior of compound III in the systems with anionic surfactants can be attributed to a particularly strong hydration of the surface of microemulsion droplets (high hydrophilicity of the surface of SDS micelles is well known [7,9,19]). The inner surface of the microdroplets is hydrophobic, and the polarity drop in this case is more pronounced than in the other microemulsions.…”

Section: Microemulsions Based On Anionic Surfactantmentioning

confidence: 99%

“…Since changing fraction of the surfactant on the surface of SDS micelles, i.e., [dilution] of charged groups with the alcohol, decreases |Y| and pK a ac [19], we have no choice but to suggest that this ratio only slightly changes on the microdroplet surface, and the excess of 1-pentanol is dissolved in the inner, [hydrocarbon] range of the pseudophase.…”

Section: Microemulsions Based On Anionic Surfactantmentioning

confidence: 99%

Reichardt betaines as combined solvatochromic and acid-base indicators in microemulsions

2004

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Protolytic equilibria and absorption spectra of four solvatochromic Reichardt betaines different in their hydrophobicity are studied in direct microemulsions hydrocarbon3alcohol3surfactant3water (three different hydrocarbons, three alcohols, and seven surfactants including nonionic, cationic, and anionic ones were tested). Localization of even the most lipophilic betaines corresponds to the polarity index E N T of no less than 0.4, so that the occurrence of a purely hydrocarbon core in the microdroplets is unlikely probable. The apparent dissociation constants of the indicators are determined, and their dependence on the composition and concentration of the microemulsions is discussed.

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Fluorescent Sensors for Hg²⁺ in Micelles: A New Approach that Transforms an ON–OFF into an OFF–ON Response as a Function of the Lipophilicity of the Receptor

Pallavicini

Fernandez

Foti

et al. 2006

Chemistry A European J

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A new approach to the use of micelles in the fluorescent sensing of metal cations is proposed and applied to the case of Hg2+. We demonstrate how it is possible to transform a system from an ON–OFF to an OFF–ON sensor by changing the length of the chain used to lipophilise a ligand that resides inside TritonX‐100 micelles together with pyrene as the fluorophore. Three tetrathia‐monoaza macrocyclic ligands have been synthesised with the same ring but functionalised on the nitrogen atom with a methyl (C1‐NS4), an n‐butyl (C4‐NS4) or an n‐dodecyl (C12‐NS4) chain. The three ligands have been fully characterised in water containing TritonX‐100 micelles by means of potentiometric titrations and their apparent protonation and complexation constants with Hg2+ were determined. On the basis of the distribution diagrams obtained, the more lipophilic C12‐NS4 has been developed as an ON–OFF fluorescent sensor for mercury: working at pH<4, in the absence of Hg2+ the ligand is inside the micelles, protonated and non‐quenching, while on addition of mercury the [C12‐NS4Hg]2+ complex forms which remains inside the micelles and is quenching. On the other hand, the ligand of intermediate chain length, C4‐NS4, can be used to obtain an OFF–ON sensor at 7.07.0 the ligand is unprotonated, it stays inside the micelles and is quenching, while addition of Hg2+ in the 7.0–9.5 pH range results in the formation of [C4‐NS4Hg]2+, which is hydrophilic enough to leave the micelles and to be released into the bulk solution where it is no longer capable of quenching pyrene fluorescence. Additional studies on C1‐NS4, C3‐NS4 and C8‐NS4 indicate that the optimal chain length to observe this OFF–ON behaviour is C3–C4.

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Modification of the properties of NaDS micellar solutions by adding electrolytes and non-electrolytes: investigations with decyl eosin as a pKa-probe

Cited by 26 publications

References 40 publications

Protolytic properties of dyes embedded in gelatin films

Protolytic properties of dyes embedded in gelatin films

Reichardt betaines as combined solvatochromic and acid-base indicators in microemulsions

Fluorescent Sensors for Hg²⁺ in Micelles: A New Approach that Transforms an ON–OFF into an OFF–ON Response as a Function of the Lipophilicity of the Receptor

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Modification of the properties of NaDS micellar solutions by adding electrolytes and non-electrolytes: investigations with decyl eosin as a pKa-probe

Cited by 26 publications

References 40 publications

Protolytic properties of dyes embedded in gelatin films

Protolytic properties of dyes embedded in gelatin films

Reichardt betaines as combined solvatochromic and acid-base indicators in microemulsions

Fluorescent Sensors for Hg2+ in Micelles: A New Approach that Transforms an ON–OFF into an OFF–ON Response as a Function of the Lipophilicity of the Receptor

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Fluorescent Sensors for Hg²⁺ in Micelles: A New Approach that Transforms an ON–OFF into an OFF–ON Response as a Function of the Lipophilicity of the Receptor