Acid-base properties and solubility of pindolol, diazepam and chlordiazepoxide in SDS micelles.
ABSTRACT The effect of sodium dodecyl sulphate (SDS) on the acid-base properties and on the solubility of a beta-blocker (pindolol) and of two benzodiazepines (diazepam and chlordiazepoxide) has been assessed. The study was performed by potentiometric and spectrophotometric determinations of the acidity constants and by spectrophotometric evaluation of the solubilities of the pharmaceutical drugs in aqueous solution and in solutions to which was added SDS with concentrations below and above the critical micelle concentration (cmc), at 25 degrees C and at an ionic strength 0.1 M (NaCl). The effect of the organized assemblies on the pKa values was quantified by the application of two theoretical models that differ in the inclusion of ionic exchange between positively charged species in solution. These models have allowed the determination of the binding constants for drug/micelle and yielded values in good agreement with those obtained by the solubility method, and in addition provide a more detailed picture of the effect of drug charge on its partition. The results can be taken to evidence different interaction modes of the drugs with the SDS micelles.
- SourceAvailable from: Alexander Boichenko[show abstract] [hide abstract]
ABSTRACT: The apparent dissociation constants of 1-propanoic, 1-butanoic, 1-pentanoic and 1-hexanoic acids were obtained for the first time in Brij 35 micellar solutions with concentration from 0.03 to 0.20mol⋅L−1 and sodium dodecyl sulfate (SDS) micellar solutions with concentrations from 0.01 to 0.30mol⋅L−1. A pronounced effect of Brij 35 micelles on the acid-base properties of aliphatic acids was observed. The binding constants, K b, of carboxylic acids to micellar pseudophases of SDS and Brij 35 were estimated within the framework of the pseudophase model. The dependences of Gibbs energies of transfer from water to the micellar pseudophases were constructed, and Gibbs energies were evaluated for methylene and carboxylic group transfers into Brij 35 and SDS micelles. Comparison of the Gibbs energies of methylene group transfer from water to Brij 35 and SDS suggests that the mechanisms of hydrocarbon group transfer into the core of nonionic and anionic micelles involving the same monomer hydrophobic tail length are similar. KeywordsMicellar media effect–Solubilization–Carboxylic acids–Apparent dissociation constant–Sodium dodecyl sulfate–Brij 35Journal of Solution Chemistry 04/2012; 40(6):968-979. · 1.13 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: The potential effects of adjuvants, including surfactants used in pesticide formulation, have been extensively studied for many small organic chemicals, but similar investigation on pesticides is limited in most cases. Solubilizing effects leading to the apparently increased water solubility of a pesticide are commonly known through the preparation of formulations, but fundamental profiles, especially for a specific monodisperse surfactant, are not fully studied. Reduced volatilization of a pesticide from the formulation can be explained by analogy of a very simple organic chemical, but the actual mechanism for the pesticide is still obscure. In contrast, from the point of view of avoiding groundwater contamination with a pesticide, adsorption/desorption profiles in the presence of surfactants and adjuvants have been examined extensively as well as pesticide mobility in the soil column. The basic mechanism in micelle-catalyzed hydrolysis is well known, and theoretical approaches including the PPIE model have succeeded in explaining the observed effects of surfactants, but its application to pesticides is also limited. Photolysis, especially in an aqueous phase, is in the same situation. The dilution effect in the real environment would show these effects on hydrolysis and photolysis to be much less than expected from the laboratory basic studies, but more information is necessary to examine the practical extent of the effects in an early stage of applying a pesticide formulation to crops and soil. Many adjuvants, including surfactants, are biodegradable in the soil environment, and thus their effects on the biodegradation of a pesticide in soil and sediment may be limited, as demonstrated by field trials. Not only from the theoretical but also the practical aspect, the foliar uptake of pesticide in the presence of adjuvants has been investigated extensively and some prediction on the ease of foliar uptake can be realized in relation to the formulation technology. However, effect on root uptake of pesticides is to be further investigated. In an aqueous environment more or less contaminated by various chemicals such as detergents and their degradates, it is necessary to investigate the effect of adjuvants on uptake, bioconcentration, and trophic transfer of pesticides for better understanding of pesticide contamination of aquatic species in the aquatic environment.Reviews of environmental contamination and toxicology 02/2008; 194:71-177. · 4.13 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: It is already recognised that heavy-atom-induced, room-temperature phosphorescence can be used to determine pindolol in pharmaceutical samples and biological fluids. We describe here a new, simple, rapid and selective development of this technique. The phosphorescence signals derive from the interaction of pindolol with a relatively high concentration of heavy-atom salts in the presence of sodium sulphite as oxygen scavenger. Phosphorescence was registered in the presence of 1.2 M potassium iodide, 15 mM sodium sulphite and 30% v/v methanol at 450 nm, exciting at 285 nm. The detection limit was 21.1 ng mL(-1). The method has been successfully applied to the determination of pindolol in commercial pharmaceutical tablets, urine and blood serum.Analytical and Bioanalytical Chemistry 04/2007; 387(5):1945-8. · 3.66 Impact Factor