Use of the three-phase model and headspace analysis for the facile determination of all partition/association constants for highly volatile solute–cyclodextrin–water systems

Abstract

A versatile method for measuring the partition coefficients of volatile analytes with an aqueous pseudophase using headspace gas chromatography is reported. A "three-phase" model accounts for all equilibria present in the system, including the partitioning of the analyte in the gas and aqueous phases to the pseudophase. This method is applicable to a wide variety of volatile analytes and aqueous pseudophases, providing that sufficient pseudophase may be used to reduce the analyte partial pressure. Generally, the method offers good reproducibility and high sensitivity. The associations of five volatile analytes (hydrogen sulfide, methanethiol, dimethyl sulfide, dichloromethane, and ethyl ether) with various cyclodextrins were examined. All analytes were found to partition preferentially to the cyclodextrin pseudophase compared to the aqueous phase. In addition, several analyte-cyclodextrin combinations formed insoluble complexes in solution that enhanced the extraction of the analyte from the gas and aqueous phases. Derivatization of the cyclodextrins generally decreased the extent of analyte-cyclodextrin interaction.

A review on cyclodextrin encapsulation of essential oils and volatiles

“…[146][147][148][149] In the thermo-analytical system (TAS) the sample is heated in a sealed glass tube equipped with a capillary outlet. The products in the vapour or gaseous state, leave through the capillary tube then condense directly onto a thin-layer chromatographic plate.…”

Gas–liquid partitioning of halogenated volatile organic compounds in aqueous cyclodextrin solutions

“…Although to a lesser extent, the fluorination of the methyl group of toluene also increases the stability of its complex with b-CD. Also, 1-chlorobutane and methoxyflurane showing much higher complex stabilities with both a-CD and b-CD than their halogen-free straight alkyl chain analogs, n-pentane [37] and diethyl ether [10], respectively, support the positive effect of guest halogenation on the binding affinity.…”

“…These studies further differ in the strategy through which the extent of binding as a function of the reactants' concentrations is examined as well as in the fact whether the explicit calibration of gas chromatographic response is needed. The studies have dealt with a number of VOCs, involving alkan-1-ols [4,5], alkanes [6], cycloalkanes [6], alkylbenzenes [3,6,9], and some sulfur or chlorine derivatives [8,10].…”

Solubilisation of chlorinated solvents by cyclodextrin derivativesA study by static headspace gas chromatography and molecular modelling

“…As a consequence, they can play a major role in environmental science in terms of solubilisation of organic contaminants, enrichment and removal of organic pollutants and heavy metals from soil, water and atmosphere [10][11][12][13][14]. CDs can immobilize VOCs into the cavity in the aqueous phase [15][16][17]. In this way, they are expected to improve the transfer between gaseous and aqueous phase during the absorption process.…”