Selective continuous monitoring and analysis of mixtures of acesulfame-K, cyclamate, and saccharin in artificial sweetener tablets, diet soft drinks, yogurts, and wines using filter-supported bilayer lipid membranes.

This work describes a technique for the rapid and sensitive electrochemical flow injection monitoring and analysis of mixtures of the artificial sweeteners acesulfame-K, cyclamate, and saccharin using stabilized systems of filter-supported bilayer lipid membranes (BLMs). Injections of artificial sweeteners were made into flowing streams of a carrier electrolyte solution, and a transient current signal with duration of seconds reproducibly appeared in less than < 1 min after exposure of the lipid membranes to the artificial sweeteners. The magnitude of this signal was linearly related to the concentration of artificial sweeteners, which could be determined at micromolar levels. Repetitive cycles of injection of artificial sweeteners have shown no signal degradation during each cycle (30 sequential injections). The time of appearance of the transient response was different for each artificial sweetener and increased in the order of cyclamic acid, acesulfame-K, and saccharin. The difference in time of response has allowed selective detection and analysis of these artificial sweeteners in mixtures. The effect of potent interferences, including a wide range of compounds usually found in foods, proteins, and lipids was investigated. The results showed no interferences from these constituents of real food samples. The major interference from proteins (most common in lipid-film-based biosensors) can be eliminated by modulation of the carrier solution that does not allow adsorption of these compounds in BLMs. The technique was applied in real food samples, that is, in artificial sweetener tablets, diet soft drinks, wines, and yogurts that contain mixtures of these artificial sweeteners with aspartame and other compounds. A comparison of results using the present method and that of an Official Method of Analysis showed good agreement between the two methods.

A minisensor for the rapid screening of sucralose based on surface-stabilized bilayer lipid membranes.

This work describes an electrochemical technique that is suitable for the rapid and sensitive screening of the sweetener sucralose based on surface-stabilized bilayer lipid membranes (s-BLMs) composed of egg phosphatidylcholine. The interactions of sucralose with s-BLMs produced electrochemical ion current increases, which appeared reproducible within a few seconds after exposure of the membranes to the sweetener. The mechanism of signal generation was investigated by differential scanning calorimetric studies. The mechanism was found to be associated with alteration of the electrostatic fields of the lipid film. These studies revealed that an increase of the molecular area of the lipids at the membranes and a stabilization of a gel phase structure occurred due to adsorption of the sweetener. Water molecules are adsorbed at the polar headgroups of the lipids, which changes the electrostatic field at the surface of the membranes. The current signal increases were related to the concentration of sucralose in bulk solution in the micromolar range. The present lipid film based sensor provided a fast response (i.e. in the order of a few seconds) to alterations of sucralose concentration (5-50 microm) in electrolyte solution. The electrochemical transduction of the interactions of this artificial sweetener with s-BLMs was applied in the determination of this compound in granulated sugar substitute products using the present minisensor.