Automatic ionic liquid-enhanced membrane microextraction for the determination of melamine in food samples

- Innovative miniaturized automatic methodology for melamine determinations.
- Integration of an in-line microextraction and quantification processes in the same system.
- Assembly of an extraction unit with a hydrophilic microporous membrane in the system.
- Ionic liquid used as extractant, instead of an organic hazardous solvent.
- Melamine potentiates the peroxidase catalyzed oxidation of sesamol by hydrogen peroxide.

An innovative miniaturized automatic methodology for the separation of melamine by a hydrophilic microporous membrane and its quantification is proposed. For that an extraction unit containing a hydrophilic microporous membrane was assembled to the system. In the acceptor solution it was used a 10% ionic liquid aqueous solution, instead of an organic hazardous extractant, with an added advantage of the separation process allows the quantification of melamine in liquid samples without any previous treatment. The melamine potentiated the peroxidase catalyzed oxidation of sesamol by hydrogen peroxide with the formation of a fluorescent compound. The effect of physical and chemical parameters in the extraction process and also in the enzymatic reaction used for the quantification of melamine was evaluated. The developed methodology showed detection and quantification limits of 0.07 and 0.22 mg L−1, respectively, and linear range up to 3.00 mg L−1, allowing accurate quantifications of melamine in the concentrations range imposed by food agencies, in a total analysis time of around 5 min (including the extraction process). The novel methodology was applied to milk, powder milk, soy milk and yogurt samples in a precise and accurate fashion. With the sequential injection analysis tool a simple, versatile, rapid, and robust automatic system was implemented avoiding in batch sample pretreatment. Furthermore, the reduction of chemicals consumption and waste generation fulfilled the current recommendations and trends of Green Chemistry.