Simultaneous Distillation−Extraction: Theoretical Model and Development of a Preparative Unit

Simultaneous distillation−extraction (SDE) is routinely used by analysts for sample preparation prior to gas chromatography. As the GC profile of the isolated volatiles must be representative of the original sample, the limits of SDE applicability should be known. In this paper, an equation which agrees very well with the experimental rate of pyridine recovery is proposed. Consequently, the influence of various operating parameters can be simulated. In addition, the recovery of a given molecule can be deduced from its relative volatility and water/solvent partition coefficient. A new preparative device was developed on the basis of these observations. It allows the isolation of volatiles from a matrix at atmospheric pressure, or under vacuum, at room temperature. Therefore, the formation of thermal artifacts is reduced. A distillation column was added in the solvent side to limit possible redistillation. Extraction and separation steps were separated, and the extraction efficiency was improved to increase recovery rates.