Osman Sagdic, in Saffron, 2021 3.3.3 Soxhlet extraction The technique has also been combined with microwave-assisted extraction and ultrasonic extraction in an attempt to improve extraction efficiencies.Įxamples of the use of Soxhlet for trace contaminant analysis include the determination of polycylic aromatic hydrocarbons (PAHs) 8 and polychlorinated biphenyls (PCBs). The traditional methods use a significant volume of organic solvent (50–200 ml for a 10-g sample), although automated systems enable smaller volumes of solvents to be used. Using the automated systems that are now available, several samples can be extracted simultaneously, reducing the time required for extraction (typically 1–6 h). The technique is not selective (apart from the choice of extraction solvent) and generally further cleanup and concentration are required. The extraction solvent is continuously cycled though the matrix, by boiling and condensation, with the sample being collected in the hot solvent. Soxhlet extraction is an exhaustive extraction technique widely applied to analytes that are sufficiently thermally stable. Lalljie, in Comprehensive Sampling and Sample Preparation, 2012 3.40.3.1 Soxhlet Extraction One report described extraction of chlorinated phenols from a textile sample using an organic solvent, followed by injection for CE without additional treatment and separation using a nonaqueous run buffer. Since the extract volume is much larger than a typical injection volume for CE, the solvent is reconstituted in a CE separation solution after evaporation and then injected into the capillary. However, it requires a long extraction time and the consumption of a large amount of solvent. Soxhlet extraction is a rugged, well-established technique and permits unattended extraction. By refluxing the solvent through the thimble using a condenser and a siphon side arm, the extraction cycle is typically repeated many times. A porous thimble loaded with a solid sample is placed inside the main chamber of the Soxhlet extractor. Soxhlet extraction has traditionally been used for a solid sample with limited solubility in a solvent in the presence of insoluble impurities. Chung, in Comprehensive Sampling and Sample Preparation, 2012 3.35.2.3.1 Soxhlet Extraction Additionally, automation of the Randall–Soxhlet method can be performed more easily, which led to incorporation of the automated SOX method by the US EPA. Closing a solvent return valve and careful evaporation enables integrated sample concentration. Following this extraction step, the thimble is raised above the boiling solvent until residual extract is removed. This enhances the extraction speed since analytes are more soluble in hot solvent. Here, the sample is immersed in the boiling solvent until the desired extraction takes place. The extraction time can be drastically reduced by modification of the Soxhlet procedure as proposed by Randall in the mid-1970s. 3) Continuous repetition of the extraction. Solutes are transferred from the extraction chamber into the reservoir. 2) Condensation and extraction with “fresh” solvent. 1) Solid matrix is placed in SOX thimble. Schematic illustration of the workflow of SOX. The underlying principles, instrumentation and operational procedures are described.įigure 5.15. The focus is on recent developed and commercially available modifications, which includes automated Soxhlet extraction, focused microwave-assisted Soxhlet extraction, ultrasound-assisted Soxhlet extraction, high-pressure Soxhlet extraction and fluidized bed extraction. This chapter covers Soxhlet-related techniques aimed at improvement of traditional Soxhlet performance by using auxiliary energies and automation. New approaches of this technique have been implemented to reduce extraction times and extractant volumes. Over the years, an intensive research on different modifications has been carried out in order to overcome the main disadvantages of conventional Soxhlet technique. Up to this day, Soxhlet extraction technique remains a standard technique to which the performance of modern extraction techniques is compared. Since its discovery in 1879, the standard Soxhlet technique has been routinely applied in almost every analytical laboratory. Soxhlet extraction is one of the most popular techniques for extraction of analytes from solid materials. Namieśnik, in Comprehensive Sampling and Sample Preparation, 2012 Abstract
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