Automated Soxhlet

Soxtherm can be used for a variety of substrates, such as plasticisers, and additives in plastics and rubber, fibre and textile coatings, colorants on textiles, fat in food, oils and lubricants, fertiliser coatings, etc. Specific reports are scarce. EPA method 3541 has adopted automated Soxhlet extraction [151]. 

U.S. Environmental Protection Agency (EPA), Method 3541, Automated Soxhlet Extraction (September 1994). 

Polycyclic aromatic hydrocarbons Automated Soxhlet extraction with ethyl acetate [85]... 

U.S. EPA. 1994. Method 3541 Automated Soxhlet Extraction 1.0. Scope and application. 

This chapter covers techniques for the extraction of semivolatile organics from solid matrices. The focus is on commonly used and commercially available techniques, which include Soxhlet extraction, automated Soxhlet extraction, ultrasonic extraction, supercritical fluid extraction (SFE), accelerated solvent extraction (ASE), and microwave-assisted extraction (MAE). The underlying principles, instrumentation, operational procedures, and selected applications of these techniques are described. In a given application, probably all the methods mentioned above will work, so it often boils down to identifying the most suitable one. Consequently, an effort is made to compare these methodologies. 

The U.S. Environmental Protection Agency (EPA) has approved several methods for the extraction of pollutants from environmental samples. These standard methods are listed under EPA publication SW-846, Test Methods for Evaluating Solid Waste Physical/Chemical Methods [1], Many of them were approved only in the last decade. Automated Soxhlet was promulgated in 1994, SFE and ASE in 1996, and MAE in 2000. The Association of Official Analytical Chemists (AOAC) has published its own standard extraction methods for the food, animal feed, drug, and cosmetics industries [2], Some extraction methods have also been approved by the American Society for Testing and Materials (ASTM) [3], Table 3.1 summarizes the standard methods from various sources. 

Soxhlet extraction and automated Soxhlet extraction are described in this section. Soxhlet extraction was named after Baron Yon Soxhlet, who introduced this method in the mid-nineteenth century. It had been the most widely used method until modern extraction techniques were developed in the 1980s. Today, Soxhlet is still a benchmark method for the extraction of semivolatile organics from solid samples. Automated Soxhlet extraction (Soxtec being its commercial name) offers a faster alternative to Soxhlet, with comparable extraction efficiency and lower solvent consumption. 

Distillation Soxhlet extraction and automated Soxhlet extraction... 

A fuUy automated Soxhlet extraction has been patented as Soxtec by Foss Tecator (Sweden) based on a four-step solvent extraction technique. The sample is rapidly dissolved during the first step in boiling solvent. The remaining soluble matter is efficiently removed at the second step, whUe distilled solvent is collected at the third step. In the fourth step, the sample cup lifts off the hot plate, utilizmg residual heat to predry while eliminating boil-dry risk. 

Automated Soxhlet extraction Polychlorinated biphenyls, organochlorine pesticides and semi-volatiles from soils, relatively dry sludges and solid wastes Allows equivalent extraction efficiency to Soxhlet extraction in 2 h... 

The improvements in Soxhlet extractions are high-pressure Soxhlet extraction (HPS), automated Soxhlet extraction (Soxhlet HT and Buchi B811) and focused microwave-assisted Soxhlet extraction (Soxwave and FMASE) as shown by Luque de Castro MD and Garcia-Ayuso in 1998. The solvents used for extraction are polar species (dimethyl formamide,... 

Szolar, O. H., Rost, H., Braun, R., and Loibner, A. P., Analysis of polycyclic aromatic hydrocarbons in soil minimizing sample pretreatment using automated Soxhlet with ethyl acetate as extraction solvent. Anal. Chem., lA, 2379-2385, 2002. 

U.S. Environmental Protection Agency (EPA), Method 3541 Automated Soxhlet Extraction, Revision 0, In Online Test Methods for Evaluating Solid Waste Physical/Chemical Methods (SVP-846), Office of Sohd Waste, 1994, http //www.epa.gov/epaoswer/hazwaste/test/pdfs/3541. 

Two validation studies conducted in 1994 compared ASE with S-LSE, automated Soxhlet, and wrist-shake or manual LLE for the determination of target analytes from solid wastes of interest to TEQA. These results are summarized in Table 3.3. ASE proved equivalent to the conventional procedures. The data generated in these two studies resulted in the generation of EPA Method 3545 that received final promulgation in June 1997 as part of SW-846 Method Update III (25). 

For many years, the traditional sample preparation methods, such as the Soxhlet extraction, were applied. Most of these methods have been used for more than 100 years, and they mostly require large amounts of organic solvents. These methods were tested during those times, and the analysts were familiar with the processes and protocols required. However, the trends in recent years are automation, short extraction times, and reduced organic solvent consumption. Modern approaches in solid sample preparation include microwave-assisted solvent extraction (MASE), pressurized liquid extraction, accelerated solvent extraction (ASE), matrix solid-phase dispersion (MSPD), automated Soxhlet extraction, supercritical fluid extraction (SEE), gas-phase extraction, etc. 

Sherma, J. Modem sample preparation technology, n. Automated SPME, ASE, SEE, MAE, automated Soxhlet extraction. Inside Lab. Manag. 2001, 5 (6), 33-38. 

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