Soxhlet extraction: Past and present panacea

An overview of Soxhlet extraction, the advantages and shortcomings of this centenary technique as well as the attempts to improve its performance and achievements reached is here presented. Assistance of high pressure, ultrasound or microwaves has decreased or minimized the negative characteristics of the conventional extractor. Automation of Soxhlet performance opened the door to commercialization of a number of different approaches. The evolution of Soxhlet extractor is here critically discussed, and the conclusion from this overview is that the adoption of new technologies to improve its performance converts Soxhlet extraction in almost a "panacea" in this field.

Pressurised liquid extraction–comprehensive two-dimensional gas chromatography for fast-screening of polycyclic aromatic hydrocarbons in soil

Pressurised liquid extraction (PLE) was applied to the extraction of polycyclic aromatic hydrocarbons (PAHs) from contaminated soils from Husarviken in Stockholm, Sweden. The extraction step was followed by conventional gas chromatography (GC), comprehensive two-dimensional gas chromatography (GC x GC) (both with flame ionisation detection) and gas chromatography-quadrupole mass spectrometry (GC-MS) analysis. Qualitative and quantitative aspects of the results are considered. Qualitatively, results from all chromatographic analyses are in good agreement, and PLE provides a reliable extraction technique with all PAHs extracted in one extraction step; no carry over was observed. With respect to PAH quantification, some variability in results was noted, with better agreement in PAH concentrations for GC and GC x GC measurement, as compared to GC-MS. GC analysis compares favourably with GC x GC apart from the few exceptions where peaks are not fully resolved from other co-extracted analytes, which compromises GC-FID measurement. For example, acenaphthene shows a much higher concentration when measured by GC-FID, demonstrating the superior separating powers of GC x GC; the latter is the preferred technique if precise and accurate quantification of analytes are required. GC-MS results compare reasonably with GC x GC for low-molecular mass PAHs but not for high-molecular mass PAHs; results for GC-MS are consistently higher than those for GC x GC for high-molecular mass PAHs. Since PLE-GC x GC is proposed as a broad screening tool, the demand for precise quantification may be relaxed in the present situation. GC x GC has the added advantage of providing chemical structural information within the two-dimensional contour presentation. Reproducibilities for GC x GC results (peak area) and 2tR were acceptable with relative standard deviations (R.S.D.) of 8 and 1%, respectively (at the mg/kg level), and good repeatability within samples was achieved.

Extraction and clean-up of contaminants and toxicants from food for mass spectrometric analysis--a literature review

This report presents a review of the literature on the extraction and clean-up procedures used prior to the analysis, by mass spectrometry, of organic contaminants and toxicants in foods and food-related materials. It includes a brief description of the uses of a mass spectrometer and shows how the mode of operation of the machine can influence the amount of clean-up necessary before a sample is presented for analysis. The review covers a variety of contaminants of different compound types in a wide range of foods and not only discusses sample preparation techniques that have been used for contaminant analysis by mass spectrometry but also considers some that could be used. The most commonly used techniques involve solvent extraction followed by a clean-up using liquid-liquid partition or column chromatography or both, although a number of newer methods being evolved are moving towards the ideal of a single-step extraction and clean-up process.