Recent Extraction Techniques with Emphasis on Supercritical Fluid Extraction and Microwave-assisted Extraction

Today’s requirements of fast, reliable and selective analytical methods with minimal usage of organic solvents have accelerated the development of new, automated extraction techniques. In this thesis recent extraction techniques with emphasis on supercritical fluid extraction (SFE) and microwave-assisted extraction (MAE) were investigated. Different environmental and industrial applications such as extraction of pesticides from process dust, active compounds in pharmaceutical tablets, mycotoxins in cereals and aromatic amines released from azo dyes in leather have been studied to outline advantages and limitations of the techniques. In all cases the extraction efficiencies were similar or better, solvent usage reduced and extraction times shortened compared to traditional extraction techniques such as sonication and liquid-solid extraction (shaking) procedures. Even though recent extraction techniques in most cases are superior to the conventional techniques, they differ in terms of selectivity, simplicity and sample throughput as discussed in this thesis. By utilizing an elongated trap in SFE further selectivity in the collection step was achieved for extractions of aromatic amines and for separation of fat-soluble vitamins from lipids. Devices to perform direct SFE of liquid samples were tested, resulting in a selective extraction of alkylphenols from real waste water samples. Furthermore, a fractionated MAE procedure including a reaction/extraction step was developed for the determination of amines after reductive cleavage of azo dyes in leather. A variant of pressurized liquid extraction (PLE) that utilizes water as extracting media is pressurized hot water extraction (PHWE). This technique was investigated for extraction of pesticides from process dust and obtained results were compared with results obtained using SFE. With better understanding of the characteristics of the recent techniques, conventional techniques can in most cases be replaced. In the future it is anticipated that combinations of different extraction techniques will appear in a single analytical method, where the inherent advantages of each technique are utilized. This was here demonstrated , where leather samples were degreased using SFE and further treated using MAE

Supercritical Fluid Extraction

Not available

Collection in analytical-scale supercritical fluid extraction.

This review is a comprehensive summary of available collection techniques in supercritical fluid extraction (SFE), with emphasis on which parameters are especially important for a successful analyte collection. Environmental, biological and agricultural applications, including several types of sample matrices and analyte groups, are discussed with respect to choice of collection mode and optimization of collection conditions. This review also includes discussions about collection when a modifier is used or when the sample contains large amounts of fat or water, as well as possibilities to achieve enhanced selectivity

Harmful azo colorants in leather. Determination based on their cleavage and extraction of corresponding carcinogenic aromatic amines using modern extraction techniques.

This study concerns the possibilities of using microwave-assisted extraction (MAE) or supercritical fluid extraction (SFE) for detection of harmful azo colorants in leather. After degreasing of the leather sample with SFE there follows a reductive cleavage of the azo colorants to their corresponding aromatic amines in the MAE or SFE equipment. The aromatic amines are subsequently extracted using either MAE or SFE and then finally determined by liquid chromatography with diode-array detection. The results have been compared with recoveries obtained using the German DIN method 53316. This standard method, based on conventional solvent extraction, is used in several European countries. Overall much better recoveries were obtained using MAE or SFE. With both MAE and SFE the amine recoveries of spiked leather samples were generally above 50%. The average recoveries were 62% for MAE and 60% for SFE (solvent collection) compared to 24% with the DIN method. For genuine leather samples the recoveries decreased, especially for benzidine. In this case the average values for MAE, SFE and DIN were 54, 38 and 19%, respectively. The quantification limits in leather samples using MAE or SFE were below 1 mg/kg for all amines investigated. The within-laboratory precision was generally better than 10%, varying somewhat with the analyte considered. With the proposed methodology, the amount of hazardous organic solvents used could be decreased and the sample throughput increased with at least a factor of two with less manual handling compared to the DIN method

Determination of banned azo dyes in consumer goods

Azo dyes, extensively used for coloring a variety of consumer goods, such as leather, clothes, food, and toys, can under certain conditions be reduced to form confirmed or suspected carcinogenic aromatic amines. This article gives an overview of the state of development of analytical procedures for the determination of such azo dyes, which are banned by the European Commission. (C) 2004 Elsevier Ltd. All rights reserved

Direct supercritical fluid extraction of alkylphenols from spiked and wastewater samples using extraction cells equipped with hydrophobic membrane-assemblies

Akylphenols (4-nonylphenol, 4-(1,1,3,3-tetramethylbutyl)-phenol and 2,6-bis(1,1-dimethylethyl)-4-ethylphenol) have been directly extracted from water samples using neat supercritical carbon dioxide and collected on an octadecyl silica (ODS) solid phase trap. The extraction cells were equipped with home-built assemblies containing hydrophobic membranes. The assemblies were inserted at each end of the extraction cell to maintain the water sample inside the extraction cell. In this case, no sample pretreatment step, such as freeze-drying or solid phase extraction (SPE) of the water samples, was needed prior to the supercritical fluid extraction (SFE). Distilled water, spiked with an alkylphenol standard solution at a level of 25 mg/L, was used as a model sample to investigate extraction efficiency as well as collection capability. To obtain quantitative recoveries, a fractionated extraction/clution procedure was adopted. The alkylphenols were finally determined in a leachate water sample and in an industrial effluent sample, where the levels were in the range of 0.2-10 mg/L

Microwave Assisted Extraction of Zearalenone in Wheat and Corn.

Abstract not availableJRC.I-Institute for Health and Consumer Protection (Ispra